Prospective Design Delineation And In Vitro Evaluation Of A New Dynamic Stabilization System And Correlated Clinical Research

Part I Prospective design and stability evaluation of a new dynamic stabilization system in lumbar spine and the effects on adjacent segmentsObjective:To design and determine the magnitude of stabilization and the effect on the adjacent segment of a new dynamic stabilization system. Methods:1. Six lumbar cadaver spines were tested for ROM of each segment.2. New dynamic system consists of titanium-alloy rods, cables and springs. The system was designed for 10°motion in flextion-extension and lateral bending,5°for rotation. 3. Six lumbar cadaver spines were used for testing. A controlled defect was created in the L3-4 segment. The ROM for the bridged and the adjacent segments were determined. The end plate stress of both stabilization methods on the superior adjacent segments were measured at the same time. Results:Both the dynamic system and rigid fixator reduced the ROM and NZ below the magnitude of the intact spine for lateral bending, flexion and extension. In axial rotation the ROM for the dynamic system was in the range of the intact spine, while the rigid fixator showed a decreased ROM. For adjacent segments, no significant differences of ROM were found among intact, dynamic and rigid fixation systems. Conclusion:In the lumbar cadaver spines after defect was created in the L3-4 segment, restoration of stability with the new dynamic system is possible in flexion, extension, right and left lateral bending, and in axial rotation. The ROM and NZ of the adjacent segments were not affected by the instrumentation of the bridged segment. Part II Stability evaluation of the new dynamic stabilization system combined with transpedicular intracorporeal bone grafting for thoracolumbar burst fractures and correlated clinical researchObjective:To evaluate the fate of injuried discs for acute thoracolumbar burst fractures. And to determine the magnitude of stabilization of the new dynamic system combined with transpedicular intracorporeal bone grafting. Methods:1. Patients with acute thoracolumbar fractures were randomized selected, who had been operatively treated with short segment posterior instrumentation supplemented with transpedicular intracorporeal bone grafting. A grading system for lumbar disc degeneration was used. The superior-inferior endplate angle and vertebral body angle had been assessed at follow up.2. Six thoracolumbar cadaver spines were used for testing. A controlled L2 burst fracture was created. The L1-3 motions were determined. Reaults:1. For alteration of superior-inferior endplate angle and the degeneration rate of discs, the deference between two groups were significant.2. In extension, flexion and lateral bending, the dynamic fixator stabilized the segment to a ROM below the magnitude of the intact spine, but showed an increased ROM of axial rotation (P< 0.05) compared with the intact spine. Conclusion:1. The injuried discs were liable to degeneration.2. Restoration of stability with the newly developed dynamic system combined with transpedicular intracorporeal bone grafting is possible in flexion, extension, right and left lateral bending for thoracolumbar burst fracture but for axial rotation.