THE 1992 CONGRESSIONAL HEARINGS!

THE UNIVERSITY OF TENNESSEE
MEDICAL CENTER AT KNOXVILLE
Drawer U-108
1924 Alcoa Highway
Knoxville, Tennessee 37920
(415) 544-9080

UNIVERSITY PATHOLOGISTS, PC Paul G. Googe, MD
Francis S. Jones, MD Dermatopathology
Anthony A. Kattine, MD Elizabeth W. Hubbard MD
Frances K. Patterson, MD Stuart Van Meter, MD
J. Michael McCoy, DDS Oral Pathology
D. Douglas Wilson, MD
Room # ICU 3
HOSP# 372709
PATH #S-309417
NAME: MILLER, PATRICIA BD/AGE:39 SEX: F DATE: 7-8-92
SOCIAL SECURITY NUMBER LEFT BLANK DOCTOR: CHASE
OPERATION PERFORMED: Total Christensen joint prosthesis replace R/L Christensen
SPECIMENS(S) SUBMITTED: A) Capsule L TMJ B) Scar tissue L C) Lymph node L
D) Pericondylar tissue L E) R capsule peri-implant
F) Scar tissue R G) Reactive condylar tissue R TMJ
H) Granulation tissue around neck of R condylar implant I) Granulation tissue, interface R condyle
J) Tissue R glenoid fossa area K) Tissue R mandibular condyle
PERTINENT HISTORY AND OPERATIVE FINDINGS: Bil TMJ dysfunction
PREVIOUS SURGICALS: S-205098, 217123, 242134, 262598,264849, 279092, 283417
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GROSS:
A) The specimen is labeled "left capsule" and consists of a single piece of blue-gray to gray-white, irregularly shaped soft tissue measuring 0.8 cm in greatest dimension. The specimen is bisected longitudinally and submitted in its entirety for histologic exam.
B) The specimen is labeled "scar tissue, left" and consists of a gray-white excisional biopsy measuring 4.5 x 0.5 cm, and extending to a maximum depth of 0.4 cm. The specimen is inked, serially sectioned in a transverse manner, and representative cross-sections are submitted in one cassette.
C) The specimen is labeled "lymph node, left" and consists of a light grayish-tan to dark reddish-purple, irregularly shaped lymph node with a small amount of yellowish adipose tissue attached, measuring 1.8 x 0.7 x 0.6 cm. The specimen is serially sectioned in a transverse manner and submitted in its entirety for histological exam.
D) The specimen is labeled "pericondylar tissue" and consists of two pieces of blue-gray irregularly shaped soft tissue. The largest is elongated and measures 1.2 cm in greatest dimensions, the small measures 0.7 cm in greatest dimensions. The specimens are submitted in their entirety for histological exam.
(193)
E) The specimen is labeled "right capsule" and consists of a single piece of light blue-gray irregularly shaped soft tissue measuring 0.8 cm in greatest dimensions. Specimen submitted in its entirety for histological exam.
F) The specimen is labeled "scar tissue, right TMJ" and consists of a gray-white excisional biopsy measuring 4.1 x 0.2 cm, and extending to a maximum depth of 0.25 cm. The specimen is inked, serially sectioned in a transverse manner, and representative cross-sections are submitted in one cassette.
G) The specimen is labeled "reactive condylar tissue, right TMJ" and consists of a single piece of light grayish-tan to dark grayish-tan, irregularly shaped, soft tissue, measuring 1.3 x 1.0 x .06 cm. The specimen is bisected and submitted in its entirety for histological exam.
H) The specimen is labeled "granulation tissue around neck of right condylar implant" and consists of four pieces of grayish-tan tissue. The largest measures 0.6 cm in greatest dimension, the smallest measures 0.15 cm in greatest dimension. Specimen is submitted in its entirety for histological exam.
I) The specimen is labeled "granulation tissue interface right condyle" and consists of five pieces of dull gray-white, dark blue-gray, irregularly shaped, soft tissue. The largest measures 1.4 x 0.7 x 0.6 cm, the smallest 0.3 in greatest dimensions. Specimen submitted in its entirety for histological exam.
J) The specimen is labeled "tissue right glenoid fossa" and consists of two pieces of light grayish-tan to blue-gray, irregularly shaped soft tissue. The largest measures 0.8 cm in greatest dimensions, the smallest 0.5 cm in greatest dimensions. Specimens submitted in their entirety for histological exam.
K) The specimen is labeled "tissue right mandibular condyle" and consists of a single piece of pale yellow to glue-gray, irregular shaped soft tissue measuring 1.5 x 0.9 x 0.8 cm. The specimen is bisected longitudinally and submitted in its entirety for histological exam.
DH/gbs (194)
MICROSCOPIC
Specimen A consists of a connective tissue which is quite hyalinized in areas. Portions of it is quite hypercellular with numerous darkly stained foreign bodies surrounded by foreign body type giant cells encountered.
Specimen B consists of hyalinized fibrous tissue and hair bearing skin without atypia.
Specimen C consists of multiple fragments of salivary gland. The gland shows mostly serous acinar structures and significant infiltration by fat. There are also numerous mucous acini identified.
Specimen D consists of fibrous connective tissue within which are found a few darkly pigmented foreign bodies showing very little in way of reaction.
Specimen E is fibrous connective tissue with only a few scattered foreign bodies surrounded by giant cells.
Specimen F is hair bearing skin which shows no abnormalities.
Specimen G is a lymph node within which are found numerous foreign body giant cells surrounding engulfed fragments of darkly pigment foreign material.
Specimen H is connective tissue showing small particulate foreign body surrounded by giant cells.
Specimen I is consistent with connective tissue showing an intense infiltration by darkly pigmented foreign material much of which is surrounded by foreign body giant cells.
Specimen J is hypercellular connective tissue within which are found numerous histiocytes and giant cells. There is also significant synovial hyperplasia identified in these sections.
(195)
Specimen K demonstrates a diffuse histiocytic proliferation and scattered giant cells.

DIAGNOSES:
A) "Left capsule": Intense foreign body reaction
B) "Scar tissue, left": Unremarkable skin, no foreign bodies seen
C) "Lymph node, left": Submandibular salivary gland unremarkable
D) "Pericondylar tissue": Scar tissue with minimal foreign body reaction
E) "Right capsule": Scar tissue with minimal foreign body reaction
F) "Scar tissue, right": Skin, no foreign bodies seen
G) "Right TMJ tissue" Lymph node with discrete foreign body granulomas
H) "Right granulation tissue": Foreign body reaction
I) "Right condyle granulation tissue": Foreign body reaction
J) "Right glenoid fossa": Synovial hyperplasia with foreign body reaction
K) "Right mandibular condyle": Diffuse foreign body reaction
signed
J. Michael McCoy, D.D.S.
JMM:adj Pathologist
07/13/92

Date signed 7/13 phone report_____ date/time charted_________
(196)




Subj: CH#22

APPENDIX 2. -REVIEW ARTICLES ON ALLOPLASTIC IMPLANTS
Disorders of the TMJ II: Arthrotomy 1042-3699/89 $0.00+.20

ALLOPLASTIC IMPLANTS IN THE TEMPOROMANDIBULAR JOINT
DORAN E. RYAN DDS, MS*

The generally accepted indications for removal of the articular disk from the temporomandibular joint (TMJ) include intermediate-to late-stage anterior and medial displacement where the disk demonstrates loss of normal morphology with shortening of the anteroposterior dimension, central perforation, or fragmentation beyond repair. The histologic morphology of the disc in these advanced stages of disease was described by Grote and coworkers. 20 Loss of collagen fiber orientation and the presence of chondrocytes, cartilage, and vascularity were noted. Synovitis, synovial hyperplasia, and fibrous adhesions have been seen by arthroscopy in these late-stage cases. Alteration of the articular surfaces with fibrillation, exposed subchondral bone, and degeneration can follow. 41 As the dysfunction progresses, myofascial pain and parafunctional habits tend to increase.
These are the difficult surgical cases! These are the cases in which alloplasts have been recommended and utilized. In this situation, should alloplastic interpositional materials be abandoned, or are our expectations for success with these materials too high? In trying to answer this question, it is important to review carefully the use of interpositional implants, not only in the TMJ but also in other joints of the body. Microscopic analysis can be performed on removed clinical specimens, arthroscopic biopsy material, and animal tissues. Success can best be evaluated by long-term clinical and radiographic follow-up of the various TMJ alloplasts. This article presents such information from which the reader can reach his or her own conclusions regarding the efficacy of these products.
PROPLAST-TEFLON
Proplast is the porous form of Teflon (polytetrafluoreoethylene;PTFE) and has been fused with either vitrous carbon (Proplast I), aluminum oxide (Proplast II), or synthetic hydroxyapatite (Proplast HA). The interpositional implant is a laminate of either Prolast I or Proplast II and Teflon. The Proplast portion, placed against the temportal bone or periosteum, is designed to encourage ingrowth of tissue to stabilize the implant. The smooth Teflon functions against the condyle. As of this writing, the Proplast-Teflon interpositional implant can no longer be purchased, but it has been used more 20,000 surgical cases since 1983. Success rates have been reported to range from 93 to less than 50 per cent. 17, 27
EARLY USE OF TEFLON
Calnan,6 in 1963, attempted to establish standard of quality for the use of foreign materials in reconstructive surgery. He pointed out that movement can be a problem and ultimately leads to failure. This important finding was a factor in the development of the Proplast-Teflon laminate. He also evaluated the tissue reaction to different materials, looking at round cells, macrophages, and giant cells and the fibrous reaction, including capsule formation around-cont'd
______________________________________________________________________
*Associate Professor and Chairman, Department of Oral and Maxillofacial Surgery. Medical College of Wisconisn, and Clinical Professor of Oral and Maxillofacial Surgery. Marquette University School of Dentistry, Milwaukee, WIsconsin
Oral and Maxillofacial Surgery Clinics of North America-Vol. 1. No.2 December 1989
(197)
the implant. The PTFE was the least reactive; in fact, the smooth form was without giant-cell reaction. Although PTFE produced less fibrous reaction than the other materials, a complete capsule was formed. Calnan concluded that the "tissue reaction to PTFE is less than with any other material and for this reason it is recommended that the use of all less satisfactory material should be discontinued." The PTFE used in this study was not medical grade; it was obtained from the Crain Packing Company.
In 1960, Charnley8 described the use of PTFE as "synthetic cartilage" in total and partial hip replacements. He measured the coefficient of friction between bone and substances commonly used in arthroplasty and concluded that the only solid that remotely approached articular cartilage was PTFE (another important factor in the development of the Proplast-Teflon laminate). Experiments on dogs having hip prostheses with Teflon parts were conducted by Leidholt and Gorman.30 The Teflon cup showed wear and deformation after an average of 8.7 months. The surrounding capsule and synovium were grossly thickened, and all animals showed acute and chronic inflammation of the joint tissues, in which were found Teflon particles. Giant cells were frequent, indicating a foreign-body reaction. Those investigators could not determine whether the particle size or some characteristic of the local tissue was the principal factor in the reaction. Similar results were observed in an implant taken from the patient of one of those authors. Leidholt and Gorman felt Teflon should not be used in weight-bearing joints.
Charnley and Kamanger stopped using Teflon for hip sockets in 1963 and reported on the results in 1969.9 They stated that the most serious aspects of the failure of PTFE was the production of tissue reaction by wear debris, which caused loosening of the socket by erosion of the bone. They believed the particles were produced too fast for the tissues to dispose of them.
ORAL AND MAXILLOFACIAL SURGICAL EXPERIENCE
The first published use of Proplast-Teflon interpositional implants in the TMJ was in 1982. Gallagher and Wolford18 had placed 10 implants in the TMJ over the previous 4 years with good results. These implants were placed between the condyle and the meniscus after condylectomy and wired to the condyle. Silastic was used in the same manner in nine joints with three failures secondary to breakage of the ligature wire and herniation of the implant through the capsule. Those authors felt the Proplast-Teflon was a better implant because ingrowth of fibrous tissue led to better stability.
Earlier, Homsy and associates 26 had demonstrated the ingrowth of fibrous tissue into PTFE-pyrolytic graphite with porosity between 70 and 80 per cent and pore size between 100 and 500 pm. Interbridging between pores of greater than 200 pm would allow for bone growth, which was deemed important to prevent movement. Homsy and coworkers25 noted the presence of giant cells around the implants but did not know the significance, suggesting that it might be secondary to mechanical stimulation. In a presentation to the US Food and Drug Administration in 1989.50 Homsy again recognized the presence of macrophages and macrophage polykaryons around the implants but felt such "findings are nonmorbid" and, in fact, may contribute to normal healing. He pointed out that fragmentation and motion will increase the number of foreighn-body giant cells. Secretory products of macrophages and their functions were reviewed in 1984 by Takemura and Zena, 48 who pointed out that if the macrophages are able to control the foreign material, they become central in tissue repair. When they are unable to control the foreign material, macrophages may inadvertently participate in excessive tissue destruction by secreting neutral proteinases and acid hydrolases.
The clinical success of Proplat-Teflon interpositional implants was highly touted in the early 1980s. Kiersch27 reported a 93 per cent success rate over 9 years for 250 implants used for both disk repair and replacement. Carter, 7at the 1983 national meeting of the American Academy of Oral and Maxillofacial Surgeons, reported an 87 per cent success rate on 52 patients over a 3-year period using Proplast-Teflon as a meniscus replacement. Merrill,32 in a 1985 survey of 37 TMJ surgeons as to their selection of surgical procedures for meniscectomy and interpositional implants, found that 34 felt there was an indication for disk removal and 15 of those favored Proplast-Teflon implants because of the lesser likelihood of displacement. In 1986, Vitek, Inc. conducted a written survey among oral and maxillofacial surgeons who performed TMJ surgery to compare techniques and results. Of these, 259 surgeons had used Proplast-Teflon implants in 5070 cases with a 91.5 per cent rate of satisfactory results. No guidelines for defining success were discussed. Moriconi and colleagues34 identified Proplast im-
(198)
plants as "a more predictable mode of temporomandibular joint reconstruction." Again, ingrowth of tissue into the Proplast was felt to be of the utmost importance. Close follow-up was called for to "adequately assess the performance" of these implants. No results were presented.
Problems with Proplast-Teflon interpositioned implants were first identified in writing by this author in a Temporomandibular Joint Newsletter from the Medical College of Wisconsin in 1985. On recall Examination, development of an anterior open bite was noted in 20 per cent of the patients, as was occasional continued degeneration of the condyles. The etiology of this problem was not identified. Using New Zealand rabbits, Timmis and coworkers49 replaced the meniscus with either silicone or PTFE-Al2O3 implants. The Proplast-Teflon group demonstrated marked osteoclastic activity with resorption and severe degenerative changes in both the condyles and glenoid fossa, and implant tearing was seen in 46 per cent of the joints. Lymph node involvement with collections of Teflon particles, multinucleated giant cells, histiocytes, and granulation tissue was described by Lagrotteria and colleagues.29 Breakdown of a Proplast I implant with perforation and extensive giant-cell reaction was found in the ipsilateral TMJ. The largest particle found in the node was a carbon fiber of 42 pm. The Proplast-Teflon fragments were only a few micometers in diameter. An implant examined via arthroscopy by Bronstein5 "was seen to be in good condition and not fragmented or damaged; however it was not covered with soft tissue." The implant had been in place for 3 months., and the patient's complaint was increased noise. In the same paper, 38 patients with 20 silicone and 18 Proplast II implants were evaluated with tomographic studies. The Proplast-Teflon implants produced more severe bony responses with erosion of both condyle and fossa. Florini and coworkers17 followed 55 PTFE- and 18 diskoplasty-treated joints for 20 months and 48 months, respectively. More than 60 per cent of the joints with Proplast-Teflon implants showed severe, destructive osseous changes, whereas none of the joints managed by diskoplasty showed such changes.The authors speculated that if the size and number of particles exceeded the capacity of the lymphatic system to remove them, the reaction in the joints themselves would be one of destructive arthritis. In 1989, EL-deeb and associates15 investigated Proplast implants in non-weight bearing areas. Fragmentation and giant-cell formation wre shown, along with collapse of the Proplast and loss of the interbridging fibrous tissue connections. No bone growth was demonstrated. This lack would tend to decrease stability, which may account for the increased giant-cell reaction. Speculation would suggest a similar phenomenon when Proplast is used in a weight-bearing area such as the TMJ.
MEDICAL COLLEGE OF WISONSIN EXPERIENCE with PROPLAST II
Over a 25-month period, 105 TMJ procedures on 67 patients were performed at the Medical College of Wisconsin. In the retrospective clinical and radiographic analysis, 13 patients with 19 TMJ procedures wre excluded from this survey because of incomplete medical records. The sample group was divided into subgroups: a primary group of 36 patients with no previous surgery, and a secondary group of 18 patients who had had previous Silastic implants (Table 1). All 54 patients met the criteria for surgical treatment. Similar to other reports, 90 per cent of the patients were women, and the average age was 30 years.
All operative procedures were performed through a standard preauricular approach. In the primary group, a diskectomy was performed because it was deemed technically impossible to repair the disk. Additionally, eminoplasties were performed in all cases to reduce the height and change the slope of the eminence in the hope of reducing the pressure against the implant during function. After diskectomy, a 1.3-min PTFE-aluminum oxide fossa implant was sized to cover the fossa and the articulating surface of the eminence. The implant was fixed to the lateral rim with either 2-0 Mersilene sutute or multiple lateral stainles steel wires. Both prior to and following fixation of the implants, simulated articulation and function of the joints were performed to ensure that the implants did not displace.
Table 1. STUDY GROUPS RECEIVING PROPLAST II (PTFE-AL2O3) IMPLANTS, OCTOBER 1983 TO NOVEMBER 1985
NO. OF PATIENTS TOTAL
UNILATERAL BILATERAL JOINTS
Primary group (diskectomy
Proplast II ) 17 19 55
Secondary group (Proplast
II after Silastic failure) 5 13 31
(199)
Table 2. Number of joints with Radiographical and Surgical Evidence of Arthrosis, Preoperatively and at Exploration
None Mild Marked Severe
Primary Group
Preoperatively (n=55) 31 24 - -
Proplast II failure* (N=44) - 3 22 19
Proplast II in situ
Stable (n=9) - 6 3 0
Unstable+ (N=2) - - - 2
Secondary group
Preoperatively (N=31) - 24 5 2
PROPLAST II failure (n=26) - - 11 15
Proplast in situ
Stable (N=3) - 1 2 -
Unstable (N=2) - - - 2
*Implant removed +Implant should be removed

In the secondary group, 31 reoperations were performed because of failure of previously placed Dacron-reinforced Silastic fossa implants after diskectomies. The surgical procedure in all cases consisted of removal of the fossa implants, debridement of the soft tissue including all reactive tissue in the joint space, and, when necessary, minimal bone plasty to smooth areas of degeneration on either the condyle head or the eminence. After debridement and bone plasty, PTFE-aluminum oxide implants were placed as described.
Preoperatively, 68 per cent of the patients exhibited a class I occlusion, 26 per cent a class II malocclusion, and 3 per cent a class III malocclusion. The other 3 per cent were edentulous. In the primary group, 38 per cent of the patients exhibited no symptoms or physical findings of myofascial pain, and 62 per who did have symptoms and physical findings of myofascial pain, 92 per cent had splinting preoperatively and postoperatively. In the secondary group, all except one patient presented with signs and symptoms of myofascial pain, and all of these patiens had splinting both preoperatively and postoperatively.
Finally, an assessment was made for radiographic or surgical evience of arthrosis preoperatively or at the time of exploration of the joint in the primary group, 56 per cent of the joints exhibited no evidence of arthrosis, and the remainder had only mild degerative changes, that is, minor flattening or a localized loss of articular surface at the site of perforation (Table 2). In the secondary group, 77 per cent of the joints showed mild degenerative changes, 16 per cent proved to haved marked changes, and 7 per cent showed severe changes (Table 2).
All patients were recalled via certified mail with follow-up mailing if no response was received. In the primary group, 28 of the 36 patients met the criteria for implant failure (discussed later in this article) and had their implants removed, a 77 per cent failure rate (Table 3). In the secondary group 15 of the 18 patients met the criteria for failure, and , again, the implants were removed. The average time from placement to removal of PTFE implants was 30 months in the primary group and 29 months in the secondary group (Table 4).
Regarding occlusion and rate of failure, patients in class I had greater success with the implants, but the failure rate was so high in all groups that statistically, there was no difference. This held true for both the primary and the secondary groups. In the primary group, there was a lower failure rate when myofascial pain was absent preoperatively. The use of splints postoperatively. The use of splints postoperatively also seem to improve the success rate. Unfortunately, the failure rate was high with all combinations of symptoms and adjunctive measures. The lowest failure rate, 66 per cent, was in those patients without preoperative myofascial pain who utilized splints after surgery. In the secondary group, all but one patient had signs or symptoms of mysofascial pain before surgery, so no comparison could be made in this group.
Comparison of the radiographic and surgical appearance of the joints preoperatively with that at the time of the last implant evaluation showed a significant change (see Table 2). All 31 of the joints in the primary group that demonstrated no arthrosis before surgery had evidence of advanced arthrosis, with 84 per cent classified as having marked to severe chamges. ALl the original mild arthroses had become marked or severe. In the secondary
Table 3. Failure Rates of Proplast II Implants
Numbers (Per cent) of Failures
Unilateral Bilateral Total Joints Total Patients
Primary
Group 12/17 (70) 16/19 (84) 14/55 (80) 28/36 (77)
Secondary
Group 4/5 (80) 11/13 (84) 26/31 (83) 15/18(83)
(200)
Table 4. Number of Proplast II Implants Removed at Various Times after Placement
Months Primary Secondary
After Placement Group Group
4-12 - 3
8-12 5 -
13-24 10 5
25-36 14 8
37-48 13 10
49-51 2 -

group, there was a shift of the arthrosis from the mild and marked category preoperatively to the marked and severe category at the last evaluation.
Magnetic resonance imaging (MRI) was used to evaluate many of the implants before removal. In the cases with severe arthrosis, loss of signal in the condyle, loss of temporal bone, presence of large soft-tissue masses, and fragmentation of the implants (PTIPI) were often identified (Fig. 1). At surgery, all implants were found to be perforated (Fig. 2), 50 per cent exhibited folding, and 17 per cent were fragmented or separated into their two components. Perforation through the temporal bone with exposure to the dura of the middle cranial fossa was found in four cases. (Fig 3).
Histologic studies of the peri-implant tissue consistently showed a fibrous background with exuberant foreign-body giant-cell reactions. Numerous darkly staining foreign-body fragments were always seen, with giant cells surrounding the foreign material (Fig. 4). Secondary characteristics inluded focal areas of chronic inflammatory cells such as lymphocytes, plasma cells, and occasional histocytes.
SILICONE
EARLY USE
Silicone in various forms has been used by many surgeons for prevention of ankylosis. 1 11,16,23,31,37,43,61 The long-term results or complications of the use of this material were seldom discussed. The first mention of the use of silicone as a disk substitute was in 1969, when Henny 24 recommended Silastic sheeting be used after condylectomy if the perforation of the meniscus was extensive. The success rate of the procedure and long-term follow-up findings were not discussed. The first documented clinical and radiographic follow-up of interpositional silicone implants also appeared in 1969. 22 Four patients, one with bilateral procedures, were followed after the implantation of a silicone sponge, 3 to 4 mm thick, which was sewn to the capsular soft-tissue structures. At 3 years, all patients demonstrated normal joint space with a slight decrease in the motion of the condyle and no pain. In 1970, Habbi and associates21 described the creation of surgical fractures below the condyle in rabbits and placement of either Silastic or Supramid (sulfa-
Insert picture A Insert picture B
Figure 1. MRI images of PTIPI implants a. Scan of left TMJ showed decreased signal of condyle (C), fragments of PTIPI (small arrows), soft-tissue mass surrounding the implant (M), and loss of temporal bone (T) with mass against the dura (large arrow). The mass does not involved the ear canal (EC). B. Scan of the TMJ with fragmentation of the PTIPI implant (arrows), severe degerative changes and decreased signal of the condyle (C), and a large mass surrounding the implant (M). THe temporal bone (T) is intact, and the mass is not affecting the ear canal (EC).
(201)
insert picture Figureii. Perforated PTIPI with a soft tissue mass still
attached to the lateral aspect around three stainless steel wires (left)
meter) as interpositional materials. The materials produced similar histologic results, with chronic inflammation the first weeks and then diminution with time such that minimal reaction was noted at 6 weeks. A fibrous connective tissue lining was observed around the pseudoarticulation. Detailed histologic information was not availabe. A follow-up study by Murname and Doku36 of the same rabbit population found capsular formation around the pseudoarticulation lined with synovial-type tissue and the presence of synovial-type fluid. A slight foreign-body giant-cell reaction was also noted.
ORTHOPEDIC EXPERIENCE
Silicone has been used as a spacer between joint surfaces by the orthopedic community since the early 1960s. Evaluation of these im-

