| 1999 Annual Meeting Poster Exhibits |
Poster Board Number: 192
Lauweryns Philippe, MD, Pellenberg, BELGIUM
Van B Karel, MSc, Heverlee, BELGIUM
J Vandersloten, PhD, Heverlee, BELGIUM
Remi Van Audekercke, PhD, Heverlee, BELGIUM
Vanden B Luc, MD, Pellenberg, BELGIUM
Guy M Fabry, MD, Pellenberg, BELGIUM
Van C Wilfried, MSc, BELGIUM
Pedicle screw fixation has shown to be useful for some specific disorders of the lumbar spine to provide immediate rigid fixation, to reduce the pseudarthrosis rate and to improve the radiological and clinical result. Through appropriate training pedicle screws can be a safe instrumentation technique. However, perforation of the pedicle cortex in up to 40% of cases with pedicle screws has been reported. This sometimes results in temporary or permanent damage to the cauda equina or the nerve roots. Computer assisted surgery and neuronavigation systems are one way to try and avoid these complications. Even with computerassisted surgery malplacement of pedicle screws is still possible and a 4.3% malplacement rate has been reported in the literature. The purpose of this study is to describe a new device which acts as a guide for pedicle screw insertion. The aim is to enhance the safety and accuracy of pedicle screw insertion. Three successive patients planned for a lumbar fusion operation were sent preoperatively for a high resolution CTscan of the vertebrae to be fused (levels L3L4L5, L2L3 and LM4). The CTdata were processed, segmented and transfered to a 3D solid CAD environment that enables a fully parametric design of the drill guide. The design of the drill guide consists of one large contact area on the spinous process and one knifeedge area on the two transverse processes. Planning of the drilling trajectory was performed by the surgeon. The drilling template is produced by stereolithography as rapid prototyping technique. The use of a Zeneca experimental resin which is sterilisable and USP class VI guarantees evaluation during clinical trials. Each template can only be placed one the posterior aspect of one particular vertebra. Seven drilling templates were manufactured for the seven levels involved in the three patients. All seven templates could be applied successfully during the operations with a good stability and unique fit. After drilling through the template, tapping and probing of the drilling trajectory a total of fourteen pedicle screws was inserted as planned preoperatively. Postoperative CTscan showed a good position of all pedicle screws following the pedicle axis and without cortex perforation or malplacement. A complete procedure has been developed from the design onto the surgical application and evaluation of seven drill guides. Fourteen pedicle screws have been implanted succesfully without malplacement or cortex perforation. Personalised templates for pedicle screw insertion can provide additional safety during surgery at a low marginal cost.
Category: Spine
*The FDA has not cleared the drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an "off label" use.)
Hall A of the Anaheim Convention Center
Thursday February 4, 1999 10:00 AM-7:00 PM
The principal exhibitor will be available from 12:00 Noon to 3:00 PM to discuss the exhibit and answer questions regarding the poster.
Cameras may be used in the Poster Exhibit area.
