Authors: John S. Thalgott, M.D., James M. Giuffre, B.A., Kay Fritts, R.N.,
Accepted for Poster Presentation Meeting  Year---
   International Society for the Study of the Lumbar Spine  1996
Abstract

Introduction: With the advent of transpedicular fixation in the 1970s and its popularization in the middle 1980s in the United States, a new era of spinal fixation was ushered in. The first transpedicular fixation systems, such as the AO DCP plate, TSRH(Texas Scottish Rite Hospital), and CD(Cotrel-Dubousset) systems were all manufactured in stainless steel. While stainless steel is an extremely strong and reliable compound, many patients are allergic to stainless steel due to the high nickel content. Also, stainless steel interferes considerably with magnetic Resonance Imaging. The next generation of transpedicular fixation such as the AO Universal Spine System is manufactured in titanium. Titanium eliminates both the allergy and MRI compatibility problems of stainless steel. However, is titanium biomechanically similar to stainless steel in vivo? This is a retrospective look at the use of titanium and stainless steel transpedicular fixation by two surgeons over a minimum follow-up of two years.

Materials & Methods: Ninety-two patients were done with the stainless steel(SS) Universal Spine System. Forty-two were male and 50 were female. Forty-four were smokers and 42 were on workman's compensation. The average age was 50 with a range of 23 to 79. Thirty-four patients had no prior lumbar surgeries. There were 28 single-level, 49 double-level and 15 triple-level fusions. Twenty-four patients also had staged anterior procedures. Autograft was used in 12 patients. An allograft/autograft combination was used in 78 patients and two patients had allograft alone. Patients were treated for varying pathologies including but not limited to failed laminectomy, pseudarthrosis, and spondylolisthesis.

Sixty-two patients were done with the titanium (TAN) Universal Spine System. Thirty-three patients were male and 39 were female. Thirty patients were smokers and 25 were on workman's compensation. Fifteen patients had combined anterior procedures. The average age was 51 and ranged from 25 to 83 years. Thirty-six patients had no prior lumbar surgeries. There were 24 single-level, 32 double-level and six triple-level fusions. Fifty-three patients in this groups received autograft; eight received an allograft/autograft combination; and one received allograft alone. Primary diagnoses were similar to that of the SS group.

Results: The SS group was followed for a minimum of 26 months and an average of three years. The TAN groups was followed for a minimum of 24 months with an average of 27 months. Graft resorption was found in 9(9%) SS patients and 6(9%) TAN patients. Hardware problems were defined as broken screws, loose screws, broken rods, or loss of fixation. In the TAN groups there were 5(5%) hardware problems. Using a chi-square test, there is no significant difference between the two. In the SS group, hardware was removed in 11 patients. Four(4%) were found to be fused and seven(8%) were found to have a pseudarthrosis. In the TAN group, seven patients have had their hardware removed. Six(9.6%) were found to be fused and one had a pseudarthrosis(1.6%). These numbers cannot be compared because they are dependent upon hardware removal and not the entire sample. Also, we believe the sample size to be too small to make any definitive conclusions on fusion rate related to TAN or SS. Blood loss in both groups averaged 215 cc. There was a total of eight dural tears postoperatively from both groups which was repaired without sequelae. Postoperatively, there were two deep wound infections and five superficial wound infections. There was also one U.T.I. and one Seroma postoperatively in the SS group.

Discussion/Conclusion: Based on the minimum two year clinical follow-up in both groups, we find that there is no significant biomechanical difference between titanium and stainless steel pedicle screws of the Universal Spine System in vivo.