insert picture Figure 3. Looking into the glenoid fossa, the dura (arrow) of the medial cranial fossa is seen through a temporal bone perforation.
(202)
insert picture
Figure 4. Particles of the PTIPI (small arrows) surrounded by giant cells (large arrows)
and other phagocytic cells.
plants, the complications that can follow, and the controversy surounding their use thus precedes our experience by about 10 years. In 1962, Swanson45 introduced a metacarpophalangeal and interphalangeal joint prosthesis made of silicone. Since that time, silicone has been used in almost every joint of the body, including the big toe. Complications such as infections, dislocations, fractures, and dentritic synovitis have been reported. Fracture rates of the implants range from 1 per cent 46 to 26 per cent.2
The first report of silicone lymphadenopathy secondary to fractured implants in the hand was published in 177.10 The mean maximum diameter of the silicone particles in the nodes was 24.5 pm. Benjamin and associates3 in 1982 reported two cases of silicone lymphadenopathy, one with concomitant malignant lymphoma. Fracture of the implants on the ipsilateral side was not always found in these cases. The occurrence of lymphoma in a patient with Silastic arthroplasty was probably fortuitous considering that patients with rheumatoid disease have an increased instance of malignant lymphoma. In 1983, Smahel and Meyer44 examined the capsules around Silastic implants used in hand surgery. They found a collagen structure that matured in 2 months at the latest and thereafter changed little as time passed. The capsule from around joint prostheses had a slightly less closely packed inner layer of connective tissue containing numerous foreign particles surrounded by macrophages and multinucleated giant cells. At times, a pseudoepithelium containing multinucleated giant cells accumulated at the inner margin. Autopsy tissue from three dogs and one patient who had silicone implants in place for 12 and 10 years, respectively, was examined by Nalbandian and coworkers.36 Again, the uninflamed capsule contained scattered areas of lymphocytes, macrophages, and multinucleated giant cells in a connective tissue stroma. Macrophages and giant cells were adjacent to silicone particles. All organs of the dogs were examined for silicone, and none was found. The human tissue was similar histologically except that silicone was found in one axillary node and in the subsynovial connective tissue. No acute inflammation was noted in any specimen. Those authors noted that Dacron suture provoked a reaction both quantitatively and qualitatively similar to that induced by the silicone particles. Swanson, 46 in a clinical experience of 3,000 pa-
(203)
tients, found silicone foreign-body synovitis in less than 1 per cent and lymphadenopathy in 0.01 per cent of such cases. In 1984, Swanson and coworkers 47 reported that in a 4-year follow-up of 175 wrist silicone implants, 12 per cent had required replacement and 16 per cent had fractured. Radiographic remodeling was found, but no evidence of tissue intolerance to the silicone elastomer was noted.
Since 1984, many articles have discussed the advantages and disadvantages of silicone in joint arthroplastic procedures. Bone resorption and cystic osteolysis secondary to fragments of silicone have been reported.14,36 Introduction of high-performance medical-grade silicone has decreased the complications, but they still occur.42 In general, the orthopedic community understands the advantages and disadvantages of silicone and uses the products when and if they feel it is appropriate.
ORAL AND MANILLOFACIAL SURGICAL EXPERIENCE WITH SILICONE INTERPOSITIONAL IMPLANTS
In 1981, Sanders 40 presented a large series of silicone implants wired to the glenoid fossa. The early results were excellant. In 1983, Bessette4 reported the results of Silastic block implants sutured to the soft tissues of the TMJ after partial meniscectomy in both monkeys and humans. Of the 62 patients treated, 87 per cent obtained relief of symptoms, and 62 per cent had increased range of motion. In 4 of the 10 animals only a mild tissue reaction was demonstrated. In the other 6 animals, mild to moderate chronic inflammation was seen only immediately adjacent to the implants. No adverse effects on condylar growth were noted. Ryan, 30 at the 1984 Clinical Congress, reported an 89 per cent success rate in 150 patients (185 joints) after meniscectomy and replacement with Dacron-reinforced Silastic wired or sutured to the glenoid fossa and eminence. The average follow-up was 1.5 years. This retrospective study included range of motion of the mandible, a comparison of preoperative and postoperative pain, ability to eat, and determination of the success rate based on specific guidelines (Table 5). Merrill, in 1986,33 reviewed 69 patients who had meniscectomy and Dacron-reinforced Silastic sutured to the fossa eminence and reported a 91 per cent success rate, In a histologic evaluation of the TMJ soft tissues after removal of failed Silastic implants, Dolwick and coworkers13 found a foreign-body giant-cell reaction around fragments of Silastic dispersed throughout the tissue. The following year, two of the same investigators 12 reported the presence of cervical lymphadenopathy on the side of a Silastic implant in the TMJ. A biopsy specimen showed a silicone-induced foreign-body giant-cell reaction in the node.
By 1985, many surgeons had given up using permanent Silastic and had gone to to Proplast-Teflon laminates, as reportedly by Merrill in his survey, 32 Only five surgeons were using permanent Silastic implants; two others were using thin Silastic sheets as a temporary implant, removing them 2 to 5 months after placement. In 1986, Timmis and coworkers49 compared Silastic with Proplast-Teflon implants in the TM of rabbits. Many of the Silastic implants became displaced, and wear particles were found throughout the soft tissue of the joint. The bone reaction was mild to moderate compared with the moderate to severe reaction secondary to the Proplast-Teflon implant. Clinical and readiographic evaluation of 20 Silastic implants was discussed by Bonstein.5 Patients were generally pleased with the function, although in many cases, his criteria for success were not satisfied. Radiographic examination showed less disturbing bone erosion responses than those seen with the Proplast-Teflon implants. He also pointed out that bony apposition and osteophyte formation may be seen in joints in which Silastic implants have been placed.
MEDICAL COLLEGE OF WISCONSIN EXPERIENCE with SILASTIC IMPLANTS
A survey with 14 questions was sent to all patients treated by meniscectomy and interpositional Dacron-reinforced Silastic implants at the Medical College of Wisconsin since 1982. The criteria for initial surgery were pain in the joints, dysfunction with radiographic evidence of internal joint derangement, and unwillingness of the patient to live with his or her present quality of life. Nonsurgical therapy was made available to all patients. Occasionally, when mechanical dysfunction of the joint was severe, a patient would elect not to pursue nonsurgical therapy. The total number of patients surveyed was 215, of whom 98 responded to the the survey, cont'd on 205

Table 5. Minimun Criteria for Implant Success
Vertical movement 36mm
Lateral movement 5 mm
Protrusive movement end to end
Pain relief 85 per cent
(20)
42 had not responded at the time of this writing, 69 had moved with no forwarding address, three were deceased, and two returned the survey without a name. Adequate records were not available for one respondent. The average follow-up was 5 years, 3 months (range 1 year, 6 months to 8 years).
Because 40 per cent of the patients have had their implants removed, the 98 evaluable patients were divided into two groups: group 1 with the implants still in the joint and group 2 with the implants removed.
Of the 62 patients in group 1, 33 (53 per cent) reported no pain. The remaining 29 patients graded their pain from 1 (no pain) to 10 (most intense pain imaginable). Their present pain average was 2.7, and their usual pain was 2.6 (Table 6). All 62 patients also rated how they felt now compared with the time they were treated using a scale of -7 to +7, with 0 being the original condition. The average score was +4.1, with 13 per cent being worse after treatment (Table 6).
Two questions related to chewing ability. In these, patients graded their chewing from 1 (no difficulty) to 10 (unable to chew). The average in group 1 was 2.2, with 42 per cent having no difficulty at all (Table 7). Patients were also asked to rate how they chewed now compared with when they were treated. The scale was from -7 to +7, with original ability to chew being 0. The group 1 average was +4.5, with 11 per cent worse, 6 per cent the same, and 82 per cent better (Table 7). Seven yes or no questions also were asked (Table 8).
In Group 2, those with implants removed, the results were not quite as good. Only 7 patients (19 per cent) had no pain, and the remaining 26 patients graded their present pain at an average of 3.8 and their usual pain at an average of 4.3 (Table 6). Almost one fourth (21 per cent) were worse since treatment. 44 per cent graded their condition +5 to +7 (table 6). The average chewing ability was graded 3.5, with 17 per cent having more difficulty chewing since treatment and 71 being better off. Continued from page 205
Table 6. Patient assessment of Results of Silastic Implants
GROUP 1 GROUP 2
PAIN (SCALE 1-10)
Present 2.7 (N=29) 3.8 (N = 26)*
Usual 2.6 4.3
Perceived conditions relative to
preoperative state number (%)
Feel better 53 (87) 26 (76)
z + 5t 45 (74) 15 (44)
Feel worse 8 (13) 7 (21)
s -5 3 (5) 4 (12)
Same 0 1 (3)
______________________________________________________________________
*Averages were calculated from scores only from these patients reporting pain
T Scale +7 to -7 with 0 being condition at time of treatment.

Half graded their chewing+5 or better (Table 7). On the other measures of outcome, again, group 2 did not fare as well as group 1 (Table 8).
If the two groups combined, 40 of 89 patients (40 per cent) were pain free and 60 patients (61 per cent) had little or no pain at the time of the survey. Almost 83 per cent were improved by surgery, whereas 16 per cent were worse off and one patient was unchanged. Ability to chew was improved in 78 per cent of the patients and made worse in 13 per cent.
The patients in both groups also were asked to mark the areas of pain on line
drawings of the left and right sides of the face. These data have not yet been analyzed; in a future publication, we will try to separate the myofascial pain from the joint pain.
TABLE 7 Patient Assessment of Postoperative Chewing Ability
Group 1 (%) Group 2 (%)
Average ability to chew* 2.2 3.5
No difficulty 26/61 (42) 9/34 (26)
Unable to chew 0 (3)

Perceived ability relative to
preoperative condition
Better 51/62 (82) 25/35 (71)
z + 5t 46 (74) 19 (54)
Worse 7 (11) 6 (17)
z -5 1 (2) 3 (9)
Same 4 (6) 4 (11)
______________________________________________________________________
*Scale 1-10
t Scale +7 to -7 with 0 being condition at time of operation.

Table 8. General Function in Patients Receiving Silastic Implants

PER CENT REPORTING PROBLEM
GROUP 1 GROUP 2
(N= 62) (N=36)
______________________________________________________________________
AWAKENED BY PAIN 11 34
Clenching or grinding 40 63
Pain worse on functioning 37 71
Limited opening 41 49
Dietary limitations 31 61
Joint noises 60 89
Locking 8 28
(205)
ANIMAL STUDIES
From October 1982 to June 1984, the TMJ disks of 15 Macaca mulatta monkeys were removed bilaterally and either not replaced or replaced with Dacron-reinforced Silastic or Proplast II. On one side, a condylar shave was accomplished, and on the other side, every attempt was made to avoid the articular surfaces. All monkeys survived the operation without adverse incident and were started on normal diets within 48 hours. Masticatory function was noted to be unhindered in all animals.
Before euthanasia of the animals, a clinical examination utilizing general anesthesia tested for mandibular range of motion. One monkey with bilateral diskectomies without implants demonstrated restricted opening; three others had limited range of motion in lateral and excursive movements; two of these had Silastic and one a Proplast-Teflon implant. Joint noises were present in all animals except one with Silastic implants.
On histologic examination, a well-defined connective tissue capsule was found surrounding all implants. The functional load-bearing area at the center of the implant showed various degrees of wear (Fig. 5). All of the implants but one Silastic were torn. Microscopic fragments of the implants were found throughout the fibrous tissue capsule and in the marrow of the condyles of two animals with Silastic implants and the one with the Proplast-Teflon implant. The fragments were surrounded by giant cells. In the two monkeys in which no alloplastic replacement was used, a florid growth of fibrous tissue was noted within the joint spaces. This tissue displayed a less organized pattern that was seen in animals with alloplastic replacement. On the condylar shaved side of these specimens, fibrous ankylosis was seen. In the animals with implants and a condylar shave, a cap of the interpositional fibrous tissue had scarred to the condyle (Fig. 5B). The contralateral joint displayed a more distinct separation of periosteum and fibrous tissue. (Fig. 5A). In the 1-year, 3 month specimen in which Proplast-Teflon was used, a large giant cell mass accumulated anteromedial to the condyle (Fig.6A). Particles of the Proplast -Teflon were contained within this mass (Fig. 6B). The results of this study (GE Clark, ET Rippert, GE Nieusma, DE Ryan, unpublished) were consistent with the findings of the other animal studies previously discussed.
DIAGNOSIS OF FAILING ALLOPLASTIC IMPLANTS
Clinical follow-up is paramount! Swelling around the joint, increasing pain in the joint with function, decreased range of motion, and increasing noise suggest a breakdown of the implant. Occlusal changes, especially development of an open bite, mandate further evaluation. Changes in joint noises, especially crunching or grinding sounds, may signal fragmentation of the alloplast. Panoramic radiographs will document any bony changes in the joint and many times will verify implant position or displacement. Remodeling of the bone is no unusual and in fact is expected, but irregular changes with loss of cortical margins are pathologic and warrant further investigation. Magnetic Resonance imaging28 is the only technique that evaluates both the soft tissues surrounding the implants and the condition of the implants (Fig 7A). Wear of the implant (Fig. 7B), increased soft-tissue formation (see Fig.1B), and fracture of the alloplast (Fig. 7C) can be identified. Increased soft-tissue reaction around the Silastic noted by MRI, is rare, whereas such a reaction around Proplast-Teflon is not unusual and may preclude the clinical sign of occlusal changes. If the implant has fractured, the patient should be informed, and, if he or she concurs, the implant should be removed.
Silastic, which will not bind to the tissues of the joint, is easier to remove than Proplast-Teflon. In our experience, Proplast-Teflon has always demonstrated some degree of soft-tissue adherence. Any inflammatory tissue, which usually appears brown or yellowish and granulomatous, should be removed. Unless a concerted effort is made to remove all of the abnormal tissue containing fragments of the implants, the foreign-body reaction may continue (D Chase, personal communication). reconstruction of the joint following removal of the implant is discussed elsewhere in this issue.
SUMMARY
Although Proplast-Teflon interpositional implants are no longer available, for use, many patients still have them in place. All such patients must be contacted and thoroughly evaluated. In our experience, 80 per cent of the implants were removed, and all were found to be damaged. Unused implants should be returned to the manufacturer.
In our study, 40 per cent of the Silastic
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INSERT TWO PICTURES-FIGURE 5
Figure 5. Sagittal sections through the left TMJ of a monkey 15 months after Silastic implant. A. Animal without a condylar shave. Both joint spaces are preserved, along with a synovial lining (curved arrows). The implant space (S) is surrounded by a connective tissue capsule (short arrow) with a small perforation (long arrow). Minimal bony changes of the condyle (C) or temporal bone (T) are seen. The posterior attachment (PA) and lateral pterygoid (P) are also identified. B. Animal with a condylar shave. The inferior joint has been lost, an osteophyte formed (O), and the condyle remodeled. A connective tissue capsule (short arrows) surrounds the space occupied by the Silastic implant (S). The posterior attachment (PA) and temporal bone (T) are also identified. (207)
insert 2 pictures
Figure 6. Saggital section through the left TMJ of a monkey with a PTIPI without a condylar shave 15 months after placement. A. Teflon (curved arrow) is perforated above the center portion of the condyle (C). Soft-tissue masses (straight arrows) are seen anterior to the condyle, above the Proplast (P), infiltrating the temporal bone (T) posterior to the condyle and next to the ear canal (EC). B. Higher magnification of the anterior soft-tissue mass (M). The mass consists of particles of Proplast and Teflon surrounded by phagocytic cells and a minimal fibrous tissue stroma. The arrows mark two of the larger particles of the implant.

implants needed to be removed over an 8-year period and were found to be fractured. The presence of noise in the remaining patients may indicate fracture of the implant. The group in which the Silastic implants were removed tended to have more pain, noise, and difficulty with chewing than the group in which the implants were maintained. In our evaluation of the patient's perception of the surgical procedure, 83 per cent of the patients with Silastic implants improved, whereas 16 per cent were made worse. Whether this was myofascial pain, joint pain or a combination was not determined.
Wear particles and fragmentation take place when condylar surfaces are functioning against Silastic and Proplast-Teflon. The degree of wear depends on the shape of the condyle and the
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insert 3 pictures
Figure 7.
Diagnosis of failing implants by MRI of the TMJ; ear canal (EC), temporal bone (T), and eminence (E) are seen. A. Normal condylar signal (C) and an intact Silastic implant (arrows) B. Remodelled condyle with an anterior osteophyte (C) and a PTIPI with thinning and wrinkling (arrows). Note the amount of soft tissue surrounding the implanted compared with part A. C. Silastic implant (straight arrows) with a perforation (curved arrow).
load produced by muscle tension and parafunctional habits. Particle formation leads to a foreign-body giant-cell reaction, which may cause breakdown of the bony structures of the joint. The reaction to Proplast-Teflon is more severe and includes damage to the temporal bone with possible perforation into the middle cranial fossa. The body appears to cope better with particles of Silastic by a mechanism not well understood. Particles from both products may cause damage to the joint and its surrounding structures. Particle size or the body's response to the physical structure of the particles may be a factor.
Cervical lymphadenopathy with fragments of the implant in the node tissue can occur. This is more common with silicone, which produces smaller particles more easily transported through the lymphatic system. Tenderness and an increase in the size of the nodes are the only ell effects to date.
Magnetic resonance imaging is the best way to evaluate interpositional implants and the surrounding tissues. Close-follow-up of patients with interpositional implants is necessary to prevent the long-term effects of fragmentation, including lymphadenopathy, bone destruction, occlusal changes and continued chronic pain.
REFERENCES
1. Albert B: Silastic tubing for interpositional arthroplasty J Oral Surg 36:153, 1978
(209)
2.Breckenbaugh RD Dobyns JH Linscheid RL et al: Review and analysis of silicone rubber metacarpo-phalangeal implants J Bone Joint Surg 58(A):483-487,1976
3.Benjamin E. Ahmed H, Rashid ATMF, et al: Silicone lymphadenopathy: A report of two cases, one with concomittant malignant lymphoma. Diagn Histopathol 5: 133-141, 1982
4.Besette RW: Surgical management: Silastic implants. Presented at the Third Annual Meeting on Temporomandibular Joint Pain and Dysfunction. Philadelphia, November 1984.
5.Bronstein SL:Retained alloplastic temporomandibular joint disk implants: A retrospective study. Oral Surg 64:135-145, 1987
6.Calnan J: The use of inert plastic material in reconstructive surgery. BR J Plastic Surg 16:1-22,1963
7.Carter JB:Menisectomy in the Management of Chronic Internal Derangement of the TMJ. Abstracts of the Scientific Sessions, Annual Meeting of the American Association of Oral and Maxillofacial Surgeons 1983.
8.Charnley J: Surgery of the hipjoint: Present and future developments Br Med J 1:821-826, 1960
9.Charnley J, Kamangar A: The optimum size of prosthetic loads in relation to the wear of plastic sockets in total replacement of the hip. Med Bio Engin 7:31-39 1969
10.Christie, Weinberger K. Dietrich M: Silicone lymphadenopathy and synovitis. JAMA 237:1463-1464,1977
11.DeChamplain RW, Gallagher CS Jr., Marchall ET Jr: Autopolymerizing Silastic for interpositional arthroplasty. J Oral Maxillofac Surg 46:522-525 1988
12.Dolwick MF, Aufdemorte TH: SIlicone-induced foreign body reaction and lymphadenopathy after temporomandibular joint arthroplasty. Oral Surg 59:449-458, 1985
13.Dolwick MF, Aufdemorte TB, Cornolius JD: Histopathologic findings to internal temporomandibular joint derangements (abstract 865). Int Assoc Dent Rev. 1984
14.Ekfors TO, ARO II, Maki J, et al: Cystic osteolysis induced by silicone rubber prosthesis. Arch Pathol Lab Med. 108-225-227, 1984
15.Eldeeb M, Holmes RE:Zygomatic and mandibular augmentation with Proplast porous hydroxapatite in rhesus monkeys J Oral Maxillofac Surg 47: 480-488. 1989
16.Estabrooks LN, Murnane TW, Doku HC: The role of condylotomy with interpositional silicone rubber
in temporomandibular joint ankylosis. Oral Surg 34:2-6, 1972
17.Florini BL, Gatto DJ, Wade ML, et al: Tomographic evaluation of temporomandibular joints following discoplasty or placement of polytetrafluoroethylene implants. J Oral Maxillofac Surg 48:183-188, 1988
18.Gallegher DM, Wolford LM: Comparison of Silastic and Proplast implants in the temporomandibular joint after condylectomy for osteoarthritis. J Oral Surg 40: 627-630, 1982
19.Gordon SD: Surgery of the temporomandibular joint, AM I Surg 95:263-266, 1958
20.Grote MA, Ryan DE, Komorowski R et al: Gross anatomy and histology of the temporomandibular joint meniscus in internal derangements (abstract).Proceedings of the Clinical Congress of the American Academy of Oral and Maxillofacial Surgeons, 1984
21.--pramid in arthroplasty of temporomandibular joint in the rabbit. J Oral Surg 28:267-272, 1970
22.Hansen WC,Deshaza BW: Silastic reconstruction of temporomandibular joint meniscus. Plast Reconstr Surg 43:388-391, 1969
23.Hartwell SW Jr, Hall MD: Mandibular condylectomy with silicone rubber replacement. Plast Reconst Surg 53: 440-444-1974
24.Henny FA: Surgical treatment of the painful temporomandibular joint J AM Dent Assoc 79:171-177, 1969
25.Homsy CA, Kent JN, Hinds EC: Materials for oral implantations:Biological and functional criteria J AM Dent Assoc 86:817-832, 1973
26.Homsy CA, Cain TE, Kessler FB et al: Porous implant systems for prosthosis stabilization. Clin Orthop 89: 220-235, 1972
27.Kiersch TA:The use of Proplast implants for meniscoectomy and disk repair in the temporomandicular joint. Abstracts of the Clinical Congress of the American Academy of Oral and Maxillofacial Surgeons, 1984
28.Kneeland JB, Ryan DE, Carrera GF et al: Failed temporomandibular joint prosthesis:MR imaging Radiology 165:179, 1987
29.Lagotteria L, Scapino R., Gransion AS, et al: Patient with lymphadenopathy following temporomandibular joint arthroplasty with Proplast. J. Craniomandib Pract 4:172-178, 1986
30.Leidholt JD, Gorman HA: Teflon hip prostheses in dogs J Bone Joint Surg 47(A):1414-1420,1965
31.Lewis RW, Wright JA: Silastic ulnar head prosthesis for use in surgery of the temporomandibular joint. J Oral Surg 36:906-914, 1978
32.Merrill RC:Survey: TMJ disk removal and interpositional implants. September 11, 1985
33.Merrill RG: Historical perspectives and comparisons of TMJ surgery for internal disc derangements and arthroplasty. J Craniomandib Pract 4:74-85,1986
34.Moriconi RS, Popowich LD, Guernsey IH: Alloplastic reconstruction of the temporomandibular joint. Dent Clin North AM 30:307-325, 1986
35.Murname TW, Doku NC,:Noninterpositional intercapsular arthroplasty of rabbit TMJs J Oral Surg 29:268, 1971
36.Nalbendian R, Swanson AB, Maupin BK: Long term silicone implant arthroplasty: Implications of animal and human autopsy findings. JAMA 250:1195-1198, 1983
37.Palmer D, Perdersen GW: Arthroplasty for bilateral temporomandibular joint ankylosis: Report of case J Oral Surg 30:816-820, 1972
38.Pillegrini V, Burton R: Surgical management of basal joint arthritis of the thumb J Hand Surg 11 (A)39: 309-324, 1986
39.Ryan DE: Menisectomy with Silastic Implants. Abstracts of the Clinical Congress of the American Association of Oral and Maxillofacial Surgeons 1984
40.Sanders B: Surgical Treatment of the TMJ. Abstracts of the Clinical Congress of the American Association of Oral and Maxillofacial Surgeons, 1981
41.Sanders B: Arthroscopic surgery of the temporomandibular joint: Treatment of internal derangement with persistent closed lock Oral Surg 62:361, 1986
42.Schilero J: The implications of silicone implant surgery, J Foot Surg 23: 66-69, 1984
43.Silagi J, Schow C: Temporomandibular joint arthroplasty:Review of the literature of case J Oral Surg 28:920-926, 1970
(210) 44 silicone implants in hand surgery. Hand 15(1)-47-52, 1983
45.Swanson AB:Fingerjoint replacement by silicone rubber implants and the concept of implant fixation by encapsulation. Ann Rheum Dis 28 (suppl), 47-55, 1969
46.Swanson AB:Flexible implant arthroplasty for arthritic finger joints J Bone Joint Surg 54(A):435-455,1973
47.Swanson AB,Swanson GD, Maupin BK:Flexible implant arthroplasty of the radiocarpal joint. Clin Orthoop Rel Res 187:94-106, 1984
48.Takemure R, Zena W:Secretary products of macrophages and their physiological functions. AM J Physiol 246:C1-C9, 1984
49. Timmis DP, Aragon SB, Van Sickels JE, etal: A comparative study of alloplastic replacements in rabbits. Case reports and Outlines of Scientific Sessions, 67th Annual Meeting, American Association of Oral and Maxillofacial Surgeons,1985, p 40
50.Vitek, Inc. Presentation to the Food and Drug Administration Dental Advisory Panel, Washington, DC, 1989
51.Wukelick S, Marshall J, Welden R, et al: Use of a Silastic testicular implant in reconstruction of the temporomandibular joint of a 5 yr old child. Oral Surg 32:4-9,1971
Doran E. Ryan, DDS
Milwaukee County Medical Complex
Oral Surgery Department (Box 107)
8700 West Wisconsin Avenue
Milwaukee, WI 53226
(211)

