Comparison study of the effect of fusion and non-fusion fixation on the movement of injured lumbar spine

Song Hong-fang; Zhang Wen; Zhang Qiang; Liu Zhi-cheng

doi:10.3969/j.issn.2095-4344.2017.31.008

Abstract：BACKGROUND: Degenerative change in lumbar spine is the natural physiological and pathological process with age increasing, which seriously affects the patients' quality of life. Conventional surgical treatments may bring about some complications. Interspinous stabilization Coflex demonstrates good clinical outcomes, while there is lack of experimental evidence.OBJECTIVE: To investigate the effect of fixation methods on the movement of lumbar vertebrae, and to provide reference for clinical operation from the aspect of biomechanics.METHODS: Five fresh specimens of pig cadaveric lumbar spine were selected and divided into five groups: blank control group (group A), injury group (group B), L3-L4 Coflex fixed (group C), L3-L4 Coflex fixed plus decompression (group D),and L3-L4 intervertebral fusion fixed (group E). The biomechanical performance of the five lumbar specimens was tested in six loading directions of flexion/extension, left/right lateral bending, and left/right axial rotation driven by a robot system.The motion range of the operation segments (L3-L4) and the whole lumbar spine was observed by a multi-directional torque sensor combined with a three-dimensional motion capture system. Finally, the influence of lumber fixation methods on the spinal movement was explored.RESULTS AND CONCLUSION: (1) For the range of three-dimensional angle at the operation segments (L3-L4), it was found that groups C and D were similar to group A, and groups B and E were quite different from group A. (2) Group E could restore the motion range of the injured segments, but the motion angle was much smaller than that in the groups C and D. (3) These results indicate that the motion angle of the injured spine treated with Coflex can restore to the normal state, with long-term stability. For unstable lumbar spine, interspinous Coflex is better than transforaminal lumbar interbody fusion, which can induce similar biomechanical properties to normal lumbar spine after operation.