A technique to evaluate an internal spinal device by use of the Selspot system: an application to Luque closed loop.

A technique to study the effects of spinal injury and stabilization in terms of load-deformation behavior is described. Fresh human cadaveric ligamentous spine segments (T12-sacrum) were potted and clinically relevant loads applied through the loading frame attached to the topmost vertebra of the specimen. The resulting three-dimensional motion responses of each vertebra for the normal specimen were recorded with the Selspot II System. The specimen was injured at the L4-5 motion segment to represent a typical surgical decompression used in treating patients with spinal stenosis and tested again. The decompressed (or injured) motion segment was stabilized with a Luque closed-loop (Luque rectangle) system before repeating the test protocol. The data of these tests indicate that the injury (surgical decompression) at the L4-5 motion segment leads to a significant increase in motion--in flexion, extension, and axial modes--indicating the possible necessity for stabilization of the injured segment. The closed-loop system reduces the motion at the injured level, with respect to normal specimen behavior, by 35%. Therefore, the system does not provide complete immobilization (100% reduction with respect to normal specimen behavior). The stabilizing effects of the closed loop in lateral bending are not significant and are marginal in axial motion. The motion across the L3-4 motion segment in flexion increases significantly after stabilization. The clinical implications and the need for further studies are also discussed.