Disorders of the TMJ II:Arthrotomy 1042-3699/89 $0.00 +.20
Pathology of Alloplastic
Interpositional Implants in the
Temporomandibular Joint

Wei Yung Yih, DDS, MS,*
and Ralph G. Merrill, DDS, MScDt
Prior to arthroscopy, the surgical management of internal derangement of the temporomandibular joint (TMJ) involved disk repair or disk removal either without replacement or with replacement by either alloplastic implants or autogenous tissue. The insertion of biologically acceptable alloplastic material into the TMJ has had the objectives of promoting resurfacing and preventing adhesions between the and fossa, articular degeneration, crepitus, and pain. Two of the most widely used materials are Silastic sheeting and a laminate of Proplast with nonporous Teflon. Proplast is used permanently, whereas silicone rubber has been used both permanently and temporarily. Initial reports of Silastic and Proplast implants in joints experimentally and clinically indicated that these materials were successful, but numerous articles since then have demonstrated the destructive effects of both materials in the form of reactive synovitis, destructive arthritis, lymphadenopathy, and foreign-body granulomatous reactions. These TMJ reactions can cause severe loss of bony structure and open bite deformity.
Despite the discouraging results of implantation of these materials in the TMJ, reports of clinically successful cases appeared periodically in the literature. 13,41,45
The purposes of this presentations are; (1) to give additional evidence of the destructive potential of these implants; (2) to show that the damage is not short term but lasts far beyond the removal of the rejected implants; (3) to illustrate the destructive effects of these implants on subsequent tissue grafts; and (4) to give practitioners insight into the removal of symptomatic implants even though they appear intact at the time of surgery.
LITERATURE REVIEW
Silicone elastomers have been extensively studied and utilized clinically as implants for a wide range of purposes in various anatomic locations. 21,41,53,64 Swanson in 1969 introduced silicone rubber to replace finger joints.64 The use of silicone to restore function and to relieve pain in joints damaged by disease or trauma expanded greatly in the 1970s,65 and the material has been used for reconstruction or repair of wrist, elbow, shoulder, and metatarsal joints and for lower extremity amputation stumps as well as for reconstruction of the TMJ meniscus.25,67
Initially, experimental evaluation by many investigators showed that Silastic implants in block, sheet, or tubular form become surrounded by a fibrous capsule. This encapsulation process occurs without evidence of significant inflammatory or foreign-body reaction except for the occasional finding of intracellular particles of silicone elastomer in macrophages . 36,37,53,57 It was thought that solid sili-
______________________________________________________________________ *Associate Professor, Department of Oral Pathology and Oral and Maxillofacial Surgery, Oregon Health Science University, Portland Oregon
tProfessor and Chairman, Department of Oral and Maxillofacial Surgery, Oregon Health Sciences University, Portland, Oregon

Oral and Maxillofacial Surgery Clinics of North America-Vol 1, No. 2, December 1989
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cone fulfilled many of the requirements of an ideal implant material. 16
Silicone implants are also common in the practice of oral and maxillofacial surgery. In 1981, after presentation of a paper by Sanders, 61 silicone rubber replacement after TMJ diskectomy became popular. 5,32,58 However, reports demonstrate severe reactive synovitis and a foreign-body giant-cell reaction around silicone elastomer particles, occasionally resulting in destructive arthritis. 1,9,11,18,23,60,63,66
In an attempt to duplicate the clinical phenomenon of a foreign-body synovitis from particulate silicone elastomer, Worsing and associates 71 introduced finely ground particulate silicone elastomer into the knee joints of adult New Zealand white rabbits. Histologic evidence of inflammatory changes developed in the synovial tissue similar to those seen in patients. Timmis and coworkers68 used alloplastic materials for TMJ disk replacement in rabbits and found that 21.4 per cent of the Silastic implants were torn. The fragmentation of the implant uniformly observed in the rabbits may have stimulated the marked foreign-body giant-cell reaction.
Eriksson and Westesson17 used Dacron-reinforced silicone material as temporary disk-replacement implants in 27 patients who underwent diskectomy. They found at the time of removal of the implant (1 to 19 months postoperatively) that all but one of the implants showed wear facets and 15 implants were cracked or perforated. Dolwick and Aufdemorte12 studied eight patients who had silicone implants, finding that all tissue specimens revealed granulomatous inflammation and multinucleated giant cells associated with fragmented silicone material. Six of the twenty patients in the series of Westesson and associates70 who had received temporary silicone implants had destructive lesions of the mandibular condyles. A complication of lymphadenopathy resulting from a silicone elastomer finger joint prosthesis has been reported. 9,22,48 Silicone-related lymphadenopathy in the parotid gland resulting from TMJ silicone prostheses was reported by Dolwick and Aufdemorte.12 In 1972, Swanson65 estimated that approximately 1 per cent of prostheses ultimately fracture. However, accumulating experience indicates that as many as 25 per cent of these implants will develop fractures, with potential release of silicone particles and resultant foreign-body reactions.22
Conflicting results were recently reported by Kalamch and coworkers.41 They studied 68 patients who had intra-articular TMJ arthroplasty with Silastic implants. The longest follow-up period was 14 years, 7 months. Sixty-three of the patients had satisfactory results.
More recently, Proplast has been introduced as an implant for correcting various tissue defects. A laminate of Proplast (Vitek, Inc., Dallas, Texas) is a porous form of polytetrafluoroethylene (PTFE) with an admixture of fibers of either vitreous carbon (PTFE C or Proplast I) or aluminum oxide (PTFE-AL2O3 or Proplast II) and Teflon (E. I. Dupont Co., Wilmington, Delaware), a dense smooth form of PTFE. It has a high melting point (above 250 Deg C) and unusual toughness; is insoluble in all common solvents, resistant to chemical attack and anti-frictional; and has a modulus of elasticity resembling that of bone or fibrous tissue.28,33,69 A number of investigators consider that porous PTFE offers more stability than nonporous silicone polymers and hence is more useful clinically. 2,24,27,28 The desirable qualities of Proplast include freedom from adverse reactions, 19, 57 toxicologic safety, 38,57 rapid tissue ingrowth, 2,39,44,57 and biocompatibility. 15,19,38,44,57
Proplast has been studied in a number of animal trials. Proplast coating on stems of replacements of canine femoral heads achieved good results of stabilization without an inflammatory response. 29,30 Halstead and associates,33 who studied the reaction of human tissue to Proplast-coated femoral stems of Thompson prostheses by electron microscopic examination and electron probe microanalysis, found neither round-cell or polymorphonuclear leukocytic infiltration nor tissue necrosis, although macrophages and giant cells were present.
A 1983 presentation reported a very large series of Proplast implants as having outstanding clinical and tissue acceptance6 (TA Kiersch, as quoted by SL Bronstein, Eighth International Conference on Oral Surgery). A survey of 47 oral surgeons with expertise in TMJ surgery conducted by Merrill in 1985 revealed that 17 favored the Proplast-Teflon implants after diskectomy whereas five favored permanent silicone rubber implants.54 A repetition of this survey in 1987 revealed one using Proplast and four silicone.
As early as 1963, Charnley8 warned that PTFE used as a joint replacement is subject to abrasion, which produces particles that incite an intense foreign-body giant-cell reaction with resultant osseous necrosis or granuloma formation. In corroboration, Leidholt and Gorman51 found a foreign-body giant-cell granuloma associated with PTFE fragments between the
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implant and bone interface, resulting in implant fracture. Jones and Jones40 likewise noted intense foreign-body giant-cell reactions at the PTFE-bone interface, causing necrosis of bone and loosening of the prosthesis. Virtually every tissue into which this material has been implanted has shown some type of foreign-body inflammatory reaction. The implantation of PTFE-C in animal subcutaneous tissue resulted in seroma formation, flap necrosis, fragmentation of the material, and numerous foreign-body giant cells. Granulomatous reaction occurred after periurethral injection of Teflon,52 Teflon implantation into the orbit,3 Proplast vascular grafts and ossicular and laryngeal implants.59 A case of lymphadenopathy following TMJ arthroplasty with Proplast has been reported.50 Significant pathologic changes, such as a destructive foreign-body granulation reaction resulting in avascular necrosis of the mandibular condyle and condylar neck, have occurred in the TMJ with association with Teflon-Proplast.6,24,34,42,43,49,50,62.68.70 However, a survey conducted by Vitek, inc. in 1986, to which 322 surgeons responded, revealed that of a total of 6182 Proplast implants placed during the previous 3 years, 5644 (91 per cent) were considered satisfactory, although criteria for success were not specified (quoted by SL Bronstein, May and October 1986).
Kent and coworkers45 designed a three-layer Proplast glenoid fossa in which the superior layer was Proplast I, the middle layer Teflon-FEP polymer, and the inferior layer Teflon-PTFE polymer reinforced with graphite fiber. The prostheses were placed in 192 joints (127 patients) for TMJ reconstruction. The cumulative success rate at 36 to 48 months was 96.11 per cent.
MATERIAL AND METHODS
Sixteen Silastic implants used as temporary disk replacements were removed at planned intervals (two implants after 1 month, seven after 3 months, six after 4 or more months, and one after 6 months). Adjacent tissues were taken for histologic evaluation. another 30 Silastic implants had replaced TMJ disks for periods ranging from 8 months to 5 years. These implants were removed because of symptomatic joints, and the adjacent tissues were obtained for histologic study. Two dermal grafts, four dura matter graphs, and six pedicled temporalis myofascial flaps had replaced the implants. These joints were reoperated on after 1 year because the patients became symptomatic. Nearby tissue also was removed for investigation.
Twenty-two Proplast implants had been used for TMJ disk replacement. All implants were removed because of symptomatic joints (six after 1 year, eight after 2 years, seven after 3 years, and one after 5 years). Two dermal grafts, three dura matter grafts, and two pedicled temporalis myofascial flaps had replaced the implants. After 1 or more years, these joints were reoperated on because patients became symptomatic, and tissue was removed for histologic study.
RESULTS
Silastic Implants
Short-duration Implants
Grossly, the Silastic implants were intact and were usually surrounded by fibrous tissue. Microscopically, fragmentation of silicone with chronic inflammation, foreign-body, giant-cell reaction, and various degrees of fibrosis were present in the synovium capsule, and surrounding tissue.
Long-duration Implants
Grossly, the integrity of the implants ranged from a roughening of the articular surface to tears and frank perforation. The surrounding tissue exhibited fibrosis anklylosis. The articular surface of both the condyle and the glenoid fossa displayed irregularity or erosion. Microscopically, Silastic particles were dispersed throughout the hyalinized fibrous tissue with chronic inflammation and foreign-body reaction (fig.1). Cartilaginous or osseous transformations or both often were present. In two cases, the Silastic granules were found within the macrophages and giant cells in the preauricular lymph nodes.
Implants Followed by Dermal Graft Placement
Grossly, the dermal grafts blended with fibrous tissue. An irregularity of the articular surface of the condyle and the glenoid fossa was evident. Occasionally, fibrous anklylosis occurred. Microscopically, patchy Silastic foreign-body reactions with chronic inflammations were present. The dermal grafts appeared degenerate, hyalinized, and fibrosed.
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Insert 2 pictures-A & B
Figure 1. Response to long-term presence of Silastic. A. Silastic particles with foreign-body giant cells. B. Polarized Silastic crystalline particles in foreign-body giant cells. (Hematoxylin and eosin stain; original magnification x 400)

Implants Followed by Dura Mater Grafts
Grossly, significant fibrosis and granulation tissue were evident. The dura grafts usually could not be recognized. The articular surfaces of both the glenoid fossa and the condyle appeared irregular with occasional fibrous or osseous ankylosis. Microscopically, Silastic foreign-body granulomas were dispersed throughout the tissue. The dura appeared degenerate, fragmented, or fibrosed, and there was cartilaginous or osseous-transformation or both.
Implants Followed by Pedicled Temporalis Myofascial Flaps
Grossly, mild to moderate fibrosis of the muscle flap was present. Microscopically, foci of Silastic foreign-body granulomas and adjacent muscle fiber degeneration were observed.
Proplast Implants
Grossly, the integrity of the implants ranged from a rough surface to destruction. The implants were often dislocated. Tissue reaction to the implant ranged from significant fibrosis to granulomatous masses. The articular surfaces of the condyle and fossa usually appeared irregular or eroded. Microscopically, the tissue showed scattered Proplast particles with significant giant-cell reaction, chronic inflammatory infiltrate, and fibrosis. (Fig. 2). Cartilaginous or osseous transformations or both were often ev-
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INSERT PICTURE
Figure 2. Proplast foreign-body reaction with chronic inflammation, (Hematoxylin and eosin stain; original magnification x 250)

ident. In one case, Proplast granules were found in the macrophages and giant cells in the preauricular lymph nodes.
Implants Followed by Dermal Graft Placement
Grossly, dermal grafts blended with fibrous and granulation tissues. An irregularity of the condylar articular surface and glenoid fossa was seen. Occasional fibrous ankylosis occurred. Microscopically, marked Proplast foreign-body reaction with chronic inflammation was present. The dermal grafts showed hyalinization, degeneration, and fragmentation. In addition, cartilaginous or osseous transformation often occurred.
Implants Followed by Dura Matter Grafts
Grossly, significant fibrosis and granulomatous masses resulted in fibrous and bony ankylosis. The dura tissue blended with the fibrous tissue. An irregularity of the condylar articular surface and the glenoid fossa was often present. Microscopically, a marked Proplast foreign-body reaction with chronic inflammation resulted in necrosis or fragmentation of dura tissue. In one case, an area of casseous-like necrosis was surrounded by Langerhans' giant cells (Fig. 3).
Implants Followed by Pedicled Temporalis Myofascial Flaps
Grossly, granulation tissue and fibrosis were present. Microscopically, foci of Proplast foreign-body granulomas and adjacent muscle fiber degeneration were observed.
DISCUSSION
Early studies with alloplastic implants indicated that they were biocompatible, and reports showed high clinical success rates in the TMJ.14,25,46,61 Although some degenerative changes in the joints were observed radiographically, it was thought that these were an expected and common result of joint surgery. Histologically, giant-cell reactions were considered an indication of movement of the prostheses rather than a biologic reaction and it was thought that this "micromotion" between bone and "coating" would occur continuously.6
The growing concern is that the changes found in the TMJ in conjunction with the insertion of an intra-articular alloplastic substitution after diskectomy are more severe than those described in previous reports. Surgical re-exploration of TMJs with implant prostheses has been necessary because of recurrent joint pain, swelling, or severe occlusal changes and has shown a physical breakdown of the alloplastic material associated with a foreign-body granulation response. Although the exact cause of the foreign-body reaction is not clear, fragmentation of the implant seems to be significant. The production of polymeric wear particles is an inevitable consequence of the gliding movement in artificial joints with plastic components.4,20 Biologically inert block-form materials induce macrophage migration and a foreign-
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INSERT 2 PICTURES 3 & 4
Figure 3-Casseous necrosis with Proplast foreign-body reaction in a dure mater graft. (Hematoxylin and eosin stain; original magnification x 250)
Figure 4-Giant cells containing both Silastic and Proplast particles in a lymph node. (Hematoxylin and eosin stain; original magnification x 250)

body giant-cell reaction when transformed into small particles as a result of biomechanical wear. 17,71 If the size or amount of particles exceeds the capacity of the lymphatic system to remove them, foreign body granulations tissue will form around the joint cavity. Localized tissue destruction then occurs as a result of macrophage secretions of neutral proteinases, acid hydrolases, and other enzymes.20, 70 Destructive arthritis is possible. The extent of implant damage is variable. All but one of the removed implants in Eriksson's study showed wear facets, and nearly half were perforated or cracked.17 Twenty-one per cent of the silicone implants and 46 per cent of the Proplast implants were torn in the rabbit study by Timmis and associates. 68 More than half the implants were cracked or perforated at the time of planned removal in our study.
The hypothesis of destructive reaction resulting from excessive functionel overloading of the implant cannont explain the fact that a foreign-body giant-cell reaction has been found in the unloading area after an alloplastic material was inserted such as a chin or facial implant. It is possible that foreign-body reactions to alloplastic implants result from an inherent property of the implants, which may be unable to maintain their biomechanical integrity, shedding particles into the tissue the implant contacts.
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Figure 5. Response of dura grafts. A. Survival of dura graft with Silastic foreign-body reaction (Hematoxylin and eosin stain; original magnification x 400). B. Extensive degeneration of same graft (upper right) with Silastic foreign-body reaction (lower left). (Hematoxylin and eosin stain; original magnification x 250)

Neel55 studied the tissue response to three types of synthetic implant material--Gore-Tex (polytetrafluroethylene), Proplast (Teflon-laiminated polytetrafluroethylene carbon), and porous polyethylene--in New Zealand white rabbits. Recipient sites for the implants were the perichondral space of the pinna, the subcutaneous tissue of the face, and the paraspinal region. Gore-Tex seemed to be better than Proplast. Gore-Tex is biocompatible in that histiocytes and foreign-body giant-cell reaction in the surrounding tissues were minimal, whereas a profusion of these cells were seen around the Proplast. Moreover, Gore-Tex retained its structure integrity. This study demonstrated that under the same experimental condition, the biomechanical or biochemical characters of implants will greatly influence host tissue reactions.
Excessive functional overloading probably is an important cofactor that will enhance particulate formation by implants. An implant must be completely encapsulated by connective tissue if it is to be successful, probably because encapsulated implants will be isolated from the rest of the host tissue, restricting the destructive reaction to that area.
Dolwick and colleagues12 have described cell-mediated immunity to the inciting agent present in a foreign-body reaction. Granulomatous inflammation with foreign-body giant cells usually originates as an immune reaction to an offending agent that is nondegradable or difficult to process and destroy. Timmis and colleagues68 have also considered that silicone microparticles may act as a hapten-like substance, adsorbing tissue or plasma proteins to form an antigen complex. Granulomatous in-
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INSERT 3 PICTURES-Figures 6A, 6B & 7
Figure 6. Responses of dermal grafts. A. Survival of dermal graft containing sweat glad and its duct. B. Silastic foreign-body reaction with chronic inflammation in same graft, which shows extensive hyalinization. (Hematoxylin and eosin stain; original magnification x 250)
Figure 7. Proplast foreign-body reaction in a dermal graft. (Hematoxylin and eosin stain; original magnification x 250)
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INSERT 2 PICTURES-Figures 8A & 8B

Figure 8. Responses of temporalis muscle flaps. A. Survival of temporalis flap consisting of skeletal muscle bundles with interstitial nerve fibers and adipose tissue.
B. Same flap showing extensive degeneration with Proplast foreign-body reaction and chronic inflammation. (Hematoxylin and eosin stain; original magnification x 250)

