Different Iumbar Fusion Methods For Management Of Instability Of Lower Lumbar Spine: A Biomechanical Study In Vitro

In order to investigate different lumbar fusion methods and fatigue loading in the management of instability of lower lumbar spine, we observed and compared the range of motion (ROM) of various segments under different conditions biomechanically in vitro. The results indicated that the spine fixed by CD implant had a good stability instantly, but presented an unstable trend after fatigue loading test. The spine fixed by CD implant combined with intervertebral bone graft (CD-graft) or TFC ( CD-TFC ) yielded high values for stiffness in flexion-extension, lateral bending and axial rotation compared with the intact lumbar spine. Even after fatigue loading test, both CD-graft and CD-TFC had still kept a satisfied stability. Stabilized by CD, ROM of the fixed segments had a distinct difference before and after the installation of cross-link device (CLD). The ROM of the upper adjacent segment after the spinalfusion increased significantly in all six motions, and the ROM of the lower adjacent segment increased distinctly while rotated but there were no obvious differences in flexion-extension and lateral bending compared with the intact lumbar spine.The reduction, fixation and the spinal fusion against the spondylolisthesis and instability of the spine could achieve the demand of the stability biomechanically, and the appliance of the segmental transpedicle screw fixations increase the effect of the spondylodesis. But the spine with segmental fixations lacks solid supports of the superior column. To deal with the cases of the obvious spondylolisthesis or severe instability of the lumbar, we should do our best to choose posterior lumbar interbody fusion (PLIF). Furthermore, the choice of the intervertebral inserts should change according to the practice, and we should not pursue latest types of implantation. The follow-up curative effect of Cage is still not unclear. The ROM of the adjacent segment increases which accelerates the degeneration after the fusion, especially at the time when solid metal internal fixations are used. CLD can significantly increase the stiffness of internal fixations and make the lumbar more stable...