Author: Rachit Parikh

Publisher:

Published: 2010

Total Pages: 119

ISBN-13:

Spinal stenosis is a degenerative process, caused by progressive narrowing of the lumbar spinal canal and neural foramen, leading to a constriction of the nerve roots of the cauda equina. Currently, facetectomy and laminectomy combined with fusion are the standard methods of decompression for the degenerative lumbar spinal stenosis with resultant alteration in established inter-relationships between various vertebral column components. However due to myriad of degenerative complications at the fused level and adjacent level degeneration, numerous new posterior dynamic stabilization systems have been developed. The objective of this biomechanical study was to investigate the influence of different grades of factectomy, spinal decompression and laminectomy procedures in conjunction with various dynamic stabilization implants viz. Dynesys, In-Space spacer and Stabilimax. A validated, 3-D, nonlinear finite element model of the intact L3-S1 lumbar spine was used to evaluate the biomechanics of these devices. The load control protocol was used to evaluate these devices. Various biomechanically relevant parameters like range of motion, facet loading, disc stresses were evaluated. An in vitro study was also performed comparing Dynesys with novel PEEK Rod dynamic stabilization system for decompression surgery with discectomy. The finite element results showed that the Dynesys and Stabilimax systems were capable of stabilizing the decompression surgery in flexion, extension and lateral bending. The In-Space spacer effectively reduced motion in extension and did not interfere with motion in other loading modes at the implanted level. All the systems were capable of loading through the intervertebral disc. Results also showed that after complete facetectomy the systems did not restore stability in axial rotation. Further a cadaveric study was to done to compare the Dynesys stabilization system with that of a novel PEEK rod pedicle screw stabilization system after simulating decompression surgery. The biomechanical comparison of monosegmental fixation on L4-L5 and bi-segmental fixation of L3-L5 as topping off procedure with fusion were done for this study. The predicted range of motion for the PEEK rod stabilization system was consistent with the Dynesys for monosegmental fixation.