flammation will thus be decreased when the fibrous connective tissue grows into the implant. However, in a long-term implant, the histologic constitution of the foreign-body reaction is mainly macrophages and multinucleated giant cells around the particles of implant in the fibrotic stroma. The lack of lymphocytes with the same inciting agent is difficult to reconcile with a specific cell-mediated immunity.
Silicone cytotoxicity may have contributed to the exuberant response seen in the peri-implant tissue.68 Testing using cell cultures has documented the cytotoxic effects of these materials.7 A predominant phenomenon is the inevitable fibrosis in the surrounding tissue. This process is possibly related to the cytotoxicity of the implant. 36,37 This reaction has been used by practitioners with temporary Silastic implants to keep joint recesses open and to stimulate a covering of articular bone. Timmis68 and Eriksson17 and their coworkers have shown that particles of implant are present in the surrounding tissue as early as 1 month postoperatively with an accompanying giant-cell reaction. The peak of the foreign-body reaction to implant particles seems to be around 3 to 4 months. The tissue response will persist for years as the implant continues to shed particles.
The giant-cell response has been reported to extend into bone, muscle, adipose tissue, and even lymph nodes. 31 Lymph node involvement by implant particles is seen not only adjacent to the joint but also at a distance. 9,22,48,50 In our series, two cases of preauricular lymphnode involvement were seen. One followed a
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Silastic implant in the ipsilateral TMJ. The other showed both Proplast and silicone particles in macrophages in the lymph nodes following both implants in the ipsilateral TMJ (Fig. 4). These widely dispersed microscopic and macroscopic granulomatous responses are very difficult to remove totally from the joint and adjacent tissue and may be part of the reason for the many repeat failures after surgical removal of the implant. Numerous articles have emphasized the destructive nature of foreign-body reactions to interpositional implants, but no comments have been made about the influence of residual implant material after the implant has been removed. This study has presented cases in which residual material has persisted and contributed to the demise of subsequent biologic grafts as long as 5 years after the removal of the original alloplastic implant.
We abandoned alloplastic interpositional implants in 1985 and have used several autografts and allografts to repair the damage caused by the alloplastic foreign-body reaction. Dermis had been used in 1985 and afterward. Lyophilized dura mater was used for a short time in 1986 than abandoned because of findings of foreign-body reaction and arthrofibrosis and the possibility of disease transmission. Pedicled temporalis muscle flaps have also been employed. Both dermis and dura matter showed partial or complete degeneration, necrosis, and persistent residual foreign-body reaction (Figs. 5 through 7). Only the pedicled temporalis muscle fascial flap has shown resistance to foreign-body reaction. However, even this graft has exhibited progressive muscle degeneration (Fig. 8).
Cartilage and bone formation were relatively common findings in addition to the ingrowth of fibrous tissue. Diminishing vascularity associated with tissue fibrosis will decrease local oxygen tension. The fibrous tissue will transform into chondroid or osseous tissue or both.35 Chronic inflammation and foreign-body reaction in addition to surgical trauma in the joint with an implant promote the process of fibrosis. That reaction may be responsible for subsequent fibrous or osseous ankylosis of the joint.
The foreign-body reaction associated with PTFE in the TMJ caused more severe osseous erosions of both the mandibular condyle and the glenoid fossa than that of Silastic implants.43 In two cases reported by Schellhas and associates, 62 granulation tissue had eroded through the temporal bone to the dura of the middle cranial fossa. Five of our PTFE implant cases presented a similar severity of complications.
It is now becoming increasingly obvious that a diagnosis of destructive foreign-body reaction should be made as early as possible in order to minimize morbidity. The results of this and other studies have demonstrated that both silicone rubber and the Teflon-Proplast are not biologically acceptable implant materials in the functional TMJ.
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page 221 cont'd
REFERENCES
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2. Arem AJ, Rasmusen D, Maddren W: Soft tissue response to Proplast: Quantitation of scar ingrowth. Plast Reconstr Surg 61:214, 1978
3. Aronowitz JA, Bormely SF, Suma M: Long term stability of Teflon orbital implants. Plast Reconst Surg 79:166, 1986
4. Buchhorn GH, Willert HG: Effects of plastic wear particles on tissue. In Williams DF (ed): Biocompatibility of Orthopedic Implants. Boca Raton, FL, CRC Press, 1982, pp225-257
5. Bessette RW, Katzberg R, Natiella JR, et al: Diagnosis and reconstruction of the human temporomandibular joint after trauma or internal derangement. Plast Reconstr Surg 75:192, 1985
6. Bronstein SL: Retained alloplastic temporomandibular joint disc implants: A retrospective study. Oral Surg Oral Med Oral Pathol 64:135, 1987
7. Chawla AS: Toxicity evaluation of a novel filler free silicone rubber biomaterial by cell culture techniques. J Biomed Mater Res 16:501, 1962
8. Charnley J: Tissue reactions to polytetrafluoroethylene Lancet 2:1379,1963
9. Christie AJ, Weinberger KA, Dietrich M: Silicone lymphadenopathy and synovitis: Complications of silicone elastomer finger joint prostheses. JAMA 237:1463, 1977
10. Christie AJ, Weinbergr KA, Dietrich M: Complications of silicone elastomer prostheses [letter]. JAMA 238:939, 1977
11. Davis PKB, Jones SM: The complications of Silastic implant experiences with 137 consecutive cases. Br J Plast Surg 24: 405, 1971
12. Dolwick MF, Aufdemorte TB: Silicone induced foreign body reaction and lymphadenopathy after temporomandibular joint arthroplasty. Oral Surg Oral Med Oral Pathol 59: 449, 1985
13. Dechamplain RW. Gallagher CS, Marshall ET: Autopolymerizing Silastic for interpositional arthroplasty. J Oral Maxillofac Surg 46:522, 1988
14. Estabrooks LN, Murnare TW, Doku HC: The role of condylotomy with interpositional silicone rubber in temporomandibular joint ankylosis. Oral Surg Oral Med Oral Pathol 34:2, 1972
15. Epstein LI: Clinical experiences with Proplast as an implant. Plast Reconstr Surg 63:219, 1979
16. Eiken O. Lindstrom C, Jonsson K: Silicone carpal implants: Risk or benefit? Scand J Plast Reconst Surg 19: 295, 1985
17. Eriksson L. Westersson P-L: Deterioration of temporary
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silicone implant in the temporomandibular joint: A clinical and arthroscopic follow-up study. Oral Surg Oral Med Oral Pathol 62:2, 1986
18. Ferlic DC, Clayton ML, Holloway M: Complications of silicone implant surgery in the metacarpophalangeal joint. J Bone Joint Surg 57 [A]:991, 1975
19. Freeman BC: Proplast: A porous implant for contour restoration. Br J Plast Surg 29:158, 1976
20. Florine BL, Gatto Dj, Wade M, et al: Tomographic evaluation of temporomandibular joints following discoplasty or placement of polytetrafluoroethylene implants. J Oral Maxillofac Surg 48: 183, 1988
21. Gayou R, Rudolph R: Capsular contraction around silicone mammary prosthesis. Ann Plast Surg 2:62, 1979
22. Groff GD, Schned Ar, Tayer TH: Silicone induced adenopathy eight years after metacapophalangeal arthroplasty. Arthritis Rheum 24:1578, 1981
23. Gordon M, Bullough PG: Synovial and osseous in inflammation in failed silicone rubber prostheses: A reportof six cases. J Bone Joint Surg 64[A]:574, 1982
24. Gallagher DM: Wolford LM: Comparison of Silastic and Proplast implants in the temporomandibular joint after condylectomy for osteoarthritis. J Oral Maxillofac Surg 40:627, 1982
25. Hansen WC, Deshaza BW: Silastic reconstruction of temporomandibular joint meniscus. Plast Reconst Surg 43: 388, 1969
26. Habbi I, Murnane TW, Doku HC: Silastic and Supramid in arthroplasty of the temporomandibular joint in the rabbit. J Oral Surg 28: 267, 1970
27. Homsy CA: Biocompatibility in selection of materials for implantation. J Biomed Mater Res 4:341, 1970
28. Homsy CA: Implant stabilization: Chemical and biochemical considerations. Orthop Clin North Am 4:295, 1973
29. Homsy CA, Kent JN, Hinds EC: Materials for oral implantation: Biological and functional criteria. J Am Dent Assoc 86:817, 1973
30. Homsy CA, Cain TE, Kessler FB, et al: Porous implant systems for prosthesis stabilization. Clin Orthop 89:220, 1972
31. Hausner RJ, Schoen FJ, Pierson KK: Foreign body reaction to silicone gel in axillary lymph nodes after an augmentation mammoplasty. Plast Reconst Surg 62:
381, 1978
32. Hall, HD: Meniscectomy for damaged discs of the temporomandibular joint. South Med J 78: 569, 1985
33. Halstead A, Jones CW, Rawlings RD: A study of the reaction of human tissue to Proplast. J Biomed Mater Res 13:121, 1979
34. Heffez L, Mafee MF, Rosenberg H, et al: CT evaluation of TMJ disc replacement with Proplast-Teflon laminate. J Oral Maxilofac Surg 45: 657, 1987
35. Hall BK: Cartilage. Biomedical Aspects, vol 3. New York, Academic Press, 1988 pp 322-323
36. Imber G, Schwager RG, Guthrie RH, et al: Fibrous capsule formation after sub-cutaneous implantation of synthetic materials in experimental animals. Plast Reconst Surg 54:183, 1974
37. Irving IM, Castilla P, Hall EF, et al: Tissue reaction. to pure and impregnated Silastic. J Pediatr Surg 6:724, 1971
38. Jancke JB, Komorn RM, Cohn AM: Proplast in cavity obliteration and soft tissue augmentation. Arch Otolaryngol 100:24, 1974
39. Jancke JB, Shea JJ: Self-stabilizing Proplast total ossecular replacement prostheses in tympanoplasty. Laryngoscope 85:1550, 1975
40. Jones W, Jones D: The tissue response to Proplast coated Thompson prosthesis and the development of a femoral stem design for use with porous coatings. Proc R Coll Surg 61:381, 1979
41. Kalamch S, Walker RV: Silastic implant as a part of temporomandibular joint arthroplasty: Evaluation of its efficacy. Br J Oral Maxillofac Surg 25: 222, 1987
42. Kaplan PA, Ruskin JD, Tu HK, et al: Erosive arthritis of the tempormandibular joint caused by Teflon-Proplast implants: Plain film features. AJR 151: 337, 1988
43. Katzberg RW, Laskin DM: Radiographic and clinical significance of temporomandibular joint alloplastic disc implants. AJR 151: 736, 1988
44. Kent JN, Homsy CA, Hinds Ec: Proplast in dental facial reconstuction. Oral Surg Oral Med Oral Pathol 38:512, 1974
45. Kent JN, Bloch MS, Homsy, et al: Experience with a polymer glenoid fossa prosthesis for partial or total temporomandibular joint reconstruction. J Oral Maxillofac Surg 48:520, 1986
46. Kent JN, Misiek DJ, Akin Rk, et al: Temporomandibular condylar prostheses: A ten year report. J Oral Maxillofac Surg 41: 245, 1983
47. Kessler FB, Homsy CA, Berkeley ME, et al: Obliteration of traumatically induced articular surface defects using porous implant. J Hand Surg 5:328, 1980
48. Kich T; Silicone lymphadenopathy. Hum Pathol 11:240, 1980
49. Knelland JB, Ryan DE, Carrera G, et al: Failed temporomandibular joint prosthesis: MR imaging.Radiology 165:179,1987
50. Lagrotteria L, Scapino R, Granston AS, et al: Patient with lymphadenopathy following temporomandibular joint arthroplasty with Proplast. J Craniomandib Prac 4: 172, 1986
51. Leidholt JD, Gorman HA: Teflon hip proosthesis in dogs. J Bone Joint Surg 47[A]:1414, 1965
52. Malizia AA, Perman HM. Myers RP, et al: Migration and granulomatous reaction after periurethral injection of polytef (teflon). JAMA 251:3277, 1984
53. Marzoni FA, Upchurch SE, Lambert CJ: An expermental study of silicone as a soft tissue substitute. Plast Reconst Surg 24: 600, 1959
54. Merrill RG: A survey of preferred implant after TMJ diskectomy. Presented at Western Society of Oral and Maxillofacial Surgeons Annual Meeting, Lake Tahoe, June 1986
55. Neal HB: Implants of Gore-Tex: Comparisons of Teflon-coated polytetrafluoroethylene carbon and porous polyethylene implants. Arch Otolaryngol 19:427, 1983
56. Parkers ML, Kamee FM, Merrin ML: Proplast chin augmentation. Laryngoscope 86:1829,1976
57. Rhinelander FW, Stewert CL, Wilson JW, et al: Growth of tissue into a porous low modulus coating on intra-medullary nails, Clin Orthop Apr 1982, 293
58. Rippert ET, Flanigan TJ, Middlebrooks ML: New design for Silastic implants in temporomandibular joint surgery. J Oral Maxillofac Surg 44: 163, 1986
59. Rooney TP, Haug RH, Toor AH, et al: Rapid condylar degeneration after glenoid fossa prosthesis insertion: Report of three cases. J Oral Maxillofac Surg 46:240,1988
60. Rosenthal DI, Rosenberg, AE, Schiller AI, et al: Destructive arthritis due to silicone: A foreign body reaction. Radiology 149:69, 1983
61. Sanders B, Brady Fa, Adams D: Silastic cap tempo-
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romandibular joint prostheses. J Oral Surg 35:933, 1977
62. Schellhas KP, Wilkes CH, El-Deeb M, et al: Permanent Proplast temporomandibular joint implants: MR imaging of destructive complication. AJR 151:731, 1988
63. Smith RJ, Atkinson RE, Jupiter JR: Silicone synovitis of the wrist. J Hand Surg
10A:47, 1985
64. Swanson AB: Finger joint replacement by silicone rubber implants and its concept of implant fixation by encapsulation. Ann Rheum Dis 28(suppl):47, 1969
65. Swanson AB: Flexible implant arthroplasty for arthritic finger joints. J Bone Joint Surg 54[A]: 435:, 1972
66. Swanson AB: Complications of silicone elastomer prostheses [letter]. JAMA 238:939, 1977
67. Swanson AB, Meester WD, Swanson G, et al: Durability of silcone implants: An in vivo study, Orthop Clin North Am:1097, 1973
68. Timmis DP, Aragon SB, Van Sickels J, et al: Comparitive study of alloplastic materials for tempormandibular joint disc replacment in rabbits. J Oral Maxillofac Surg 44:541, 1986
69. Vistnes LM, Ksander GA, Kosek J: Study of encapsulation of silicone rubber implants in animals: A foreign body reaction. Plast Reconstr Surg 62:580, 1978
70. Westesson P-L, Eriksson L, Lindstrom C: Destructive lesions of the mandibular condyle following discectomy with temporary silicone implant. Oral Surg Oral Med Oral Pathol 63:143, 1987
71. Worsing RA, Engber WD, Lange TA: Reactive synovitis from particulate Silastic; J Bone Joint Surg 4:581.1982
Department of Oral and Maxillofacial Surgery
Oregon Health Sciences University
611 Southwest Campus Drive
Portland, Oregon 97201-3097
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APPENDIX 3. --FDA WARNING LETERS TO MANUFACTURERS OF JAW IMPLANTS AND FDA SAFETY ALERT TO DENTISTS
JUN 12 1992

WARNING LETTER

CERTIFIED MAIL-
RETURN RECEIPT REQUESTED

Dr. Andrew Tose President
CeraMed Corporation
12860 West Cedar Drive
Lakewood, Colorado 80228

Re: PermaRidge Alveolar Ridge
Hydroxylapatite Matrix
Dear Mr. Tose:
It has come to our attention that CeraMed Corporation has not been promoting and commercially distributing PermaRidge and OsteoGraf/AR Alveolar Ridge Hydroxylapatite Implants. These products are devices as the term is defined in Section 201(h) of the Federal Food, Drug, and Cosmetic Act (the Act).
Your firm has not submitted a premarket notification for the above products, as required by Section 510(k) of the Act. Failure to submit a premarket notification at least 90 days prior to the intent to market a device in interstate commerce is a prohibited act under Section 301(p) of the Act, and results in the device being misbranded within the meaning of the Section 502(o) of the Act.
Should your Alveolar Ridge Hydroxylapatite implant devices be found to be not substantially equivalent to existing class I or class II devices, then they are classified by statute in class III, requiring an application for premarket approval (PMA) to support the safety and efficacy of the devices. Failure to submit a PMA application prior to marketing a class III device adulterates the devices under Section 501(f)(1)(B) of the Act.
Continued distribution of these devices may result in the misbranding and/or adulteration of the devices, which may result in regulatory actions without further notice. These actions include, but are not limited to seizure, injunction, or civil penalties.
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You should notify this ofice in writing within fifteen (15) working days of your receipt of this letter of the sepcific steps you have taken to correct these violations, including an explantation of each step being taken to preven the recurrance of similar violations. If corrective action cannot be completed with fifteen (15) working days, state the reason for the delay and the time within which the correction will be completed. A copy of this letter has been provided to the Denver District Office. We request that the action being taken to remove the products from the market also be reported to them.
Your response to this letter should be sent to FDA, Center for Devices and Radiological Health, Regulatory Guidance Branch (HFZ-323), 1390 Piccard Drive, Rockville, Maryland 20850, to the attention of Mr. Eric Latish
Sincerely yours,
Ronald M. Johnson
Director
Office of Compliance and Surveillance
Center for Devices and
Radiological Health
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STAMPED MAY 29, 1992

WARNING LETTER

CERTIFIED MAIL-
RETURN RECEIPT REQUESTED

Douglas Morgan, D.D.S. President
TMJ Research Foundation
3043 Foothill, Suite #8
La Cresenta, California 91214

Re: TMJ Implants for Partial or
Total Joint Prostheses

Dear Dr. Morgan:
It has come to our attention that you have been promoting and commercially distributing temporomandibular joint (TMJ) implants intended as partial or total joint prostheses. These products are medical devices as that term is defined by Section 201(h) of the Federal Food, Drug, and Cosmetic Act (the Act).
Your firm has not submitted a premarket notification for the above products, as required by Section 510(k) of the Act. Failure to submit a premarket notification at least 90 days prior to one the intent to ,arket a device in interstate commerce is a prohibited act under Section 301(p) of the Act, and results in the device being misbranded. within the meaning of the Section 502(o) of the Act. Additionally, your firm has not submitted an establishment registration nor listed any devices with the FDA, as required by 21 CFR Part 807. Failure to do this also misbrands your device within the meaning of Section 502(o).
Should your TMJ devices be found to be not substantially equivalent to existing class I or class II devices, then they are classified by statute in class III, requiring an application for premarket approval (PMA) to support the safety and efficacy of the device. Failure to submit a PMA application prior to marketing a class III device, adulterates your device under Section 501(f)(1)(8) of the Act.
Continued distribution of these devices may result in the misbranding and/or adulteration of the devices, which may result in regulatory actions without further notice. These actions include, but are not limited to seizure, injunction, or civil penalties.
You should notify this office in writing within fifteen (15) working days of your receipt of this letter of the specific steps you have
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taken to correct these violations, including an explanation of each step being taken to prevent the recurrence of similar violations. If corrective action cannot be completed within fifteen (15) working days state the reason for delay and the time within which the correction will be completed. A copy of this letter has been provided to the Los Angeles District Office. We request that actin being taken to remove the products from the market also be reported to them.
Your response to this letter should be sent to FDA, Center for Devices and Radiological Health, Regulatory Guidance Branch, (HFZ-323), 1390 Piccard Drive, Rockville, Maryland 20850, to the attention of Mr. Eric Latish.

Sincerely yours,
unsigned
Ronald P. Johnson
Director
Office of Compliance and Surveillance
Center for Devices and Radiological Health
(227)
STAMPED May 29, 1992
CERTIFIED MAIL
RETURN RECEIPT REQUESTED

Mr. Richard A. Buss President
Osteomed Corporation
6062 San Fernando Road
Glendale, California 91202

Re: TMJ Implants for Partial or Total
Joint Prostheses
Dear Mr. Buss:
It has come to our attention that Ostomed Corporation has been promoting and commercially distributing temporomandibular joint (TMJ) implants intended as partial or total joint prostheses. These products are medical devices as that term is defined in Section 201 (h) of the Federal, Drug and Cosmetic Act (the Act).
Your firm has not submitted a premarket notification for the above products, as required by Section 510 (k) of the Act. Failure to submit a premarket notification at least 90 days prior to the intent to market a device in interstate commerce is a prohibited act under Section 301(p) of the Act, and results in the device being misbranded within the meaning of Section 502(o) of the Act.
Should your TMJ devices be found to be not substantially equivalent to existing class I or class II devices, then they are classified by statute in class III, requiring an application for premarket approval (PMA) to support the safety and efficacy of the device. Failure to submit a PMA application prior to marketing a class III device, adulterates your device under Section 501(f)(I)(B) of the Act.
Continued distribution of these devices may result in the misbranding and/or adulteration of the devices, which may result in regulatory actions without further notice. These actions include, but are not limited to seizure, injunction, or civil penalties.
You should notify this office within (15) working days of your receipt of this letter of the specific steps you have taken to correct these violations, including an explanation if each step being taken to prevent the recurrence of similar violations. If corrective action cannot be completed with fifteen (15) working days state the reason for the delay and the time within which the correction will be completed. A copy of this letter has been provided to the Los Angeles District Office. We request that action being taken to remove the products from the market also be reported to them
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Your response to the letter should be sent to FDA, Center for Device and Radiological Health, Regulatory Guidance Branch, (HFZ-323), 1390 Piccard Drive, Rockville, Maryland 20850, to the attention of Mr. Eric Latish.

Sincerely yours,
unsigned
Ronald M. Johnson
Director - Office of Compliance and
Surveillance -Center for Devices and Radiological Health
(229)
STAMPED MAY 29, 1992

WARNING LETTER

CERTIFIED MAIL
RETURN RECEIPT REQUESTED

Mr. Roger Ammann President
Techmedica, Inc.
1380 Flynn Road
Camarillo, California 93012

Re: TMJ Implants for Partial or Total
Joint Prostheses

Dear Mr. Ammann:
It has come to our attention that Techmedica, Incorporated has been promoting and commercially distributing temporomandibular joint (TMJ) implants intended as partial or total joint prostheses. These products are medical devices as that term is defined in Section 201 (h) of the Federal Food, Drug, and Cosmetic Act (the Act).
Your firm has not submitted a premarket notification for the above products, as required by Section 510(k) of the Act. Failure to submit a premarket notification at least 90 days prior to the intent to market a device in interstate commerce is a prohibited act under Section 301(p) of the Act, and results in the device being misbranded within the meaning of Section 502(o) of the Act.
Should your TMJ devices be found to be not substantially equivalent to existing class I or class II devices, then they are classified by statute in class III, requiring an application for premarket approval (PMA) to support the safety and efficacy of the de-vice. Failure to submit a PMA application prior to marketing a class III device, adulterates your device under Section(f)(1)(B) of the Act.
Continued distribution of these devices, which may result in regulatory actions without further notice. These actions include, but are not limited to, seizure, injunction, or civil penalties.
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You should notify this office in writing within fifteen (15) working days of your receipt of this letter of the specific steps you have taken to correct these violation, including an explanation of each step being taken to prevent the recurrence of similar violations. If corrective action cannot be completed with fifteen (15) working days state the reason for the delay and the time within which the correction will be completed. A copy of this letter has been provided to the Los Angeles District Office. We request that the action being taken to remove the products from the market also be reported to them.
Your response to this letter should be sent to FDA, Center for Devices and Radiological Health, Regulatory Guidance Branch, (HFZ-323), 1390 Piccard Drive, Rockville, Maryland 20850, to the attention of Mr. Eric Latish.

Sincerely yours,
unsigned
Ronald M. Johnson Director
Office of Compliance and Surveillance
Center for Devices and Radiological Health
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stamped May 29, 1992

WARNING LETTER

CERTIFIED MAIL -
RETURN RECEIPT REQUESTED

Ms. Mary P. Morgan President
Timesh Inc.
76 Spectrum Road
Las Vegas, Nevada 89101
Re: TMJ implants for Partial or Total Joint
Prostheses
Dear Ms. Morgan:
It has come to our attention that TiMesh, Incorporated has been promoting and commercially distributing temporomandibular joint (TMJ) implants intended as partial or total joint prostheses. These products are medical devices as that term is defined in Section 201(h) of the Federal Food, Drug, and Cosmetic Act (the Act).
Your firm has not submitted a premarket notification for the above products, as required by Section 510(k) of the Act. Failure to submit a premarket notification at least 90 days prior to the intent to market a device in interstate commerce is a prohibited act under Section 301(p) of the Act, and results in the device being mis-branded within the meaning of Section 502(o) of the Act.
Should your TMJ devices be found to be not substantially equivalent to existing class I or class II devices, then they are classified by statute in class III, requiring an application for premarket approval (PMA) to support the safety and efficacy of the device. Failure to submit a PMA applicant prior to marketing a class III device, adulterates our device under Section 501 (f)(1)(B) of the Act.
Continued distribution of these devices may result in the misbranding and/or adulteration of the devices, which may result in regulatory actions without further notice. These actions include, but are not limited to seizure, injunction, or civil penalties
You should notify this office in writing within fifteen (15) working days of your receipt of this letter of the specific steps you have taken to correct these violations, including an explanation of each step being taken to prevent the recurrence of similar violations. If corrective action cannot be completed within fifteen (15 days) working days
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state the reason for the delay and the time within which the correction will be completed. A copy of this letter has been provided to the San Francisco District Office. We request that the action being taken to remove the products from the market also be reported to them.
Your response to this letter should be sent to FDA, Center for Devices and Radiological Health, Regulatory Guidance Branch. (HFZ-323), 1390 Piccard Drive, Rockville, Maryland 20850, to the attention of Mr. Eric Latish.

Sincerely yours,
unsigned
Ronald M. Johnson Director
Office of Compliance and Surveillance
Center for Devices and Radiological Health
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DEPARTMENT OF HEALTH & HUMAN SERVICES PUBLIC HEALTH SERVICE
Food and Drug Administration
Bldg.20, Denver Federal Center
POBOX 25087
Denver, Colorado 25087
303-236-3000 (FTS:776-3000)
January 27, 1992

CERTIFIED MAIL RETURN RECEIPT REQUESTED

Robert W. Christensen, President
TMJ Implants, Inc.
17301 West Colfax Avenue, STE 275
Golden, Colorado 80401

WARNING LETTER

.
Dear Mr. Christensen:

During an inspection of your firm TMJ Implants, Inc., located at 17301 West Colfax Avenue, STE 275, Golden, Colorado, between December 16, 1991 and January 7, 1992, Investigator Jose R. Hernadez determined that your establishment has failed to provide pre-market notification submissions (Section 510(k) of the Federal Food, Drug, and Cosmetic Act) for certain implantable devices. Our inspection revealed that the manufacturing process was significantly altered by TMJ Imlants, Inc. for the purpose of rendering the device sterile. You were informed by Investigator Hernadez at the time of the inspection that a pre-market submission is required for such a change in the device manufacturing process.
In your January 10, 1992 letter to Mr. Richard Aleman, Director of Investigations, Denver District, you cite page 329 of the HHS Publication, "Sterile Medical Devices: A GMP Workshop Manual" as justification for not having to submit a 510(k) pre-market notification. However, per that document, a manufacturer must have"...provided adequate assurance through change control procedures, ... process validation, personnel training, and development of routine sterilization procedures that those changes could not effect the safety and effectiveness of the device...". Our inspection of your firm revealed that you did not properly validate this change in order to assure that radiation sterilization has not in fact affected the safety and effectiveness of your devices.
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The continued marketing of medical devices without complying with the pre-market notification requirements of Section 510(k) causes the articles to be misbranded under Section 502(o) of the Act. The continued marketing of these devices may result in regulatory action without further notice. These actions include seizure and/or injunction.
Several deviations from the Good Manufacturing Practice, Regulations (title 21, Code of Federal Regulations part 820) were noted during this inspection. Those deviations include:
!. Inadequate quality assurance and audit procedures (21 CFR 820.20(a) & (b));
2.Incomplete device master records (21 CFR 820.181);
3.Inadequate finished device inspection procedures (21 CFR 820.160, and
4.Failure to perform adequate complaint investigations (21 CFR 820.198(b).
The above identification of violations is not intended to be an all-inclusive list of deficiencies at your facility. It is your responsibility to assure adherence with each of the regulations. Until these violations are corrected, Federal agencies will be informed that FDA recommends against the award of contracts for the affected products.
You should notify this office in writing, within 15 working days of receipt of this letter, of the specific steps you have taken to correct the noted violations, including an explanation of each step being taken to prevent the recurrance of similar violations. If corrective action cannot be completed with 15 working days, state the reason for the delay and the time within which the correction will be completed.
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Your reply should be sent to the Food and Drug Administration, Denver District Office, Attention: Regina A. Barrell, Compliance Office at the above address
Sincerely,
signed
John H. Scharmann District Manager
Enclosure: FDA 483
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DEPARTMENT OF HEALTH & HUMAN SERVICES PUBLIC HEALTH SERVICE
Food and Drug Administration
Bldg 20, Denver Federal Center
Post Office Box 25087
Denver Colorado 80225-0087
303-236-3000: FTS: 776-3000
May 27, 1992

Dr. Robert W. Christensen -President
TMJ Implants., Inc.
17301 West Colfax Avenue STE 275
Goldon, Colorado 80401

Dear Dr. Christensen:
This letter is in response to your correspondence dated March 16, 1992 and April 17, 1992, and as a follow-up to our meeting of March 10, 1992. As you will recall during our March 10 meeting, we discussed the need for your firm to have validated the sterilization procedures used on the Fossa and Condylar Prosthesis. We informed you that without such validation data, a premarket notification application (510(k)) was required to be submitted.
The documentation you submitted indicates that you have utilized a bioburden of 4.2 cfu's per device as the challenge for the AAMI B1 dose setting determinations. Examination of the bioburden data shows that some of the individual devices tested, greatly exceeded (five times the average of 4.2) this contamination level. The utilization of 4.2 cfu's and a verification dose of .4 Mrads may not be valid as it appears that your firm has not reliably determined the true bioburden levels present on your device. In order to support your use of these levels, the result of several lots for which bioburden levels were determined would need to be studied.
The package integrity testing performed by your firm is not adequate in validating the sealing operations. Your firm has not documented the sealing equipment operational settings, in order to demonstrate the process, are under control and the settings are traceable to the satisfactory package integrity results submitted. Further, you have failed to submit standard operating procedures that reflect the operational settings for the packaging equipment.
The adequacy of these and other responses made to the FDA 483 list of observations regarding sterilization and/or GMR issues will be determined a the next inspection of your facility. However, we
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have determined that the changes made to your devices are indeed significant ones which do, in fact, require the submissions of a premarket notification application.
Aside from the issue of sterilization, it has come to our attention that at a symposium held in Norristown, New Jersey, March 1992, TMJ Implants advertised that they have made "great improvements" to these implants. These improvements include a change in the articulating surface of the implants, as well a change in the condylar stem geometry in order to increase the size in response to reports of stem fractures. We consider these changes in the devices to be significant, as stated, above, and therefore, requires a 510(k) filing per 21 Code of Federal Regulations, part of 807.81 (a)(3)(i). Per the warning letter dated January 27, 1992, the continued marketing of medical devices without complying with the pre-market-notifiction requirements of section 510(k), causes the articles to be misbranded under Section 502(0) of the Act. Failure to comply with the above requirements may result in such regulatory action as seizure of the devices or injunction without further notice.
Sincerely,
signed
Regina A. Barrell - Compliance Office
bcc: HFA 224, HFC 230, HFF 310, HFZ 323, DIB f/u 6-30-92
EI, RF, RAB Chrono
RABarrell, mi 052792
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DEPARTMENT OF HEALTH & HUMAN SERVICES Public Health Service
_________________________________________________________________________________
Food and Drug Administration 1330 Piccard Drive
Rockville MD 20850
stamped May 29, 1992

