Diedrich, Oliver and Kraft, C. N. and Luering, Christian and Perlick, Lars and Pennekamp, P. H. (2005) Stability of different interbody fusion techniques after pedicle screw loosening. ZEITSCHRIFT FUR ORTHOPADIE UND IHRE GRENZGEBIETE, 143 (2). pp. 179-185. ISSN 0044-3220,
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Introduction: In spinal surgery, postoperative failure of pedicle screw instrumentation due to loosening of the implant at the bone-screw interface is a clinically relevant problem. While there are numerous biomechanical studies dealing with stability after internal fixation, little is known about the remaining segmental stability after pedicle screw loosening. We hypothesize that, in cases of implant loosening, the remaining stability is dependent on whether the segment received an isolated pedicle screw instrumentation or a 360 degrees instrumentation. Methods: Motion analysis was performed under static, damage-free, sagittal strain (preload 100 N) on intact (controls) and posterior monosegmental L5/6 destabilized lumbar spines of sheep. Spine preparations underwent a flectional torque. Changes of spinal profile were radiographically documented, digitalized and then evaluated. Primary insertion of the conical pedicle screws was performed with a torque of 1.4 Nm. Pedicle screw loosening was simulated by turning the inserted screw back either 180 degrees or 540 degrees. Specimens instrumented with screws of differing diameters (5.5mm and 6.7mm) as well as non-instrumented pedicles were also comp red. Results: Independent of the type of instrumentation, we found that a loosening of pedicle screws increased remaining segmental motion. In maximal flexion (20 degrees) and loosening of pedicle screws by 540 degrees, we found a statistically significant increase of remaining segmental motion with sole pedicle instrumentation (-3.1 degrees) in contrast to 360 degrees instrumentation (-1.6 degrees). For extension, a significant discrepancy between the two stabilization methods could not be shown. In cases where screws were firmly inserted, there was no advantage of using pedicle screws with an increased diameter of 6.7 mm. Independent of the type of fixation method, 5.5 mm screws that were inserted in widened pedicles showed a marked decrease of primary segmental stability. Conclusion: This study suggests that, concerning the remaining stability, 360 degrees instrumentation is superior in cases where pedicle screw loosening has occurred. The screw diameter plays an only subordinate role in primary segmental stability when the pedicle screws are inserted firmly.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | LUMBAR SPINE; INSERTIONAL TORQUE; FIXATION; BONE; STRENGTHS; DENSITY; DESIGN; MOTION; CAGE; pedicle screw loosening; lumbar spine; spinal instrumentation; 360 degree fusion; biomechanics |
| Subjects: | 600 Technology > 610 Medical sciences Medicine |
| Divisions: | Medicine > Lehrstuhl für Orthopädie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 28 May 2021 08:25 |
| Last Modified: | 28 May 2021 08:25 |
| URI: | https://pred.uni-regensburg.de/id/eprint/36474 |
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