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Posterior lumbar interbody cages do not augment segmental biomechanical stability.
J R Dimar1, D J Beck, S D Glassman
1Department of Orthopaedic Surgery, University of Louisville, Kentucky, USA.
American Journal of Orthopedics (Belle Mead, N.J.)
|August 25, 2001
Summary
Posterior threaded interbody cages did not significantly increase lumbar spine stiffness. Supplemental pedicular screw/rod instrumentation, however, did improve stiffness, questioning the stability benefits of cages alone.
Area of Science:
- Orthopedic Surgery
- Spinal Biomechanics
- Neurosurgery
Background:
- Posterior lumbar interbody fusion is a common surgical procedure.
- Threaded interbody cages are frequently used to achieve fusion and provide stability.
- The biomechanical contribution of these cages to overall spinal stability is debated.
Purpose of the Study:
- To evaluate the effect of posterior threaded interbody cages on lumbar spine stiffness.
- To compare the stiffness provided by cages alone versus cages with supplemental instrumentation.
Main Methods:
- Fresh human cadaveric spine specimens (L4-L5) were utilized.
- Testing involved various ranges of motion to assess stiffness.
- Stiffness was measured with and without posterior threaded interbody cages and with supplemental pedicular screw/rod instrumentation.
Main Results:
- Posterior threaded interbody cages did not significantly increase spine stiffness in any tested range of motion.
- Supplemental posterior pedicular screw/rod instrumentation significantly increased spine stiffness.
Conclusions:
- The use of posterior threaded interbody cages as isolated posterior implants may not significantly enhance lumbar spine stability.
- Supplemental posterior instrumentation is crucial for increasing spinal stiffness in this context.