WARNING LETTER

CERTIFIED MAIL RETURNED RECEIPT REQUESTED

Charles A. Homsy, Sc.D.
President and Chairman of the Board,
Novamed, Inc.
Chairman of the Board,
Oral Surgery Marketing Inc.
3142 Telge St
Houston TX 77054

Dear Dr. Homsy:

After review by our Office of Device Evaluation of your labeling, catalogues and other material obtained during inspections of your companies, we have concluded that Proplast device (including those made in whole or in part of Proplast I, Proplast II, or Proplast HA) are in violation of the Federal Food, Drug, and Cosmetic Act (the Act)
These devices include but are not limited to:

PRODUCT IDENTIFICATION

Otoplasty
Glenoid Fossa VK
Mandibular Condyle VK
Ocular Globe (Proplast II)
Trochanter Pad (Proplast HA)
Staple Cushion Pad (Proplast HA)
Tissue Custom Pad (Proplast HA)
Other Reconstruction Block & Sheeting Material
Preformed Implants
Other Implants, i.e., mandible, forehead, maxilla,
pectus and orbital areas
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These devices are misbranded under Section 502(o) in that you have either failed to file a premarket notification submission as required by Section 510(k) of the Act or these devices have undergone significant changes in labeling or material composition, which warrant the submission of a new premarket notification [510(k)].
Furthermore, we note that labeling for your Proplast products contain claims which have not been included in any previous 510(k)'s. These claims include references which describe the properties of the Proplast material, such as "chemically inert; its porosity promotes stabilization enabling as much of the 80% of implant volume to become tissue without encapsulation, sagging or migration." Labeling also describes Proplast II and HA as being "inert, biocompatable, free from observable systemic or cytotoxic effects, and aids in the migration of cells, and Proplast HA as osteoconductive."
We are not aware of preclinical or clinical evidence to support these claims. Therefore, if you have any information supported by preclinical or Clinical evidence from scientifically valid studies that you wish us to consider you must provide the information in new 510(k) submissions filed in accordance with 21 CFR 807.81, as outlined in the described format in 21 CFR 807.90.
Continued distribution of these devices may result in the misbranding and/or adulteration of the devices, which may result in regulatory action without further notice. These actions include, but are not limited to, seizure, injunction, civil penalties, and/or automatic detention and refusal to permit entry of products offered for entry into the United States.
You should notify this office in writing with fifteen (15) working days of your receipt of this letter of the specific steps you have taken to correct these violations, including an explanation of each step being taken to prevent the recurrence of similar violations. A copy of this letter has been provided to the Dallas District Office. We request that the action being taken to remove these violative products from the market be reported to them.
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Your response to this letter should be sent to:
Mr. Donald Watchko
Case Management Branch, HFZ-322
Center for Devices and Radiological Health
Food and Drug Administration
1390 Piccard Drive
Rockville, MD 20850

Sincerely yours,
signed
William H. Damaska Director
Division of Compliance Operations
Office of Compliance and Surveillance Center for Devices and Radiological Health
cc:Linda Marshall, ESQ.
Alexander & McEvily
5 Past Oak Park 24th Floor
Houston, TX 77027
Dr. Charles A. Homsy
11526 Raintree Circle
Houston TX 77024
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DEPARTMENT OF HEALTH & HUMAN SERVICES Public Health Services
_________________________________________________________________________________ Food and Drug Administration
Rockville MD 20857

FDA SAFETY ALERT
SERIOUS PROBLEMS WITH PROPLAST(r)-COATED TMJ IMPLANT

To Oral and Maxillofacial Surgeons: December 28, 1990

This is to urge you to re-examine all of your patients who have received temporomandibular joint (TMJ) interpositional implants which manufactured or marketed by either Vitek Inc. or Oral Surgery Marketing, Inc. (both of Houston, TX). These implants were distributed between February 1983 and June 1988 and were the subject of Vitek's March 23, 1990 safety alert. The patent for this medical device is currently held by Hadaco, Ltd. (British Virgin Islands). Any remaining implants should not be used and returned to:

Bonham, Carrington, and Fox
Bankruptcy Trustees for Vitek, Inc.

400 One Shell Plaza
Houston, TX 77002
Attention: Mr. Ben Floyd
PROBLEM
These implants, all of which are made of Proplast (R) (Teflone(R) -carbon or Teflon (R)-aluminum oxide fiber composite). have been associated with implant perforation, fragmentation and/or a foreign body response which may result in progressive bone degeneration of the mandibular condyle and/or the glenoid fossa (1-3), If bone degeneration continues unchecked, patients may experience intense pain and severely limited joint function. One study found that all patients with Proplast (R)-coated TMJ interpositional implants who experienced complications demonstrated progressive bone degeneration in as little as one to two years (1). In a second study, implant failure and bone degeneration occurred in both symptomatic and asymptomatic patients (2).
RECOMMENDATIONS
Because asymtomatic patients may experience bone degeneration, FDA recommends that all patients with these implants who have not had a radiograph taken in the past six months undergo immediate and appropriate radiographic examination. The examination will assist in determining if loss of implant integrity has occurred or if progressive bone degeneration occurring
* If loss of implant integrity or progressive bone degeneration is not occurring, regular radiographic examinations of the implant should be performed every six months for as long as it remains in the jaw.
* If either loss of implant integrity or progressive bone degeneration is found, explanation may be appropriate. If explantation is chosen, patients should be evaluated to determine what alternative procedures might be appropriate, e.g., a non Proplast (R) coated implant, an autologeous bone graft, or no replacement (symptomatic management).
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APPENDIX 4.-DOCUMENTS PROVIDED BY MANUFACTURERS ABOUT SAFETY OF THEIR JAW IMPLANTS
DOW CORNING

June 2, 1992

The Honorable Ted Weiss
Chairman, Subcommittee on Human Resources and Intergovernmental Relations
U. S. Government Operations Committee
B-372 Rayburn House Office Building
Washington, D. C. 20515-5148

Dear Chairman Weiss:

Thank you for your letter of May 28th offering Dow Corning the opportunity to provide information for your June 4 subcommittee hearing.
As indicated in the attached product brochure and package insert, Dow Corning developed a temporary implant specifically designed for treating internal derangements in the temporomandibular joint or TMJ. Available since 1985, the Silastic(R) Temporomandibular Joint Implant HP (Wilkes Design) differs from other TMJ implants in the following ways:
- It is a temporary implant which should be removed from one to two months after surgery. This modality was specifically selected to minimize the potential problems occasionally noted with long-term TMJ implants.
- This device is a disc used as a temporary spacer rather than a permanent total joint replacement implant. This approach was selected because it was known in the medical community that a permanent device could have complications in load bearing joints. For additional information, please reference the enclosed paper from the American Association of Oral and Maxillofacial Surgeons.
- The device is fully fabricated from silicone elastomer rather than other materials like carbon fiber or teflon.

Dow Corning's TMJ implant became commercially available in 1985 after receiving FDA 510K approval in 1984. This special purpose implant was specifically designed solely for the treatment of TMJ dysfunctions in accordance with the package insert and is our preferred products for those specific situations.

DOW CORNING CORPORATION, MIDLAND, MICHIGAN 48686-0995
TELEPHONE 517 496-4000
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Dow Corning also provides general purpose silicone sheeting which is sold to distributors for a variety of applications. This material is sometimes used to prevent soft tissue fibrosis or bony ankylosis following surgical corrections of trismus, a condition in which a patient has problems opening his or her jaw, or related TMJ dysfunctions. The attached product data sheet for Silastic Medical Sheeting makes
reference to this application, as well as the many others. It has been known in the medical community that this sheeting is not to be used as a permanent interface in load bearing joints. The attached product data sheet for Silastic(R) HP sheeting clearly recommends that this material not be used as a permanent interface. This additional recommendation was included to ensure physicians would not infer that they could use this newer, more durable form of sheeting as a permanent interface.
In addition to product literature, I am also including the following:
- A summary of our safety research which we developed as a specific response to your request of May 28th.
- 1984 Criteria for TMJ Meniscus Surgery. This paper was developed by the AD Hoc Study Group on TMJ Meniscus surgery, under the auspices of the American Association of Oral and Maxillofacial Surgeons.
In addition to sending this letter information via facsimile, I am arranging to have original copies of our product literature delivered to Dr. Diana Zuckerman of your staff on Tuesday, June 2. An original copy of this letter and the attachments will follow.
If I can be of any more assistance to you, please do not hesitate to contact me.

Very truly yours,
signed
Robert T. Rylee II
Chairman Health Care Business
cc: Diana Zuckerman, Ph.D.
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SYNOPSIS
NON-CLINICAL BIOCOMPATIBILITY STUDIES OF SILICONE ELASTOMERS
USED IN TEMPOROMANDIBULAR JOINT APPLICATIONS

This summary of non-clinical safety studies of silicone elastomers is directed to dimethylsiloxane elastomers, peroxide and platinum-catalyzed, that are relevant to materials used in temporomandibular joint (TMJ) applications. Safety studies of closely related dimethyl elastomers are also included in the non-clinical review.
ACUTE TOXICITY - These silicone elastomers are not toxic with regard to cytotoxicity, U.S.P. Class V, pyrogenicity, skin sensitization, hemolysis or thrombogenicity.
TERATOLOGY/REPRODUCTION - Silicone elastomers are without teratogenic activity nor do they alter normal production.
GENOTOXICITY - Silicone elastomers and elastomer extracts are genetically inactive in the Ames bacterial reverse mutation assay.
IMMUNOLOGY - Platinum system elastomer does not have immunoenhancement or immunosuppression activity in validated animal models.
SUBCHRONIC/CHRONIC TOXICITY - Peroxide and platinum system silicone elastomers all associated with a foreign body reaction characteristic of a broad range of persistent alloplastic materials. That is, an early acute inflammatory response is superseded by a chronic inflammatory phase (i.e., an infiltrate of predominantly macrophages) that transitions to fiboblastic activity and fibrous connective tissue encapsulation of the foreign body. A sparse dispersal of macrophages and giant cells may persist long-term although this is not characteristic of all implantation sites in all animals. This response pattern is the same for both intramuscular and subcutaneous implantation sites.
The results of elastomer implantation studies ranging in duration from a few days to 2 years demonstrate that reinforced silicone elastomers induce no consistent systemic effects on any organ system.
Elastomer samples measuring 0.1 x 1 cm (0.245cm2) and total surface areas up to 2 cm2, per rat do not induce implantation site tumors (solid-state tumorigenisis) nor an excess of tumors remote
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from the implantation site.
ADME - The fumed amorphous siica used as a reinforcing silica maintains a stable distribution within silicone elastomers. In addition, the surface morphology of the elastomer is not influenced by up to 6 month subcutaneous implantation.
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SILICONE ELASTOMERS USED IN TMJ APPLICATIONS
SUMMARY OF BIOCOMPATIBILITY TESTING

Silicone sheeting is known to have been used as an intra-articular spacing material to correct TMJ defects. In addition a fabricated spacer known as the Wilkes design is manufactured by Dow Corning Corporation and distributed by Dow Corning Wright.
Sheeting catalog numbers 500, 501, 502 are polydimethlsiloxane elastomers that are peroxide catalyzed using 2,4-dichlorobenzoyl peroxide. The basic materials in this category include MDF-372 (also known as MDX4-4515) and MDF-373 (also known as MDX4-4516). These peroxide-catalyzed elastomers are compositionally closely related. Safety studies supporting these materials are summarized below. Another elastomer sheeting and the Wilkes design TMJ device are both of the platinum-catalyzed high performance (H.P.) type. Safety data supporting these materials is summarized following the peroxide systems.
PEROXIDE-CATALYZED ELASTOMERS -
These peroxide-catalyzed elastomers encompass a small number of products by material number including MDF-372 (also known as MDX4-4515) and MDF-373 (also known as MDX4-4516).
ACUTE TOXICITY
Acute toxicity testing of peroxide elastomers includes cytotoxicity, U.S.P. Class V, pyrogenicity, sensitization and hemolysis/thrombogenicity testing.
1. IN VITRO CYTOTOXICITY -
Tissue cell culture biocompatibility testing usually employed WI-38 human embryonic lung cells. The tabulated results indicated that peroxide system elastomers are not cytopathic in culture.
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TISSUE CELL CULTURE BIOCOMPATIBILITY

MATERIAL DIRECT CONTACT MATERIAL EXTRACTS __________________________________________________________ MDX4-4515 NCE NCE
MDX4-4516 NCE NCE
___________________________________________________________
*NCE = No Cytopathic effect.
2. U.S.P. CLASS V -
U.S.P. Class V tests have been done for both of the peroxide elastomers.
Each elastomer was tested for systemic toxicity in the mouse and intradermal toxicity in the rabbit using U.S.P. protocols. No adverse effects were seen.
3. PYROGENICITY -
Both peroxide elastomers pass U.S.P. pyrogenicity testing.
4. SENSITIZATION -
Both peroxide elastomers have been tested for skin sensitization in the guinea pig using topical contact and intradermal FCA injected between the insult and challenge applications of silicone gel. There was no evidence of
sensitization for any of the silicone gel formulations.
5. HEMOLYSIS AND THROMBOGENICITY -
MDX4-4515 has been tested directly and as saline extracts for hemolytic
activity using rabbit blood. This elastomer is not hemolytic.
MDX4-4515 has been assayed for thrombogenicity in a closed cell kinetic blood coagulation test using dog blood. This elastomer was found to not be more thrombogenic than a reference elastomer.
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SUBCHRONIC TOXICITY

SUBCHRONIC ELASTOMER IMPLANTATION

GEL SPECIES DOSE DURATION RESULT
MDX4-4515 Rabbit 4: 0.1x1 cm 3,30,90 FBR
I.M. Days
2: 0.1x1 cm 3,30,90 FBR
S.Q. Days

MDX4-4515 Rabbit 4: 0.1x1 cm 30,60,90 FBR
I.M. Days
2: 0.1x1 cm 30,60,90 FBR
S.Q. Days

MDX4-4515 Rabbit 4: 0.1x1 cm 7,28,91 FBR
I.M. Days
2: 0.1x1 cm 7,28,91 FBR
S.Q. Days
MDX4-4515 Rabbit 4: 0.1x1 cm 7,28,91 FBR
I.M. Days
2: 0.1x1 cm 7,28,91 FBR
S.Q. Days
MDX4-4515 Rabbit 4: 0.1x1 cm 7,28,91 FBR
I.M. Days
2: 0.1x1 cm 7,28,91 FBR
S.Q. Days
MDX4-4516 Rabbit 4: 0.1x1 cm 10,30,90 FBR
I.M. Days
2: 0.1x1 cm 10,30,90 FBR
S.Q. Days
______________________________________________________________________
*4 rods I.M. and 2 rods S.Q. per animal.
#FBR = Foreign Body Reaction
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These subchronic studies indicate that peroxide system silicone elastomers are associated with a foreign body reaction characteristic of a broad range of persistent alloplastic materials such as the U.S.P. polyethylene employed as the control materials in these studies. That is, an early acute inflammatory response is superseded by a chronic inflammatory phase (i.e., an infiltrate of predominantly macrophages) that transitions to fibroblastic activity and fibrous connective tissue encapsulation of the foreign body. A sparse dispersal of macrophages and giant cells may persist long-term although this is not characteristic of all implantation sites in all animals. This response pattern is the same for both intramuscular and subcutaneous implantation sites.
CHRONIC TOXICITY
Three chronic peroxide-catalyzed elastomer studies are available as summarized in the following table.

CHRONIC ELASTOMER IMPLANTATION

MATERIAL SPECIES DOSE DURATION RESULT
MDX4-4515 Dog 5 dogs, Wafers, 3 Year FBR#
I.M. & S.Q.
Perforated and
not Perforated
MDX4-4515 Rat ~0.1x1 cm Rod 2 Year NAE**
S.Q.
MDX4-4515 Dog 2 Dogs 10 Year FBR with
Amputation Stumps Particle Degeneration
______________________________________________________________________
# FBR = Foreign Body Reaction
**NAE = No Adverse Effect
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PLATINUM-CATALYZED ELASTOMERS -
These dimethyl elastomers are of the tear resistant high performance type and are classified as system D elastomers; i.e., platinum catalyzed. Safety studies are also available for several other elastomer products that contribute to an understanding of the safety of system D elastomers. The product designations are Q7-2423,Q7-2222,Q7-2383, Q7-2412,Q7-2424, Q7-2566, Q7-2722, Q7-2743, Q7-2744 and MDF-0077 and MDF-0081. All of these elastomers are closely related using the same elastomer base, amorphous silica filler, silicone plasticizer, catalyst, cross-linker and inhibitor in varying ratios to achieve the desired physical properties. In addition, some of these products contain additives such as water, and barium sulfate to impart radiopacity.
ACUTE TOXICITY:
Acute toxicity testing of system D elastomers includes eye/skin/oral, cytotoxicity, U.S.P. Class V, pyrogenicity, sensitization and hemolysis/thrombogenicity testing.
1. IN VITRO CYTOTOXICITY -
Tissue cell culture biocompatibility testing usually employed WI-38 human embryonic lung cells. The tabulated results indicate that system D elastomers are not cytopathic in culture.

TISSUE CELL CULTURE BIOCOMPATIBILITY

MATERIAL DIRECT CONTACT MATERIAL EXTRACTS
Q7-2222 NCE NCE
Q7-2352 NCE NCE
Q7-2412 NCE NCE
Q7-2423 NCE NCE
Q7-2424 NCE NCE
Q7-2566 NCE NCE
Q7-2643 NCE NCE
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Q7-2722 NCE NCE
Q7-2743 NCE NCE
Q7-2744 NCE NCE
MDF-0077 NCE --
MDF-0081 NCE NCE
______________________________________________________________________
*NCE = No Cytopathic effect
2. U.S.P. CLASS V -
U.S.P. Class V test have been done for 11 of the 12 elastomers listed in the preceding table. Each elastomer was tested for systemic toxicity in the mouse and intradermal toxicity in the rabbit using U.S.P. protocols. No ad-
verse effects were seen.
3. PYROGENICITY -
Ten of the 12 system D elastomers have passed U.S.P. pyrogenicity testing.
4. SENSITIZATION -
Ten of the 12 system D elastomers have been tested for skin sensitization in the guinea pig using topical contact and intradermal FCA injected between the insult and the challenge applications of silicone gel. There was no evidence of sensitization for any of the silicone gel formulations.
5. HEMOLYSIS AND THROMBOGENICITY -
Q7-2566, Q7-2643 and Q7-2743 have been tested directly and as saline extracts for hemolytic activity using rabbit blood. Neither elastomer was
found to induce hemolysis.
Q7-2383, Q7-2424, Q7-2566 and Q7-2643 have been assayed for
thrombogenicity in a closed cell kinetic blood coagulation test using dog
blood. These elastomers were found to not be
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more thrombogenic than a reference elastomer.
TERATOLOGY/REPRODUCTION:
Elastomer Q7-2423/Q7-2551 was tested for a teratogenic potential in the rabbit. U.P.S. polyethylene and viscous solution of carboxymethycellulose served as the
control material. All materials were implanted subcutaneously 6 weeks prior to in-semination in groups of 25 rabbits. There were no significant treatment-related effects on adult female appearance, behavior, body weight change or necropsy findings for the silicone elastomer group. No developmental effects including teratogenicity were observed in the litters in the treatment group implanted with Q&-2423/Q7-2551.
Elastomer Q7-2159A/Q7-2551 has been the subject of study regarding reproductive effects and teratogenicity in a one-generation rat study. No adverse effects were reported.
GENOTOXICITY:
MDF-0077 has been evaluated for mutagenic activity in the Ames bacterial reverse mutation assay using Salmonella typhimurium. There was no evidence of genetic activity for DMSO, ethanol or saline extracts of MDF-0077.
IMMUNOLOGY
1. NONSPECIFIC IMMUNE SYSTEM EFFECTS-
An imbalance of the regulatory network of the immune system may result in immune enhancement; e.g., hypersensitivity, or suppression; e.g., de-
creased resistance to infection. Silicone elastomer Q7-2423 was tested in
mice for a nonspecific (constitutive) modulation of the immune system using
a Listeria host resistance assay which primarily assesses competency of T lymphocytes and macrophages. This assay has been validated by National
Toxicology program. Female mice received cured 0.1 cm x 1 cm rods of
elastomer subcutaneously at 1 rod per mouse (surface area = 0.245 cm2).
This is equivalent to 863 cm2 elastomer surface area normalized to a 50 kg human. This surface area of one Dow Corning teardrop mammary implant is 401 cm2. Immunosuppression was demonstrated using cyclophosphamide and immunoenhancement using Corynebacterium paryum. Resistance
to Listeria infection was evaluated in terms of life-span and
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mortality 10, 45 and 90 days after elastomer implantation.
No treatment-related effects were found whether the data were evaluated separately or collapsed over the 3 exposure periods. Therefore, it was concluded that elastomer Q7-2423 under the conditions of the assay has no effect on immune competence.
2. SPECIFIC IMMUNE SYSTEM EFFECTS -
Silicone elastomer Q7-2423 was tested for immunologic sensitization potential in a granuloma model utilizing immune deficient nude mice (nu-nu) and their immunologically normal heterozygous littermates (nu/+). In this model, the challenge
granulomatous reaction at the site of material implantation in mice previously exposed to the same material can be distinguished as being immune regulated or a classic foreign body reaction that is not immune dependent. While a granulomatous reaction that is a simple foreign body reaction is not distinguished from an immunologically regulated granuloma on morphologic grounds alone, the latter exhibits memory. That is, the granulomatous response in a sensitized host is accelerated and/or amplified.
Q7-2423 was implanted subcutaneously as described above in nu/+ and nu/nu mice followed with a challenge implantation of Q7-2423 at the same dose at 28 days. At 2, 6, and 13 weeks thereafter the challenge implantation sites were evaluated with regard to capsule thickness, cellular composition, capsule cellularity and capsule connective tissue maturity. Comparisons of the sensitized (Q7-2423 +FCA) versus the nonsensitized (sham + FCA) mice were made for each mouse strain and exposure period using a series of statistical approaches; that is, chi-square, Mantel-Haenszel and Fisher's exact test). No PDMS treatment-related effects were observed for any of the 4 histological parameters measured.
Based on these findings it was concluded that the granulomatous response to Q7-2423 is of the class foreign body reaction type and not an immunologically active inflammatory response.
These studies of effects on the immune system demonstrate that silicone elastomer Q7-2423 is not inherently an immune adjuvant nor doe Q7-2423 at a relatively large subcutaneous dose cause immunoenhancement of immunosuppression in appropriate animal models.
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SUBCHRONIC TOXICITY

SUBCHRONIC ELASTOMER IMPLANTATION

GEL SPECIES DOSE DURATION RESULT
Q7-2222 Rabbit 4: 0.1x1 cm 3,10,30,90 FBR#
I.M. Days
2: 0.1x1 cm 3,10,30,90 FBR
S.Q. Days
Q7-2352 Rabbit 4: 0.1x1 cm 10,30,90 FBR
I.M. Days
2: 0.1x1 cm 10,30,90 FBR
S.Q. Days
Q7-2412 Rabbit *4: 0.1x1 cm 7,28,91 FBR
I.M. Days
2: 0.1x1 cm 7,28,91 FBR
S.Q. Days
Q7-2423 Rabbit 4: 0.1x1 cm 10,29,90 FBR
I.M. Days
2: 0.1x1 cm 10,29,90 FBR
S.Q. Days
Q7-2566 Rabbit 4: 0.1x1 cm 3,10,30,90 FBR
I.M. Days
2: 0.1x1 cm 3,10,30,90 FBR
S.Q. Days
Q7-2743 Rabbit 4: 0.1x1 cm 10,30,90 FBR
I.M. Days
2: 0.1x1 cm 10,30,90 FBR
S.Q. Days
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Q7-2744 Rabbit 4: 0.1x1 cm 10,30,90 FBR
I.M. Days
2: 0.1x1 cm 10,30,90 FBR
S.Q. Days
MDF-0081 Rabbit 4: 0.1x1.5 cm 7,28,91 FBR
I.M. Days
2; 0.1X1.5 CM 7,28,91 FBR
S.Q. Days
______________________________________________________________________
* 4 rods I.M. and 2 rods S.Q. per animal.
# Foreign Body Reaction

These subchronic studies reviewed here indicate that silicone system D elastomers are all associated with a foreign body reaction characteristic of a broad range of per-
sistent alloplastic materials such as the U.S.P. polyethylene employed as the control material in these studies. That is, an early acute inflammatory response is superseded by a chronic inflammatory phase (i.e., an infiltrate of predominantly macrophages) that transitions to fibroblastic activity and fibrous connective tissue encapsulation of the foreign body. A sparse dispersal of macrophages and giant cells may persist long-term although this is not characteristic of all implantation sites in all animals. This response pattern is the same for both intramuscular and subcutaneous implantation sites.
Another subchronic study in rabbits was designed to compare the local tissue response of the smooth silicone elastomer with the micro-pillared silicone elastomer.
Groups of 4 rabbits were implanted subcutaneously with one cm disks of elastomers as well as disks of materiel from competitive products; i.e., Biocell and Meme polyurethane coated shell. Groups were sacrificed at 7, 28, 56, and 91 days after implantation for histopathologic evaluation of the local tissue response.
There was a continuum of local foreign body response with the Meme polyurethane eliciting the greatest degree of acute and chronic inflammation, capsule formation, nonaligned fibroblast organization, disruptin of capsule collagen geometry and incidence of implant material particulates. The smooth silicone elastomer elicited the least response for all measured
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parameters. Biocell was intermediate in the degree of response and generally to a greater extent than observed for micropillared silicone elastomer.
CHRONIC TOXICITY
Several chronic elastomer studies are available as summarized in the following table.

CHRONIC ELASTOMER IMPLANTATION

MATERIAL SPECIES DOSE DURATION RESULT
Q7-2566 Rabbit 25 mg/Animal 1 Year FBR#
Knee Joint
25 mg/Animal 1 Year FBR
I.M.
Q7-2383 Rabbit 25 mg/Animal 1 Year FBR
Knee Joint
25 mg/Animal 1 Year FBR
I.M.
MDF-0077 Rat ~0.1x1 cm Rod 2 Year NAE**
S.Q.
Q7-4750 Rat *6: 0.1x1 cm Rods 2 Year NAE S.Q.
Q7-2423 Rat 8: 0.1x1 cm Rods 2 Year In-Process
S.Q.
MDF-0082 Dog 6: Rectangles 2 Year FBR
MDF-0083 Dog 6: Rectangles 2 Year FBR
MDF-0084 Dog 6: Rectangles 2 Year FBR
MDF-0085 Dog 6: Rectangles 2 Year FBR
MDF-0086 Dog 6: Rectangles 2 Year FBR
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MDF-0087 Dog 6: Rectangles 2 Year FBR
MDF-0088 Dog 6: Rectangles 2 Year FBR
MDF-0089 Dog 6: Rectangles 2 Year FBR
MDF-0099 Dog 6: Rectangles 2 Year FBR
Q7-2383 Rabbit 25 mg Particles 1 Year Granulomas
Joint Injection
______________________________________________________________________
*Number of elastomer rods/animal.
#FBR = Foreign Body Reaction
**NAE = No Adverse Effect

1. ON-YEAR RABBIT IMPLANTATION STUDY OF Q7-2566 AND Q7-2566 AND Q7-2383-Groups of 15 rabbits were implanted as outlined in the above table using elastomer spallation particles. There was a sham control group. Groups were sacrificed at 2, 4, 12, 24 and 52 weeks after implantation for histopathologic evaluation of the implanted paravertebral muscle and knee synovium and perisynovial connective tissue. Inguinal lymph nodes were also examined. The contralateral knee was examined as well. The reaction at the muscle site was a typical foreign body reaction as described previously. At the synovial and perisynovial sites the reaction varied from essentially none to a relatively mild inflammatory reaction; i.e., a granulomatous reaction. There was no evidence of pathologic change in the contralateral knee suggestive of an absence of a systemic immunologic reaction. There was no pathology observed in the inguinal lymph nodes.
2.TWO-YEAR RAT SUBCUTANEOUS IMPLANTATIONS STUDY OF MDF-0077 -
Groups of 50 male and 50 female rats were implanted subcutaneously with MDF-0077 in a study contracted to Industrial Bio-Test. The precise dimensions and number of elastomer rods is not clearly stated in the study report but was most probably a single rod per animal measuring 0.1x1 cm. U.S.P. polyethlene served as the control material. No adverse material-related effects were observed with regard to mortality, gross pathology or the type and incidence of tumors. This study does not conform to GLP regulations.
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3. TWO-YEAR RAT SUBCUTANEOUS IMPLANTATION STUDY OF Q7-4750 -
Q7-4750 is a system D (that is, platinum catalyzed) elastomer that differs from Q7-2423 only in that Q7-4750 is formulated with hexamethyldisilazane (HMDZ) while Q7-2423 is formulated without this reactive dimer. In final composition these elastomers are virtually identical in that HMDZ does not survive cure conditions.
A 2-year rat implantation study of Q7-4750 was recently completed and conformed to GLP regulations throughout. Groups of 50 rats per sex were implanted with 6 implants measuring 0.1x1 cm. Control groups of 60 rats per sex received an equal number of U.S.P. polyethylene rods as a material control. Two rods were placed I.M., 2 I.P. and 2 S.Q. There were no treatment-related adverse effects in terms of body weights, food consumption, mortality, clinical chemistry, hematology, organ weights, gross pathology or histopathology including tumor types or incidence. The absence of site-associated sarcomas demonstrated that the size and total surface area (1.47 cm2) of material implants falls below the threshold for solid-state tumorigenesis to be a detectable event.
4. TWO-YEAR RAT SUBCUTANEOUS IMPLANTATION STUDY OF Q72423 AND Q7-2551 -
The in-life phase of a 2-year rat implantation study of Q7-2423 and Q7-2551 was completed in January, 1991 and conformed to GLP regulations throughout. Groups of 60 rats per sex were implanted subcutaneously with 8 implants measuring 0.1 x 1 cm. Control groups of 60 rats per sex received an equal number of U.S.P. polyethylene rods as a material control. At the present stage of data analysis there are no known treatment-related adverse effects in terms of body weights, food consumption, mortality, clinical chemistry, hematology or organ weights. Histopathology is in-process.
5. TWO-YEAR IMPLANT STUDIES WITH SILASTIC MATERIAL IN DOGS -
Groups of 3 male and 2 female beagles were implanted S.Q., I.P. and I.M. with various combinations of a series of 9 system D elastomers. The elastomer samples were prepared as rectangles varying in size from 5/8 x 1-1/4 inches to 7/8 x 1 3/8 inches. A control group was not included. One dog of each sex in each group was sacrificed at 6 months after implantation and the remaining animals were sacrificed at 2 years. The implantation sites and selected tissues were examined histologically. No abnormal clinical signs were observed throughout, body weight was not affected and no
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changes in organ weights were noted. The reaction at the implantation sites was a typical foreign body reaction with fibrous encapsulation and chronic inflammation. Chronic inflammation was generally more evident at 6 months than at 2 years.
On the basis of these subchronic and chronic studies of closely related dimethyl system D elastomers it is concluded that:
1. Silicone system D elastomers are all associated with a foreign body reaction characteristic of a broad range of persistent alloplastic materials such as U.S.P.
polyethylene employed as the control material in these studies. That is, an early
acute inflammatory response is superseded by a chronic inflammatory phase (i.e., an infiltrate of predominantly macrophages) that transitions to fibroblastic activity and fibrous connective tissue encapsulation of the foreign body. A sparse dispersal of macrophages and giant cells may persist long-term although this is not characteristic of all implantation sites in all animals. This response pattern is the same for both intramuscular and subcutaneous implantation sites.
2. The results of elastomer implantation studies ranging in duration from a few days to 2 years demonstrate that reinforced silicone elastomers induce no detectable systemic adverse effects on any organ system.
3. Elastomer samples measuring 0.1x1 cm (0.245cm2)and total surface areas up to 2 cm2 per rat do no induce implantation site tumors (solid-state tumorigenesis) nor an excess of tumors remote from the implantation site.
ABSORPTION/DISTRIBUTION/METABOLISM/EXCRETION (ADME) -
Silicone elastomers are not subject to possible systemic distribution as might occur with PDMS or silicone gel. However, there has been speculation that the fumed amorphous silica used as a reinforcing filler in silicone elastomers may be available for distribution. This hypothesis has been evaluated by examining elastomer samples implanted subcutaneously in mice for up to 6 months for evidence of filler redistribution within the elastomer and for sign of change in the surface topography of the elastomer.
There was no degradation or surface modification of the elastomer observed using transmission electron microscopy at 1, 3 or 6 months after subcutaneous implantation. No alterations in silica distribution within the body of the elastomer or at the surface were observed at any time point.
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Therefore, this study demonstrated that the fumed amorphous silica used as a reinforcing silica maintains a stable distribution within the silicone elastomer. In addition, the surface morphology of the elastomer is not influenced by up to 6 months subcutaneous.
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techmedica
A company of SulzerMEDICA
JUNE 2, 1992

Diana Zuckerman
Congress of the United States
House of Representatives
Human Resources and Intergovernmental Relations Subcommittee
of the Committee on Government Operations
Rayburn House Office Building, Room B-372
Washington, DC 20516-6148

Dear Ms. Zuckerman:
Techmedica has designed and produced a limited number of patient specific Custom TMJ prostheses over the past 3-1/2 years for patients with severe degenerative TM Joint disease.
These implants employ biomaterials that have a long clinical history of successful use in orthopedics for reconstructing joints such as the hip and knee.
As in orthopedics, the goal of TM Joint replacement is to reduce pain while improving, mobility, function, and alignment of the affected limb or part.
It has been Techmedica's perception that the clinical problems associated with previous alloplastic (artificial) TMJ prosthesis were a result of poor implant material selection as well as use outside of the proper clinical utility where a more conservative treatment may have been preferable.
These implants have been available to a limited clinician group so as to facilitate patient follow-up at prescribed intervals. Although Techmedica actively pursues patient follow-ups there are invariably those patients that will become lost to this program. Fortunately data has and is currently being collected for the vast majority of these patients so as to evolve this product in a controlled and scientific way.
______________________________________________________________________
1380 Flynn Road Camarillo, CA 93012-8016 TEL:805-987-0466 800-541-9511
800-732-8535 CA Fax:805-987-4111
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Enclosed you will find clinical follow-up information for 95 patients over a two-year period. Also enclosed, are the ASTM specifications for the biomaterials comprising these devices and published articles regarding the use of these material for implants.
Sincerely,
signed
Dave Samson
Regulatory Affairs Manager
DS/cc
Enclosures
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TECHMEDICA CAD/CAM TOTAL TMJ PROSTHESIS
ANALYSIS OF DATA TO DATE, JUNE 1, 1992
LOUIS G. MERCURI, DDS, MS
CHICAGO, ILLINOIS

There are a total of 95 patients in the data set of this closely monitored limited clinical study. The average age of the patients is 42.02 (22-64) years. There are 5 males and 90 females with a total of 159 joints treated. These patients have averaged 10.3 (0-30) years of TMJ problems and undergone a mean of 5.32 (0-22) prior unsuccessful surgeries.
There has been 24 months of pre and post operative data that has been collected to date using a standardized data collection/format. Subjective data: pain, function of the mandible, and diet, are collected using a visual analogue scale (VAS) to objectify this data. Objective measures of mandibular range of motion read as interincisal opening and left and right lateral excursions were directly measured from the patient pre and post operatively.
Preliminary analysis of this data reveals a statistically significant decrease in pain (p<.004), increase in function (p<.002) and increase in diet (p<.007). There was improvement in mandibular range of motion recorded as well.
Tissue removed from the articular surfaces of a prosthesis functioning in a patient 2 years post CAD/CAM placement during the revision of scar tissue from around the joint revealed no evidence of a tissue reaction, or the fragments of metal or polyethylene when this tissue was examined histologically.
There have been 9 (5.6%) joints in which complications have been reported. One post operative wound infection requiring removal and replacement of the prosthesis; 3 early prostheses that did not fit properly and had to be remade; 3 prostheses in which the ramal component screws loosened necessitating replacement; and 2 early cases of condylar dislocation from the prosthetic fossa. This problem has been resolved with a design change which added a lip to the anterior of the fossa. There have been no cases of breakage, material or mechanical failure.
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MATERIALS AND ORTHOPAEDIC SURGERY

BY DANA C. MEARS, B.M., Ph.D., M.R.C.P., F.R.C.S.(C)

Associate Professor of Orthopaedic Surgery and Director of Orthopaedic Research, University of Pittsburgh.
Staff, Presbyterian-University Hospital, Children's Hospital, Pittsburgh, Penna.
Consultant, Veteran's Administration Hospital, Pittsburgh Penna.
Fellow, American Academy of Orthopaedic Surgeons.
Member, British Standards Committee for Surgical Implants.
American Society for Metals.
Fellow, Nuffield Orthopaedic Research, North American Orthopaedic Travelling,
Orthopaedic Audio-Synopsis Travelling.

With 900 Illustrations
handwritten - copyright 1979
The Williams & Wilkens Company
Baltimore
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MATERIALS AND ORTHOPAEDIC SURGERY
Winter and Shirley,38 described large numbers of orthopaedic implants after removal from human implantation. They reported the incidence of corrosion of metallic combinations of different austenitic stainless steel alloys (e.g., 18% chromium-8% nickel alloy with 18%chromium-8% nickel and 2.5% molybdenum) and of combinations of austenitic stainless steel alloys with a cobalt-chromium-molybdenum alloy. The alloys in combination did not show an increased incidence of corrosion compared to their behavior when used alone. Indeed, for combinations of stainless steel alloys, mutual protection seemed to be conferred by the combination. More recently, Cohen and Wulff39 have reported observations of the corrosion of a combination of a wrought cobalt-chromium-tungsten-nickel alloy with a cast cobalt-chromium-molybdenum alloy. Crevice crack was observed in the former alloy but not in the latter material. Laboratory tests were undertaken in which Teflon gaskets were applied to specimens of each cobalt-chromium alloy to form crevices between the metal and the polymeric material. The specimens were immersed individually in solutions of sodium chloride. Potential-time studies and metallographic observations showed that the cobalt-chromium-tungsten-nickel alloy underwent crevice attack, while the cobalt-chromium-molybdenum alloy did not undergo similar corrosion. The experiments confirm that the crevice corrosion in passive metals is provoked by the presence of a crevice on a susceptible alloy and not by the presence of dissimilar passive alloys.
Recently two types of total hip replacement have utilized combinations of dissimilar metals. The Muller type of total hip replacement,40 uses a cast cobalt-chromium alloy femoral head prosthesis welded to a wrought cobalt chromium alloy intramedullary stem. More recently, the latter alloy has been replaced with a titanium alloy (Ti-6A1-4V), also welded to the cobalt-chromium femoral head prosthesis. Both combinations have performed satisfactorily. The Russin modified Sivash prosthesis41 has combined a similar cast cobalt-chromium alloy with titanium. Again, this combination of materials has performed satisfactory in the clinical situation. Similar observations are required for other potentially useful combinations of dissimilar alloys.
Effects of Galvanic Currents on Tissues and Cells
There has been widespread speculation on the effects of corrosion currents on tissues and cells, although few facts are available. Corrosion may alter cells in at least three ways: (a) the metallic dissolution products may affect cell metabolism and thereby damage extracellular matrix; also (b) corrosion may be accompanied by changes in the chemical environmental of the cell, such as the production of hydrogen ions or hydroxyl ions or in the evolution of a gas such as hydrogen, oxygen or chlorine; and (c) the corrosion currents may affect cell behavior.
The first two factors are fully reviewed in Chapter 7. For cells exposed to metals singly or in combination, toxicity would be a function of the rate of the dissolution process of a particular dissolving anode and not of the presence of combinations of metals. At present, the effects of electric currents on cell behavior are under intense scrutiny. Observations of the effects of applying direct or alternating current to cell cultures reveal a variety of potentially beneficial as well as potentially harmful actions, including induction of osteogenesis, alignment of randomly oriented collagen fibers, transformation of red cell precursor cells into fully differentiated red cells, and stimulation of neuromuscular events. While the last mentioned has received the most attention as an adverse side-effect of implanted dissimilar metals, it is most unlikely to be clinically significant for the combinations of metals recommended in this chapter because the magnitude of electric power required for neuromuscular stimulation is orders of magnitude greater than corrosion currents between the recommended combinations of implant alloys. Ultimately the toxicity of corrosion potentials between dissimilar implant alloys must be assessed in the clinical situation. In the few large studies performed to date, the author is not aware of any deleterious biological response to implantation of combinations of the alloys, recommended here.
Conclusion
Even a cursory glance at present ambitious attempts to replace or repair human organs with man made devices will show the enormous advantage of the simultaneous use of a variety of alloys each selected for its particular mechanical attributes. In many cases, nonmetallic substances will also be required. A careful review of the electrochemical and biological effects of combinations of alloys shows that a wide variety of passive alloys may be safely used together in vivo. Admittedly, in the absence of expert knowledge of the properties of metals and alloys, it (page 124 of article)
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Component wear of total knee prostheses using Ti-6A1-4V, titanium nitride coated Ti-6A1-4V, and cobalt-chromium-molybdenum femoral components.
______________________________________________________________________ C. D. Peterson, B. M. Hillberry, and D. A. Heck*
School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47906

A knee simulator was used to study the wear of carbon fiber reinforced UHMWPE (Poly Two) (Poly Two is a registered trademark of Zimmer, USA) tibial and patellar
components against Ti-6A1-4V, titanium nitride (TiN)-coated Ti-6A1-4V, and cobalt-chromium-molybdenum femoral components. The prostheses tested were regular sized Miller-Galante total knees mounted on 316L stainless steel fixtures using bone cement. An environmental chamber surrounded the knee and maintained bovine serum lubricant at 37 deg C. The specimens were tested using consecutive blocks of 464 level walking steps, 8 ascending stairs and 8 descending stairs for a total of 100,000 steps. The wear mechanisms found on the tibial components were scratching, carbon-fiber associated damage, surface deformation, pitting, minor abrasion, and delamination. Three forms of carbon fiber associated damage were identified; fibers pulled from the surface, broken fibers, and UHMWPE removed from the surface fibers. The SEM evaluation revealed a pit forming mechanism. No correlation was found between femoral component material and tibial surface damage. Visual examination of the femoral components revealed no signs of wear or scratching on the cobalt-chromium-molybdenum or TiN-coated Ti-6A1-4V components. There were, however, many light surface scratches on the uncoated Ti-6A1-4V components, which were also observed in a supplementary test of an uncoated Ti-6A1-4V component tested with a conventional polyethylene tibial component.
______________________________________________________________________

INTRODUCTION

There has been considerable interest in the use of titanium, and especially the Ti-6A1-4V alloy, for orthopedic implants because of its biocompatibility, fatigue strength, and corrosion resistance. However, there has been some question of the wear resistance of Ti-6A1-4V against ultrahigh molecular weight polyethylene (UHMWPE).1 A number of studies have been conducted which evaluate the wear of Ti-6A1-4V and UHMWPE combinations under clean conditions and with acrylic contaminants.2 Within these studies a number of wear-resistant surface treatments have been evaluated, including nitriding, ion implantation, and special passivation techniques.3,4 These

*Associate Professor, Indiana University Medical Center, Indianapolis, Indiana
Journal of Biomedical Materials Research, Vol. 22, 887-903 (1988)
1988 John Wiley & sons, Inc. CCC 0021-9304-/88/010887-17$04.00
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studies have been run under sliding conditions, either pin-on flat or hip simulator studies.
Studies of the wear of Ti-6A1-4V against UHMWPE have had conflicting results. Rostoker and Galante 1,4 found that Ti-6A1-4V specimens exhibited scratches, black deposits, and abnormal wear in two studies of Ti-6A1-4V wearing against UHMWPE using a disk-on-flat geometry. These reports disagree with the results of Miller et al.5 and McKellop et al.,6 who found the wear characteristics of Ti-6A1-4V similar to those of stainless steel. In further tests, McKellop et al.2 found that Ti-6A1-4V is especially susceptible to abrasive wear from acrylic cement particles.
Several studies have been conducted using hip simulators, McKellop et al.7 studied the wear of hip prostheses with cobalt-chromium--molybdenum (Co-Cr-Mo) alloy and Ti-6A1-4V alloy femoral components using bovine serum lubrication. The tests were conducted under both clean conditions and with several approximately 2-mm-diameter fragments of PMMA cement placed in the acetabular cup. Under the clean conditions the Co-Cr-Mo ball had only light scratching and the titanium ball exhibited slightly more scratching. With acrylic chips present, the Co-Cr-Mo ball had only very light surface scratches, whereas the Ti-6A1-4V ball was severely scored and smeared with black residue. Greer,8 however, found that acrylic contaminants caused no change in the appearance of the Ti-6A1-4V femoral heads or the serum lubricant.
Rostoker and Galante3 found that special passivation techniques eliminated the abnormal wear of Ti-6A1-4V that they had previously reported.1,4 McKellop et al.9 reported that nitrided Ti-6A1-4V was virtually undamaged in a pin-on flat study that included acrylic contamination. Lucas et al.10 concluded that the corrosion characteristics of TiN coated and nitrogen ion implanted Ti-6A1-4V were very similar to those exhibited by the Ti-6A1-4V control samples, however there have been no studies published on the wear of these coatings against UHMWPE.
There have been two studies of UHMWPE wear of tibial components using knee simulators.11,13,14 Treharne et al.11 used a computer controlled simulator which controls the flexion angle and the joint load. Bovine serum lubrication at 37 deg C was used and wear was determined as weight loss from the tibial component using the method developed by McKellop et al.12 Wear debris which consisted of fibrous and, in some cases, granular or globular debris was recovered by Rose et al. 13,14 The prostheses with higher wear rates had regular periodic cracking. No correlation was found with molecular weight, but rather, it was concluded that the wear rate of UHMWPE knee components was dominated by contact stress.
Rose et al.15 examined the UHMWPE wear mechanisms of eight failed hip and 16 failed knee prostheses and found large craters in regions where there was no evidence of abrasion. Craters were found forming at the edges of UHMWPE fusion defects. Hood et al.16 in a retrieval study, found pitting on 90% of recovered tibial components. Much of the pitting appeared to be caused by acrylic debris; however, pits were also found in areas with no
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abrasion. In a 10-year retrieval study, Landy and Walker17 described fatique/delamination as a prominent wear mechanism where cracks and fusion defects eventually coalesced to produce wear fragments. Ainsworth et al, 18 in the original wear study on carbon fiber reinforced UHMWPE, (Poly Two)* found wear rates 3.8 to 10 times lower than for conventional UHMWPE; however, subsequent studies of carbon-fiber UHMWPE have found wear rates 1.8 times higher, 19 increased contact stresses and much higher fatigue crack propagation rates20 compared to UHMWPE.

METHODS

The prostheses were tested in a computer-controlled knee test machine 21 programmed to simulate walking and ascending/descending stairs. A schematic of the simulator, which as been used for a number of studies. 22,23 is shown in Figure 1. Motion and force plate date recorded from normal subjects4 is used as input to the computer. Hydraulic cylinders, operating in closed-loop control, impart the abduction/adduction force, the tibial torque at the "ankle" and the vertical force at the "hip". The quadracep cylinder is
insert figure one-Figure 1 Schematic drawing of knee simulator.21
*Poly Two is a registered trademark of Zimmer, USA
tData provided by Rush-Presbyterian Hospital, Chicago, Illinois
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connected to a cable which passes over a fixture holding the patella prosthesis and attaches to the "tibia." The simulator is operated at 0.4 cycles per second which is approximately one-half normal walking speed. The prostheses tested consisted of tibial, femoral, and patellar components. Polymethlmethacrylate (PMMA) was used to cement the components to stainless-steel fixtures. The knee joint was enclosed in an environmental chamber containing bovine serum, maintained at 37 deg C, as a lubricant.
Test protocol
A total of 10 tests were run during this testing program. The test specimens were Miller/Galente total knee prostheses donated by Zimmer, USA. The tibial component consisted of two parts, a metal tibial fixation plate and a carbon fiber reinforced UHMWPE (Poly Two) tibial articular surface component. The patellar buttons were also made of Poly Two. Three materials were used for the femoral articulating surfaces:
(1) Ti-6A1-4V titanium alloy (regular production--sterilized),
(2) Titanium nitride coated Ti-6A1-4V alloy (experimental prototype).
(3) Co-Cr-Mo alloy (regular production--sterilized)
Three prostheses of each type of femoral component were tested.
One supplemental test was run using an uncoated Ti--Ti-6A1-4V femoral component and conventional UHMWPE patella and tibial components. This test was run only to make visual comparisons with the femoral components being tested. The polyethylene tibial component was not compared.
Each test consisted of 100,000 cycles (100K) of simulated activity for an 82kg
(180 lb) subject. Each test was divided into 209 blocks. A block consisted of 464 level walking steps, 8 steps ascending stairs and 8 steps descending stairs. This approximates the ratio of level walking to stair climbing for normal activity.24 The third TiN coated prosthesis (TiN 3) was tested for an extended period for a total of 500,000 cycles of only level walking steps. In a previous study 23 seven different prostheses were tested for 100,000 walk cycles in the knee simulator using deionized water as a lubricant. In a retrieval comparison* the simulator tested prostheses showed the same damage modes, damage location, and severity that corresponded to approximately 2 years of clinical service with the exception that no pitting was observed in the simulator tested tibial components.
Visual, microscopic, and SEM evaluation
After testing, all femoral and tibial components were visually evaluated for surface damage. Following visual inspection, the tibial components received an additional inspection using a stereoscopic microscope at magnifications of x20 to x210. Tibial components surface damage was categorized according to
*Performed by Dr. T. M. Wright, Hospital for Special Surgery, New York
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COMPONENT WEAR OF TOTAL KNEE PROSTHESES
the seven damage modes used by Hood et al.16 plus an eighth category, carbon-fiber-associated damage. If distinct presence of a damage mode was observed, then this mode was recorded as existing for that prosthesis. Those tibial components which clearly illustrated one or more of the damage categories were then examined using a scanning electron microscope (SEM). The number of components examined with the SEM was limited because the required carbon coating contaminates subsequent observations.
Contact area measurements
Tibiofemoral static contact areas were measured before and after each test at knee flexion angles of 20 deg and 80 deg in all of the tests and additionally 40 deg in five of the tests. The 20 deg and 80 deg angles were selected to approximately correspond to those used by Wright et al.19 Contact areas were measured by inserting Prescale pressure sensitive film (Fuji Photo Film Company) between the tibial and femoral components and maintaining a vertical load at the "hip" of 32 Kg for 10 min.
Stability Test
The 100,000 cycle tests were interrupted at steps 1, 100, 400, 900, 4900, 9900, 49,900, and 100,000 to conduct stability tests.21 The stability test procedure was also conducted at the end of the 500,000-cycle test. In each stability test the machine is moved through five activities which study flexion performance as well as adduction/abduction (ad-ab) and tibial rotation stability. Vertical force applied at the "hip" for each assessment is 32 kg (70 lb). This reduced loading is used to avoid possible excessive loading during the stability test. The flexion performance routine holds the ad-ab force and tibial torque at zero while the knee is flexed from 10 deg to 40 deg and the quadriceps force is measured. The ad-ab stability routine holds the knee at 10 deg of flexion and tibial torque at zero, while the ad-ab displacement is measured. The tibial rotation stability routine holds the knee at 10 deg of flexion and ad-ab force at zero while the tibial torque is varied and tibial displacement is measured. The ad-ab and tibial rotation tests are repeated at 40 deg of flexion. Changes in stability are associated with the change in surface conformity. This is a reflection of the wear and/or deformation which occurs with cyclic loading. For the rotational stability tests hysteresis loops of the applied torque versus rotation is plotted. A least-squares fit is used to determine the rotational stiffness (torque per degree of rotation) of the prosthesis assembly under the 32 Kg vertical load applied to the "hip."
Wear measurement
Wear of the tibial components was characterized by the weight of material removed. The tibial and patellar components were presoaked in bovine
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serum at room temperature for a minimum of 14 days prior to the beginning of the test in order to minimize fluid absorption during the test. After presoaking, the parts were cleaned, vacuum desiccated and weighed on a Mettler H20 analytical balance. Following testing, the parts were again cleaned, desiccated and weighed. The amount of wear was the difference between the weights before and after the test. Fluid absorption during the test was corrected for by using a soak control similar to the one used by Treharne.11

RESULTS

Visual, microscopic, and SEM examination
On an unused Poly Two component, the surface has a glossy appearance and a layer of carbon fibers can clearly be seen in the surface plane, as shown in Figure 2. After testing in the simulator, the most common surface damage modes found were scratching and carbon-fiber-associated damage. Carbon-fiber-associated damage was defined as any surface disruption that was associated exclusively with the presence of carbon fibers. There were three different types of carbon-fiber-associated damage: fiber removal from the UHMWPE matrix, fiber breakage, and UHMWPE removal from fibers. Figure 3 shows the three modes of carbon-fiber-associated damage. The
INSERT FIGURE 2
Figure 2. SEM micrograph of unworn carbon fiber reinforced UHMWPE
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COMPONENT WEAR OF TOTAL KNEE PROSTHESES
INSERT FIGURE 3A & 3B
Figure 3. SEM micrograph of carbon fiber associated damage: (a) UHMWPE removal from carbon fibers, (b) trough from surface carbon fiber removal. (c) carbon fiber breakage.
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INSERT FIGURE 3C
areas of carbon-fiber-associated damage also exhibited the scratching mode of wear. Scratches, such as those seen in Figures 3(b) and 3(c) were aligned in the anteroposterior direction and were possibly due to the abrasive action of the broken fibers or removed particles of UHMWPE. Examination of the tibial component from the 500,000 cycle test shows the carbon-fiber associated wear mode when the surface layer of carbon fibers is present. In Figure 4(a), the UHMWPE removal and carbon fiber breakage modes of carbon fiber associated damage can be seen along with anterior/posterior scratches. The scratches shown were on the anterior edge of the lateral plateau wear zone. In the center of the wear zone, Figure 4(b), there are no surface fibers and relatively little UHMWPE damage, but anterior/posterior scratches are still present.
Surface deformation was noted in eight of the nine tibial components. No tests exhibited excessive surface deformation. The majority of the wear and deformation on the tibial components took place in the central and posterior areas of each tibial plateau. Also, the areas of wear and deformation extend to the medial edge of the medial plateau in five out of the nine prostheses tested. This implies that, during a step, some portion of the medial femoral condyle is not being supported by the tibial plateau. The central ridge of the tibial component constrains the femoral component when the knee is extended. However, the gap between the femoral condyles widens posteriorly allowing enough medial/lateral translation for the medial femoral condyle to be partially unsupported when the knee is flexed.
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COMPONENT WEAR OF TOTAL KNEE PROSTHESES
INSERT FIGURE 4A AND 4B
Figure 4. SEM micrograph of 500,000 step test's tibial component: (a) anterior edge of wear area, (b) center of wear area.
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Pitting was found on seven tibial components. In several cases it was evident that the process had begun with some abrasive or gouging process. In the other, however, there was no apparent abrasion, scratching, or gouging from which the pit began. Figure 5 shows a portion of a pit which was found of the posterior edge of the lateral condylar wear area of a tibial component. The carbon fibers visible at the bottom of the pit seem to be on the surface with no signs of carbon fiber ends, as if the pit were formed when UHMWPE pulled away from the carbon fibers that now make up the exposed surface. Figure 6 shows a pit that is in the process of forming along a surface made up of carbon fibers. The material being removed is surrounded by what appears to be a crack.
Two tibial components exhibited minor abrasion. These components had what appeared to be wide shallow scratches but under magnification showed areas where tufts of polyethylene extended away from the surface.
Table I lists the incidence of the tibial surface damage modes. Scratching and carbon fiber associated damage were found together on all nine tibial components. Surface deformation was found on eight and pitting was a wear mechanism on six of the tibial components. Minor abrasion was found on two of the tibial components. Embedded PMMA and burnishing were not observed on any of the tibial components. From the information summarized in Table I, no correlation could be found between the wear mechanism incidence and the femoral material.
INSERT FIGURE 5
Figure 5. SEM micrograph of a portion of large pit lined with carbon fibers.
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COMPONENT WEAR OF TOTAL KNEE PROSTHESES
INSERT FIGURE 6
Figure 6. SEM micrograph of pit forming along a boundary of three carbon fibers and a crack.
Contact area measurements
The results from the contact area measurements are shown in Table II. During the course of the study, contact area measurements were made before and after each test for a total of 28 different tests and flexion angle combinations. Of these combinations, 16 had an increase in contact area and 12 had a decrease in contact area. The variation in these results was caused by multiple stable assembly positions for a given flexion angle due to the relatively flat, unconstrained tibial component and multi-radius geometry of the femoral component.

TABLE I
Observed Damage Modes

______________________________________________________________________
Prosthesis Material and Test Number
Ti-6A1-4V TI-Ni- Co-Cr-Mo
Damage Mode 1 2 3 1 2 3 1 2 3 Totals
Surface deformation x x - x x x x x x 8
Pitting - x x - - x x x x 6
Embedded PMMA ~ - - - - - - - - - 0
Scratching x x x x x x x x x 9
Burnishing - - - - - - - - - 0
Abrasion - - - - x x - - - 2
Delamination - - - - - - - - - 0
Carbon Fiber Damage x x x x x x x x x 9
_________________________________________________________________________________
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TABLE II
Tibial Surface Contact Areas at Beginning and End of 100,000 Cycle Test
Contact Area (mm2nd)

______________________________________________________________________
Beginning of Test End of Test
Test 10deg 20deg 40deg 80deg 10deg 20deg 40deg 80deg
_________________________________________________________________________________
Co-Cr-Mo 89 68 80 89 84 54 69 84
Co-Cr-Mo 83 87 93 60 80 74 56 114
Co-Cr-Mo 92 81 80 63 80 88 88 105
Ti-6A1-4V 1 93 69 122 101 86 71 90 95
Ti-6A1-4V 2 - 64 - 79 - 79 - 78
TI-6A1-4V 3 - 82 - 79 - 87 - 97
Titanium nitride 1 - 45 - 69 - 86 - 85
Titanium nitride 2 - 56 - 94 - 70 - 56
Titanium nitride 3 80 103 93 98 82 83 82 93
_________________________________________________________________________________
Observations of femoral components
Figure 7 is a composite photograph of the lateral condyles of Co-Cr-Mo, Ti-6A1-4V, and TiN coated Ti-6A1-4V components after 100,000 steps of combined level walking and ascending/descending stairs activities. The femoral component photographs have marks oriented in the medial/lateral direction and lines forming an "H" shape. These marks and lines are reflections of the camera opening and photographer's enclosure, respectively. No visible scratching or other damage was found on the cobalt-chronium-
INSERT COMPOSITE PHOTOGRAPH
Figure 7. Lateral condyles of (a) Co-Cr-Mo, (b) Ti-6A1-4V, (c) TiN coated Ti-6A1-4V
femoral components.
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ASTM Designation F 67-89
Standard Specification for Unalloyed Titanium for Surgical Implant Applications1
This standard is issued under the fixed designation F67; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (<) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the chemical, mechanical, and metallurgical re-quirements for four grades of unalloyed titanium used for the manufacture of surgical implants.
1.2 The values stated in inch-pound units are to be regarded as the standard.
2. Referenced Documents
2.1 ASTM Standards
B 265 Specification for Titianium and Titanium Alloy Strip, Sheet, and Plate2
B 348 Specification for Titanium and Titanium Alloy Bars and Billets2
B 381 Specification for Titanium and Titanium Forgings2
E 8 Test Methods of Tension Testing of Metallic Materials3
E 16 Methods of Free Bend Test for Ductility of Welds4
E 120 Test Methods for Chemical Analysis of Titanium and Titanium Alloys5
E 190 Method for Guided Bend Test for Ductility of Welds3
E 290 Test Method for Semi-Guided Bend Test for Ductility of Metallic Materials3
F 981 Practic for Assessment of Compatibility of Biomaterials (Nonporous) for
Surgical Implants with Respect to Effect of Materials on Muscle and Bone6
2.2 Aerospace Material Specification:
AMS 2249C Chemical Check Analysis Limits Titanium and Titanium Alloys7
2.3 American Society for Quality Control (ASQC) Standard:
C1-1968 Specifications of General Requirements for a Quality Program8
3 General Requirements for Delivery
3.1 Material furnished to this specification shall conform to the requirements of the latest issues of Specifications B265, B348 and B381.
3.2 In the case where a conflict exists between this specification and those listed in 3.1, this specifications shall take precedence.
4 Ordering Information
4.1 Inquiries and orders for material under this specification shall include the following information:
4.1.1 Quantity (weight or number of pieces),
4.1.2 Grade (1, 2, 3, or 4),
4.1.3 ASTM designation,
4.1.4 Form (sheet, strip, plate, bar, billet or forging),
4.1.5 Condition (5.1).
4.1.6 Mechanical properties (if applicable, for special conditions),
4.1.7 Finish (5.2)
4.1.8 Applicable dimensions including size, thickness, width, and length
(exact, random, multiples) or print number,
4.1.9 Special tests, and
4.1.10 Special requirements
5 Manufacture
5.1 Condition--Material shall be furnished to the implant manufacturer in the
hot-rolled, cold-worked, forged, or annealed condition.
5.2 Unalloyed titanium material shall be free of injurious external and in-
ternal imperfections of a nature that will interfere with the purpose for
which it is intended. Annealed material may be furnished as descaled, as
sandblasted, or as ground, or both sandblasted and ground. If shipped as hot rolled, descaled, sandblasted, or ground, the manufacturer shall be permitted to remove minor surface imperfections by spot grinding
does not reduce the thickness of the material below the minimum per-
mitted by the tolerance for the thickness ordered.
6. Chemical Composition
6.1 The heat analysis shall conform to the requirements as to chemical composition prescribed in Table 1. Ingot analysis may be used for re-
porting all chemical requirements, except hydrogen, samples of which
shall be take from the finished product.
6.2 Product Analysis--Product analysis tolerances do not broaden the specified heat analysis requirements, but cover variations between labor-
atories in the measurement of chemical content. The manufacturer shall
not ship material that is outside the limits specified in Table 1 for applicable grade. Product analysis limits shall be as specified in Table 2.
6.2.1 The product analysis is either for the purpose of cont'd on page 285
_____________________________________
1. This specification is under the jurisdiction of ASTM Comittee F-4 on Medical and Surgical Materials and Devices and is the direct responsibility of subcommittee F04.02 on Resources.
<.Current edition approved Nov. 24, 1989. Published January 1990. Originally published as F67-88. Last previous edition F 67-88.
2. Annual Book of ASTM Standards, Vol 02.04.
3. Annual Book of ASTM Standards, Vol 03.01.
4. Discontinued--See 1977 Annual Book of Standards, Part 10
5. Annual Book of Standards, Vol. 03.05.
6. Annual Book of Standards, Vol 13.01.
7 Available from Society of Automotive Engineers, 400 Commonwealth Drive,
Warrendale, Pa 15096
8. Available from American Society for Quality Control, 161 W. Wisconsin Ave.
Milwaukee, WI 53203.
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F 67
Table 1 Chemical Requirements
INSERT TABLE 1
INSERT TABLE 2
INSERT TABLE 3
INSERT TABLE 4
verifying the composition of a heat or lot or to determine variations in the composition
within the heat.
6.2.2 Acceptance or rejection of a heat or lot of material may be made by the purchaser on the basis of this check analysis.
6.3 For referee purposes, Methods E 120 shall apply.
6.3.1 Samples for chemical analysis shall be representative of the material being tested. Extreme care must be taken in sampling titanium for chemical analysis because of its affinity for elements such as oxygen, nitrogen, and hydrogen. Therefore, when cutting samples for analysis, the operation should be carried out in a dust-free atmosphere, if possible. Chips should be collected from clean metal. Cutting tools should be clean and sharp. Samples for analysis should be stored in suitable containers.
7. Mechanical Requirements
7.1 Bar, billet, and forging shall conform to the appropriate requirements as to mechanical properties prescribed in Table 3. Sheet, strip, and plate shall conform to the appropriate requirements as to mechanical properties prescribed in Table 4. Grades 3 and 4 may be ordered in the cold worked condition to higher minimum tensile strength but a minimun 10 % elongation in 4D or 2 in (50mm) must be met.
7.2 For sheet and strip, the bend test specimen shall stand being cold through an angle of 105 deg without fractures in the outside of the bent portion. The bend shall be made on a diameter equal to that shown in Table 4 for the applicable grade.
7.2.1. Supplementary bend test requirements for sheet and plate are listed is S1.
7.3 Perform tension testing in accordance with Test Methods E8. Determine tensile properties using a strain rate of 0.003 to 0.007 in/in (mm/mm) min through the specified yield strength, and then the cross-head speed shall be increased so as to produce fracture in approximately one additional minute.
7.4 Any other special requirements shall be specified on the implant manufacturer's purchase order.
8. Certification
8.1 The manufacturer's certification that the material was manufacturered and tested in accordance with this specification together with a report of the test results shall be
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furnished to the implant manufacturers at the time of shipment.
9. Quality Program Requirements
9.1 THe producer shall maintain a quality program , such as for example, is defined in ASQC C1-1968.
9.2 The manufacturer of surgical implants or medical appliances shall be assured of the producer's quality program for conformance to the intent of ASQC C1-1968, or other recognized program.

SUPPLEMENTARY REQUIREMENTS

S. These requirements shall apply only when specified in the purchase order, in which event the specified tests and shall be made by the manufacturer before shipment of the plates.
S. Surface Requirements Bend Tests
S.1 The purpose of this test is to measure the cleanliness or ductility or both, of the metal surface.
S.2 Two guided- or free-bend tests of sheet or plate material limited to Grades 1, 2, and 3, shall be made. Each of these bends will place opposite surfaces of the sheet or plate material in tension.
S.3The bends are to be made in accordance with Method E 190 or Method E 16, except that the welds mentioned in these standards are not required. The bend specimen may be of less than full material thickness, however, the outer surface of the speciment must be representative of the product as supplied.
S1.4 The bend radius will be such to provide minimum elongation of the outer fibers of the bent specimens as follows:
Grade 1--20 % equivalent to 2T bend radius at 180 deg bend
Grade 2--20 % equivalent to 2T bend radius at 180 deg bend
Grade 3--16 % equivalent to 2-1/2T bend radius at 180 deg bend
S1.5 Criteria for acceptance will be the absence of any cracking or surface separations (not originating at the edge of specimen).

APPENDIX
(Nonmandatory Information)

X1. RATIONALE
X1.1 The primary reason for this standard is to characterize composition and properties to assure consistency in the starting material used directly or as modified by forging in the manufacture of medical devices.
X.1.2 The material compositions specified herein have been shown to produce a well-characterized level of local biological response following long term clinical use and has been used as control material in Practice F 981.
X.1.3 The choice of composition and mechanical properties dependent upon the design and application of the medical device.
X.1.4 A maximum limit for 0.2% offset yield strength has been added to the mechanical requirements for sheet, strip, and plate to coincide with Specification B 265.
X.1.5 The bend test sample thickness limits previously specified were incorrect. Supplementary bend test requirements have been added in accordance with Specification B 265.
X.1.6 Additional product analysis, tolerance, information, has been included for clarification purposes.
The American Society for Testing and Materials takes no position respecting the validity of patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
This standard is subject to recvision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, 1916 Race St. Philadelphia, PA 1910
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ASTM Designation F 136 -84
Standard Specification for Wrought Titanium 6A1-4V ELI Alloy for Surgical Implant Applications 1
This standard is issued under the fixed destination F 136; the number following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1.Scope
1.1 This specification covers the chemical, mechanical, and metallurgical requirements for wrought annealed Ti-6A1-4V E.L.I. (extra low interstitial) titanium alloy to be used in the manufacture of surgical implants.
1.2 The material in this specification has been subjected to testing in laboratory animals.2,3 The results of these studies and the clinical history indicate a well characterized level of local biological response.4,5
1.3 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents in parentheses are provided for information only.
2. Referenced Documents
2.1 ASTM Standards
B 265 Specification for Titanium and Titanium Alloy Strip, Sheet and Plate4
B 348 Specification for Titanium and Titanium Alloy Bars and Billets4
B 381 Specification for Titanium and Titanium Alloy Forgings4
E 8 Test methods of Tension, Testing of Metallic Materials5
E 120 Test Methods for Chemical Analysis of Titanium and Titanium Alloys6
E 290 Test Method for Semi-Guided Bend Test for Ductility of Metallic Materials7
F 620 Specifications for Titanium 6A1-4V ELI Alloy Forgings for Surgical Implants8
2.2 C1-1968 Specifications of General Requirements for a Quality Control Program9
3 Product classification
3.1 Strip--Any product under 0.1875 in (4.75 mm) in thickness and under 24 in (610 mm) wide.
3.2 Sheet--Any product under 0.1875 in. (4.75 mm) in thickness and 24 in. (610 mm) or more in width.
3.3 Plate--Any product 0.1875 in (4.75 mm) thick and over and 10 in. (254 mm) wide and over, with widths greater than five times thickness. Plate up to 1.75 in (44.45 mm), thick inclusive is covered by this specification.
3.4 Bar--Rounds from 3/16 in (7.9mm to 1.75 in (44.45 mm) in diameter. (Other sizes by special order.)
3.5 Forging Bar--Bar as described in 3.4 used for production of forgings, may be furnished in the hot rolled condition.
3.6 Wire--Rounds less than 3/16 in (4.8mm) in diameter.
4. Ordering Information
4.1 Inquiries and orders for material under this specification shall include the following information:
4.1.1 Quantity (weight or number of pieces),
4.1.2 Applicable ASTM designation,
4.1.3 Form (sheet, strip, plate, wire, bar, or forging),
4.1.4 Condition (See 5.1),
4.1.5 Mechanical Properties (if applicable, for special conditions),
4.1.6 Finish (see 5.2),
4.1.7 Applicable dimensions including size, thickness, width, or print number,
4.1.8 Special Tests, and
4.1.9 Special Requirements
5. Materials and Manufacture
5.1 The various titanium mill products covered in this specification are normally formed with the conventional forging and rolling equipment found in primary ferrous and nonferrous plants. The ingot metal for such mill operations is usually melted in arc furnaces of a type conventionally used for reactive metals.
5.2 Finish--Annealed material may be furnished to the implant manufacturer as de-scaled or pickled, sandblasted, ground, or combinations of these operations.
6. Chemical Requirements
6.1 The heat analysis shall conform to the chemical composition of Table 1. Ingot analysis may be used for reporting all chemical requirements, except hydrogen. Samples for hydrogen shall be taken from the finished mill product.
6.2 The product analysis tolerances shall conform to the check tolerances of Table 2.
6.3 For referee purposes, Methods E 120 shall be used.
6.4 Samples for chemical analysis shall be representative of the material being tested. The utmost care must be used in
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INSERT TABLES 1, 2 & 3
sampling titanium for chemical analysis because of its affinity for elements such as oxygen, nitrogen, and hydrogen. Therefore, in cutting samples for analysis, the operation should be carried out insofar as possible in a dust-free atmosphere. Chips should be clean and sharp. Samples for analysis should be stored in suitable containers.
7. Mechanical Requirements
7.1 Material supplied under this specification shall conform to the mechanical property requirements given in Table 3.
7.2 Specimens for tension tests shall be machine and tested in accordance with Test Methods E8. Tensile properties shall be determined using a strain rate of 0.003 to 0.007 in/in min (metric equivalent mm/mm/mm) through the specified yield strength.
7.3 For sheet and strip, the bend test specimen shall withstand being bent bold through an angle of 105 deg without fracture in the outside surface of the bent portion. The bend shall be made on a diameter equal to that show in Table 3. Test conditions shall conform to Test Method E 290
8. Special Requirements

8.1 The microstructure shall be a fine dispersion of the alpha and beta phases resulting from processing in the alpha plus beta field. There shall be no continuous alpha network at prior beta grain boundaries. There shall be no coarse elongated alpha platelets. There shall be no alpha case.

8.2 The beta transus temperature shall be measure by a suitable method and reported on the material certification.
9. Quality Program Requirements
9.1 The producer shall maintain a quality program such as, for example, is defined in Specifications C1-1968.
9.2 The manufacturer of surgical implants or medical appliances shall be assured of and may audit the producer's quality program for conformance to the intent of Specifications C1-1968, or other recognized program.
10. Marking, Packing, Certification and Rejection
10.1 Marking, packing, certification, and rejection shall be as specified in Specifications B 265, B 348, and B 381.

APPENDIX
(Nonmandatory Information)
X! RATIONALE

X1.1 The purpose of this specification is to characterize the chemical, physical, mechanical, and metallurgical properties of wrought annealed Ti-6A1-4V E.L.I. alloy to be used in the manufacture of surgical implants.
X1.2 The alloy composition covered by this standard has been employed successfully in human implants, exhibiting a
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well characterized level of local biological response, for over a decade.
X1.3 The microstructural requirements contained in this standard represent the current general consensus of opinion with respect to optimization of mechanical properties for implant applications.
X1.4 The minimum mechanical properties specified assure a baseline of strength and ductility for the highly stressed devices for which this alloy is typically tested.

The American Society for Testing and Materials takes no position respecting the validity of any patient rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
This standard is subject to revision of any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to ASTM Committee on Standards, 1916 Race St., Philadelphia, PA 19103.
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ASTM Designation: F 648 -84
Standard Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants1
This standard is issued under the fixed designation F 648; the number immediately following the designation indicates the year of original adoption or, in the case of revision. A number in parentheses indicates the year of last reapproval. A superior epsilon (<) indicates an editorial change since the last revision or approval.
1. Scope
1.1 This specification covers ultra-high molecular weight polyethylene powder (UHMWPE) intended for use in surgical implants.
1.2 The requirements of this specification apply to UHMWPE in two forms. One is virgin polymer powder (Section 4). The second is any form fabricated from this powder form from which a finished product is subsequently produced (Section 5). This specification addresses material characteristics and does not apply to the packaged and sterilized finished implant.
1.3 The provisions of Specifications D 4020 apply. Special requirements detailed in this specification are added to describe materials which will be used in surgical implants.
1.4 The biological response to polyethylene in soft tissue and bone has been well-characterized by a history of clinical use (1, 2, 3)2nd and by laboratory studies (4, 5, 6).
1.5 The following precautionary caveat pertains only to the test method portion, Section 7, of this specification: This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referred Documents
2.1 ASTM Standards
D 256 Test Methods for Impact Resistance of Plastics and Electrical Materials3
D 621 Test Methods for Deformation of Plastics Under Load3
D 638 Test Method for Tensile Properties of Plastics3
D 648 Test Method for Deflection Temperature of Plastics Under Flexural Load3
D 790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials3
D 1505 Test Method for Density of Plastics by the Density-Gradient Technique3
D 1898 Practice for Sampling of Plastics4
D 1921 Test Method for Particle Size (Sieve Analysis) of Plastic Materials4
D 2240 Test Method for Rubber Property--Durometer Hardness4
D 4020 Specification for Ultra-High Molecular Weight Polyethylene Molding and Extrusion Materials5
3. Description of Terms Specific To This Standard
3.1 fabricated form--any bulk shape of UHMWPE, fabricated from the virgin polymer powder, used during the process of fabricating surgical implants prior to packaging and sterilization.
3.1.1 Discussion--This form results from the application of heat and pressure to the virgin polymer powder, and the material characteristics of this form are subject to the applicable requirements of this specification. In present practice this includes extruded bars or molded blocks from which the final product form is machined, or a molded shape which is subsequently trimmed.
3.2 generic property--that property which is determined solely by the chemical composition and structure of the virgin polymer.
3.3 virgin polymer powder--the form of UHMWPE as obtained from the manufacturer and prior to fabrication into a bulk shape.
4. Virgin UHMWPE Powder Requirements
4.1 Generic Properties
4.1.1 The virgin polymer shall be a homopolymer of ethylene, as described in Specification D 4020.
Note 1--Information on the degree of branching, methyl group concentration and vinylidene content would be useful. Presently, there is not a suitable method to determine the parameters.
4.1.2 Molecular weight of the polymer powder shall be indicated by determining the relative solution viscosity. The relative solution viscosity, when determined in accordance with the method given in Specification d 4020, shall be 2.30 or greater. The accuracy of the test results shall be determined by vendor-purchaser agreement.
Note 2- While the precise relationship between the bulk properties and wear resistance of implants and the molecular weight of the polyethylene used to fabricate them has not been established quantitatively, it has been demonstrated that UHMWPE is more suitable for such applications that are polyethylenes of lower molecular weight.
The relative solution viscosity of dilute solutions of UHMWPE powder may be used as adequate indicators that con't on page 291
______________________________________________________________________
1. This specification is under the jurisdiction of ASTM Committee F-4 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.02 on Resources.
Current edition approved Sept 28, 1984. Published February 1985.
2. The boldface numbers in parentheses refer to the list of references at the end of this specification.
3. Annual Book of ASTM Standards Vol 08.01
4. Annual Book of ASTM Standards Vol 08.02
5. Annual Book of ASTM Standards Vol 08.03
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ASTM F 648
some minimum value of molecular weight is attained. At present, there is some uncertainty regarding the extension of the solution viscosity/molecular weight relationship to the UHMWPE range.
Information on the molecular weight distribution would permit control of the weight fraction of low-molecular weight material. Presently, there is not a suitable method to determine the distribution.
4.2 Nongeneric Properties:
4.2.1 The polymer powder shall contain as little extraneous matter (such as dirt, lint, silica, and discoloring material) as possible. The purchaser and vendor shall agree on which of the following test methods will be used.
4.2.1.1 When a 400 cm2nd sample prepared in accordance of 7.1.2.1 is viewed, there shall be no particle whose largest dimension is greater than 300pm and there shall be no more than 10 particles whose largest dimension is 300 pm or less.
4.2.1.2. When a 300-g sample prepared in accordance with 7.1.2.2 is viewed, there shall be no more than 25 particles present.
4.2.2 The polymer powder shall contain as few trace elements as possible, and the level of those trace elements shall be as small as possible. To promote uniformity between different lots of polymer powder, the following maximum concentration limits for trace elements have been established.
ELEMENT pp.max
Al 100
Ti 300
Ca 100
Cl 120
4.2.2.1 Analysis for these and other elements shall be conducted by vendor-vendee agreement.
Note 3. There is no evidence that the concentration of trace elements affects the physical properties of the biological response of UHMWPE fabricated forms.
4.2.3 All powder shall pass a No. 16 (1.18-mm) sieve.
Note 4--A limitation on particle size stems from the possibility that excessively large particles of UHMWPE may not flow enough in subsequent "sintering" or molding operations to yield a sufficiently fused material. This could result in undesirable local inhomgeneity or a porous structure.
5. UHMWPE Fabricated Form Requirements
5.1 Compositional Requirements:
5.1.1 Bo stabilizers or processing aids are to be added to the virgin polymer powder during manufacture of a fabricated form.
5.1.2 The surface of a fabricated form shall contain as little extraneous matter as possible. When a 400-cm2nd sample prepared in accordance with 7.2.2 is viewed, there shall be no particle whose largest dimension is greater than 300 pm, and there shall be no more than 10 particles whose largest dimension is 300 pm or less.
5.2 Physical Requirements:
5.2.1 The surface of a fabricated form shall contain as few light patches (which would indicate unfused areas) as possible. When a 400-cm2nd sample prepared in accordance with 4.2.2 is viewed, there shall be no light patch whose largest dimension is greater than 300 pm.
5.2.2 The density of the fabricated form shall be between 0.930 and 0.944 g/cm3rd.
5.3 Mechanical Requirements:
Note 5--The relationship between these mechanical properties and the in vivo performance of a fabricated form has not been determined. While trends are apparent, specific property-polymer structure relationships are not well-understood. These mechanical tests are frequently used to evaluate the reproducibility of a fabrication procedure and are applicable as quality control tests to determine lot to lot repeatability for a process of converting virgin polymer powder to a fabricated form. The mechanical properties are subject to variation as the fabrication process variables (such as temperature, pressure, and time) are changed.
5.3.1 UHMWPE in fabricated form from which implants shall be made shall meet the requirements listed in Table 1.
Note 6--The following mechanical tests may be conducted based on agreement between the vendor and purchaser:
(1)Deflection temperature: Test Method D 648 (1.8 MPa 264psi)
(2)Flexural modules. Test Methods D 790 (sccant. 2 % offset)
6. Sampling
6.1 Where applicable, the requirements of this specification shall be determined for each lot of powder and fabricated form by sampling sizes and procedures according to Recommended Practice D 1898, or as agreed upon between the purchaser and seller.
7. Test Methods
7.1 UHMWPE Powder:
7.1.1 Determine the relative solution viscosity in accordance with the method given in Specification D 4020.
7.1.2 Determine the amount of extraneous matter by the following procedures as agreed by the vendor and purchaser.
7.1.2.1. Using a polished steel mold, press UHMWPE powder into sheets with a minimum surface area of 12 cm2nd and a maximum thickness of 6.0mm, at 205+/- 10 deg C (400 +/- 18degF) for 10 min. Examine a total surface area of 400cm2nd. Count the particles using optical microscopy within the translucent sheets.
7.1.2.2 A 300-g sample is divided into four 75-g samples. Place a 75-g sample in each of four 1000 mL Erlenmeyer flasks, add 400 mL isopropyl alcohol, shake 5 min, and let settle for 5 min. Count the total number of particles of extraneous matter in the four flasks.
7.1.3 Determine the trace element concentration by the following methods or by methods agreed upon by the vendor and purchaser:
Ti Atomic absorption or emission spectroscopy
Al Atomic absorbtion or emission spectroscopy
Ca Atomic absorption or emission spectroscopy.
Cl Potentiometric methods or titration methods
7.1.4 Ensure that the particle size of the powder is correct by passing it through a No. 16 (1.18mm) sieve in accordance with Method B of Test Method D 1921.
7.2 UHMWPE Fabricated Form
7.2.1 The requirements that there will be no addition of any stabilizer or processing aid during fabrication of the fabricated form shall be met by certification of the fabricator .
7.2.2 Use optical microscopy to determine the size of the particles of extraneous matter and the size of light patches at the surface of the fabricated form. Examine a surface area of 400 cm2nd taken from locations within the fabricated form agreed upon by the vendor and the purchaser.
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ASTM F648
Insert Table 1
7.2.3 Determine the density in accordance with Test Method D 1505.
7.2.4 Determine specific mechanical properties in accordance with the methods listed in Table 1. Mechanical test specimens shall be produced by methods that represent those used to produce surgical implants.
References
(1) Charnley, J., Cupiz A., "The Nine and Ten Year Results of the Low Friction Arthroplasty of the Hip," Clinical Orthopaedics. Vol. 95, No. 9, 1973.
(2) Halley D., Charnley, J., "Results of Low Friction Arthroplasty in Patients Thirty Years of Age or Younger." Clinical Orthopaedics, No. 112, October 1975.
(3) Mirra, J., Amstutz, H., Matos, M., Gold, R., "The Pathology of the Joint Tissues and Its Clinical Relevance in Prosthesis Failure," Clinical Orthopaedics, No. 117, June 1976.
(4) Turner, J., Lawrence, W., Autian, J., "Subacute Toxicity Testing of Biomaterials Using Histopathologic Evaluation of Rabbit Muscle Tissue., Journal of Biomedical Materials Research, Vol. 7, 1973.
(5) Laing, P., "Compatibility of Biomaterials," Orthopedic Clinics of North America, Vol. 4, No. 2, April 1973.
(6) Escalas, F., Galante, J., Rostoker, W., Biocompatibility of Materials for Total Joint Replacement," Journal of Biomedical Materials Research, Vol 10, No. 2, 1976.
The American Society for Testing and Materials takes no position respecting the validity of any patent rights assorted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk Infringement of such rights, are entirely their own responsibility.
This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not reviewed, either reapproved or withdrawn. Your comments are invited either for revision of the standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to ASTM Committee Standards, 1916 Race St., Philadelphia, PA 19103
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ASTM Designation F 799 - 87
Standard Specification for Thermomechanically Processed Cobalt-Chromium-Molybdenum Alloy for Surgical Implants1
This standard is issued under the fixed designation F 799, the number immediately following the designation indicates the year of original adoption or, in the case, of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superior epsilon (<) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers the material requirements of high strength, thermomechanically processed, cobalt-chromium-molybdenum alloys used for surgical implants. Material conforming to this specification has been evaluated for biocompatibility and corrosion resistance2 and has been found to be comparable to material conforming to Specifications F75. The properties specified in this document specifically apply to finished or semifinished parts that receive no subsequent metallurgical processing.
1.2 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of the inch-pound units may be approximate.
2. Referenced Documents
2.1 ASTM Standards:
E 8 Methods of Tension Testing of Metallic Materials3
E 18 Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Material3
E 112 Methods for Determining the Average Grain Size3
E 354 Methods for Chemical Analysis of High Temperature, Electrical, Magnetic and Other Similar Iron, Nickel and Cobalt Alloys4
F 75 Specification for Cast Cobalt-Chromium-Molybdenum Alloy for Surgical Implant Applications5
F 981 Practice for Assessment of Compatibility of Biomaterials (Non-porous) for Surgical Implants with Respect to Effect of Materials on Muscle and Bone5
2.2 Aerospace Material Specifications6
AMS 2269C Chemical Check Analysis Limits, Wrought of Nickel Alloy and Cobalt Alloys
AMS 2248B Chemical Check Analysis Limits, Wrought Heat, and Corrosion-Resistant Steels and Alloys
2.3 American Society for Quality Control Standard:7
ASQC C1-1968 Specification of General Requirements for a Quality Program.
3. Significance and Use
3.1 The purpose of this specification is to characterize the material properties of currently available cobalt-chromium-molybdenum implant parts manufactured by processes other than conventional techniques.
4. Ordering Information
4.1 Inquiries and orders for material under this specification shall include the following information:
4.1.1 Quantity
4.1.2 ASTM designation and date of issue
4.1.3 Mechanical properties
4.1.4 Form (semifinished parts, part No.),
4.1.5 Applicable dimensions or print number
4.1.6 Condition (as hipped, forged, heat treated, annealed),
4.1.7 Special tests, and
4.1.8 Other requirements.
5. Condition
5.1 Finished or semifinished parts conforming to this specification may be prepared by a variety of methods including powder consolidation and forging; and may be in a heat-treated, hot-worked or annealed condition.
6. Chemical requirements
6.1 The cobalt-chromium-molybdenum alloy supplied to the manufacturer for the production of surgical implants shall conform to the chemical composition limits specified in Table 1. The product analysis tolerances shall conform to the requirements in Table 2.
7. Mechanical Requirements
7.1 Tensile Properties
Table 1 chemical requirements
Composition %
min max
Chromium 26.0 30.0
Molybdenum 5 7
Nickel - 1.0
Iron - 0.75
Carbon - 0.35
Silicon - 1.0
Manganese - 1.0
Nitrogen - 0.25A
Cobalta balance
______________________________________________
A #N<0.10 contents does not have to be reported.
a Approximately equal to the difference between 100 % and the sum percentage of the other specified elements. The percentage of cobalt by difference is not required to be reported.
________________________________________________________________________
1. This specification is under the jurisdiction of ASTM Committee F-4 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.02 on Resources.
Current edition approved Sept 25, 1987. Published November 1987. Originally published as F 799 - 82. Last previous edition F 799-82.
2. Supporting data are available on loan from ASTM Headquarters, 1916 Race St., Philadelphia, PA 19103. Request Research Report RR:F04-0000
3. Annual Book of ASTM Standards. Vol. 03.01
4. Annual Book of ASTM Standards Vol. 03.05
5. Annual Book of ASTM Standards Vol. 13.01
6. Available from Society of Automotive Engineers, 400 Commonwealth Drive,
Warrendale, Pa 15096
7. Available from American Society for Quality Control, 161 W Wisconsin Ave, Milwaukee, WI 53203
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ASTM F 799
Table 2 Product Analysis TolerancesA
Element Permissible Variation Under the
Minimum Limit or Over the Maximum
Limit % a
Chromium 0.30
Molybdenum 0.15
Nickel 0.05
Iron 0.03
Carbon 0.02
Silicon 0.05
Manganese 0.03
Nitrogen c 0.02
A Refer to AMS Standard 2269C for Chemical Check Analysis Units (except nitrogen)
a For elements where only a maximum percentage is indicated, the "under minimum limit" is not applicable
c Refer to AMS 2248B
Table 3 Mechanical Requirements
____________________________________________________________________________________Ultimate Tensile Yield Strength
Strength min, ().2 % offset Elongations,A Reduction in Hardness
psi (MPa) min, psi (MPa) min, % Area, min% Rc4 min
____________________________________________________________________________________
170 000 (1172) 120 000 (827) 12 12 35
A Gage length in - 4 x diameter

7.1.1 Tensile properties shall be determined in accordance with Methods E 8.
7.1.2 The mechanical properties of test specimens prepared from finished or semifinished parts shall conform to the requirements in Table 3.
7.1.3 Tensile specimens shall be produced from finished or semifinished parts or from material having the same process history as that which exists in the final surgical implant device. Tension specimens may have a ground finish on the reduced section and may be taken in a direction parallel to the long axis of the finished or semifinished part.
7.1.4 A minimum of two test specimens shall be tested. If one specimen falls below the specified tensile requirements or breaks outside the gage limits, two additional specimens shall be tested and both must pass.
7.2 Hardness-Finished or semifinished parts conforming to this specification shall have a minimum Rockwell C hardness of 35 HRC. The hardness determination shall be performed in accordance with Methods E 18.
8. Special Tests
8.1 Finished or semifinished parts conforming to this specification shall have a homogenous microstructure with a grain size of ASTM No. 5 or finer when measured in accordance with Methods E 112.
9. Certification
9.1 A certification shall be provided by the alloy producer that the material meets the requirements in Table 1.
10. Quality Program Requirements
10.1 The alloy producer and any processors shall maintain a quality program such as, for example, is defined in ASQC C1-1968.
10.2 The manufacturer of surgical implants or medical devices shall be assured of the producer's quality program for conformance to the intent of ASQC C1-1968 or other recognized programs.

APPENDIX
(Nonmandatory Information)
X!. RATIONALE

X1.1 The purpose for this standard is to characterize composition and properties to assure consistency in thermomechanically processed cobalt-chromium-molybdenum finished or semifinished parts used in the manufacturing of medical devices that receive no subsequent metallurgical processing.
X1.2 Material conforming to this specification has been evaluated for biocompatibility and corrosion resistance and has been found to be identical to material conforming to Specification F 75. Materials conforming to Specification F 75 have been used as a control in Practice F 981.
X1.3 Published data 8,9 indicate that material with a fine grained homogenous metallurgical structure resulting from thermomechanical processing will be superior with respect to tensile strength and fatigue resistance compared to material conforming to Specification F 75. Based upon this, requirements include fine-grained microstructure and high tensile strength.
X1.4 The maximum iron content has been lowered to coincide with compositions that are commercially available.
____________________
8 Bardos, D. I., "High Strength Co-Cr-Mo Alloy for Prostheses," Current Concepts of Internal Fixation of Fractures, edited by H. Ubthoff, Springer Vertag, New York, NY 1980, p 111.
9 Weisman S., "Vitallium FHS Forged High-Strength Alloy," Current Concepts of Internal Fixation of Fractures, p 118.
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ASTM F 799
The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity
of any such patent rights, and the risk of infringement of such rights are entirely their own responsibility.
This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not reviewed, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive careful consideration of a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, 1916 Race St., Philadelphia, PA 19103
(295)
HTML>Ion implantation of cobalt-chromium prosthetic components to reduce polyethylene wear
by Piran Sioshansi, PhD an Orthopedics Today Essay

The wear of ultra-high molecular weight polyethylene (UHMWPE) is a significant problem affecting the longevity and performance of prosthetic total joints.
With improved designs for cemented and cementless applications and recent progress in improving short and long term fixation of implants, it is becoming increasingly important to resolve the problems associated with polyethylene wear. Polyethylene wear debris is believed to cause macrophage response and granulomas/ and other complications that promote loosening or interfere with prosthetic joint performance and longevity.
Polyethylene is currently the only suitable material for total joint articular applications. It combines many desirable inherent properties such as low friction, good biostability, and good formability and machinability.
However, polyethylene wear and associated debris remains a major problem. Recent reports indicate polyethylene's linear wear rate is on the order of 200 microns per year in a typical hip prosthesis, amounting to 2 mm of wear in 10 years of operation.
Attempts to find an adequate substitute material for polyethylene have not been totally successful, and no new material is expected to become available in the near future. Therefore, finding a scientific method to address the polyethylene wear issue and overcome the problem of polyethylene wear debris is of great importance in total joint replacement applications.
The results of a recent study at Spire Corporation indicate that the ion implantation process, a technology already well established for treatment of titanium alloy orthopedic implants, is extremely effective when applied to cobalt-chromium (Co-Cr) orthopedic bearing components in minimizing the wear of UHMWPE. Spire markets the ion implantation process under the tradename Ionguard. (R) Ion implantation of Co-Cr to reduce polyethylene wear is specifically designated Ionguard-II.TM
Initial funding for this research was provided by the National Institutes of Health through a grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, awarded to Spire in 1990. Extensive research efforts in this have now been
productive in identifying the optimal process parameters for mini-mixing wear of polyethylene.
ION IMPLANTATION TECHNOLOGY
In the ion implantation process, the surface of a Co-Cr orthopedic component is exposed to energetic ion beams in a vacuum chamber. An active ion species such as nitrogen impinges on the surface of the Co-Cr alloy, interacting with the material to beneficially alter the physical and chemical structure of the surface.
Changes in the physical structure are generally due to interaction of incoming energetic particles with the alloy's crystalline structure. The solid state structure is altered, resulting in smaller grains with a pseudo- amorphous structure. The chemical structure is altered by the interaction of the incoming nitrogen with the host chromium atoms, forming small hard phase chromium nitride precipitates. These physical and chemical changes in the Co-Cr surface produce a lower coefficient of friction and a harder, more homogenous surface structure.
An inherent and extremely important feature of the ion implantation process is the resulting change in surface energy of the treated material. Ion implanted surfaces typically show a higher energy, as demonstrated by water contact angle measure-ments. This is extremely desirable for improving tribological properties of lubricated materials in relative motion. It is generally believed that a hydrophilic material with a high surface energy improves the ability of the surface to hold a liquid film. Thus, the metal/polymer contact during articulations minimized, and the resulting wear is drastically reduced.
Ion implantation is the high technology approach for altering surface properties of materials without adversely affecting the desired bulk properties. Ion implantation is applied at room temperature inside a high vacuum, clean environment. The process does not alter surface finish or dimensional integrity of the parts; thus, it is readily applicable to finished delicate medical components.
The technology's greatest attribute is its excellent reliability, reproducibility, and built-in process control, virtually guaranteeing 100% yield for batch processing of orthopedic components. The technology, has already an established place in pro-cessing of titanium-based orthopedic implants, where the interest is to eliminate metallic wear debris that may occur during articulation against UHMWPE. Wear of cobalt chromium, per se, is not a concern. The-cont'd on page 297
Reprinted from Orthopedics Today, 1991, Vol. 11, No.8
Copyright 1991. Slack Inc., Medical Publisher. All rights reserved.
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INSERT FIGURES 1, 2, 3, & 4
primary goal for pursuing ion implantation with Co-Cr components is to reduce wear in the opposing UHMWPE surface.
THE EXPERIMENT
A carefully designed and executed research program has been completed for comparing the wear of polyethylene in contact with control and ion implanted cobalt-chromium surfaces, as well as zirconia ceramic.
Pins of Co-Cr and zirconia with identical geometries were prepared for testing in a pin-on-disk tribosystem. The experimental set-up consisted of 3.2 mm radius hemispherical-tipped pins in contact with 6.4 mm thick, 28.6 mm radius UHMWPE disks. The pins were circulated on the disks at 90 revolutions per minute, wearing a 9.5 mm radius track. All disks were gamma sterilized prior to testing. The surface finish of both types of pins was approximately 2 pin RMS and that of the disks was approximately 0.5 pm.
The load of the pins was 10 N, which produced an initial peak Hertzian contact stress of approximately 59 MPa. However, the Hertzian stress was estimated to decrease to 15 Mpa after a short time, due to compression in the polyethylene. This value is below the yield strength of UHMWPE.
The pin-on-disk tests were run for 123,000, 370,000 and 1 million cycles in bovine blood serum at room temperature. The bovine serum was replaced on a daily basis for the longer runs by stopping the experiments, suctioning the liquid out and replacing it with fresh serum.
Several additional test were performed to characterize the changes effected by ion implantation in the cobalt chromium alloy. Coefficient of friction between the pin and disk was monitored throughout the wear testing, and surface energy determinations were made via water contact angle measurements. Microhardness measurements were made on a Buehler MIcrohardness Tester under a load of 2 g.
RESULTS
Wear results were obtained by disassembling the pin-on-disk couple and measuring the groove on the polyethylene disk. The volume of the groove was measured by a standard profilometer and was attributed to be a combination of cold flow (compression or creep) as well as wear. To separate the two factors, several experiments were run to only 5,000 cycles. Testing showed the groove at this point is due entirely to cold flow. All subsequent measurements, taken at periods of 123,000 cycles, 370,000 cycles and 1,000,000 cycles, were corrected for this cold flow measurement. That is, the difference in volume between the grooves measured in the longer tests and the grooves measured in the 5,000 cycle test is attributed to wear.
Representative wear track profiles are show in Figure 1 for each test length. The wear tracks for the control tests increase in size with test length. However, the wear tracks for the disks opposite the ion implanted
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INSERT FIGURE 5 & 6
pins remain essentially constant. Here, a small groove, attributed entirely to compression, appears after 5,000 cycles, but as the test progresses the size of the groove does not increase, indicating that no appreciable polyethylene wear is occurring.
Mean corrected UHMWPE wear results are compared in Figure 2 for ion implanted and control cobalt-chromium. Results of the test conducted using the ceramic pin are also shown for comparison. These results show that the ion treatment of Co-Cr virtually eliminates wear in polyethylene, performing even better than the much more expensive ceramic parts.
Additional test showed that ion implantation had several notable effects on the Co-Cr surface. Microhardness increased 42% at a 2 g load, from 611 to 867 (Fig. 3), and friction against UHMWPE decreased from 0.131 to 0.089 (Fig. 4). The water contact angle tests showed a substantial increase in surface energy. The contact angle changed from 82 to 52 with a lower angle indicating increased surface energy (Fig. 5).
DISCUSSION
Preliminary pin-on-disk results show that ion implantation significantly reduces the wear of the polyethylene in contact with cobalt-chromium components by approximately three orders of magnitude. Close examination shows the ion treated cobalt-chromium has a lower coefficient of friction, increased surface hardness, and much higher surface energy (hydrophilic), as measured by the water contact angle technique.
The increased wetability of the surface and lower coefficient of friction are significant factors in reducing UHMWPE wear. However, these properties cannot, by themselves, explain the negligibly small wear on the ion implanted Co-Cr surface measured in the current study. Zero wear can only be explained in the context of much higher surface energy induced on the Co-Cr components.
Increased surface energy improves the hydrophilicity of the surface and, thus, the ability of the surface to retain a liquid film. The liquid film, in turn, minimizes the contact between polyethylene and ion treated cobalt-chromium bearing surfaces, and thus limits the probability of asperity interlocking and plowing action on the UHMWPE that is responsible for creating wear debris.
CONCLUSIONS
Ion implantation of Co-Cr orthopedic joints appears to be effective for addressing the wear of ultra-high molecular weight polyethylene. Ion implantation increases surface wetability, reduces the coefficient of friction, and improves surface hardness on Co-Cr alloys.
Preliminary pin-on-disk experiments show that the wear of polyethylene in contact with ion treated Co-Cr components is negligibly small. The near zero polyethylene wear can be explained by the liquid film that ion treated cobalt-chromium surfaces can retain. Ion implantation increases the surface energy and thus, the ability of cobalt chromium to retain a liquid film (bovine serum or synovial fluid), minimizing contact between polyethylene and cobalt-chromium surfaces.
Ion implantation technology offers great advantages as a reliable, reproducible process for treatment of sensitive orthopedic products.
PRODUCT AVAILABILITY
Spire Corporation has entered into an ion treatment production processing contract with Osteonics, a division of Stryker Corporation.
Under the terms of the contract, Osteonics has committed to treating an entire product line with the process. In return, Spire Corporation has offered Osteonics an exclusive arrangement for the duration of the contract. Ion implanted hip components have been in the manufacturing since the beginning of May, and the product was launched on June 15, 1991. Ion treated Co-Cr knee components (Fig. 6) are scheduled for availability in August.
Osteonics has named its ion treated cobalt-chromium hips and knees LFIT(R) (Low Friction Ion Treated).
Dr. Sioshansi is vice president, Surface Engineering Division, Spire Corporation (Patriots Park, Bedford MA 01730)
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THE 1992 CONGRESSIONAL HEARINGS! PART 4! JUNE 4, 1992

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