保留后部韧带复合体结构对腰椎减压融合术后相邻节段生物力学特性的影响

目的比较人体腰椎标本保留后部韧带复合体(posterior ligament complex,PLC)结构在位移及载荷两种不同加载模式下对腰椎减压融合术后相邻节段生物力学特性的影响。方法 6具急性脑死亡新鲜青年男性T12~S2尸体标本,每个标本在位移及载荷加载两种模式下依次完成以下状态的生物力学测试:完整状态、L4~5椎板间大开窗减压固定、L4~5全椎板切除减压固定。通过摄像系统非接触式测量融合相邻节段运动范围(range of motion,ROM),并进行对照研究。结果在位移加载模式下,全椎板切除组屈曲ROM较椎间大开窗组显著增加,而在后伸、侧弯及旋转方面两组无显著性的差别。结论位移和载荷加载模式对腰椎融合术后相邻节段的生物力学影响存在差异性。与保留PLC结构的椎间大开窗减压方式相比,破坏PLC结构的全椎板切除减压方式可以导致相邻节段屈曲ROM显著增加,并提高相邻节段在后伸、侧弯及旋转等运动状态下ROM,其远期出现融合相邻节段失稳的可能性大。

Effects of Preserving Posterior Ligament Complex on Biomechanical Properties of the Adjacent Segments after Lumbar Decompression and Fusion

Objective To compare the effects of preserving the posterior ligament complex (PLC) with torque loading and displacement loading on the biomechanical properties of the adjacent segments after lumbar decompression and fusion. Methods Six fresh male cadaver lumbar specimens of T12-S2 were tested in the sequence of intact, L4-5 laminotomy (preserving the PLC) with fixation and L4-5 laminectomy (destructing the PLC) with fixation, by applying both displacement loading and torque loading, respectively. Ranges-of-motions (ROMs) of the adjacent segments were measured under a noncontact photographic recording system. Results In displacement-loading mode, the flexion ROM in laminectomy group was significantly higher than that in laminotomy group, and no obvious ROM differences were found in the laminectomy and laminotomy groups under extension, lateral bending, and rotation movement. Conclusions Torque loading and displacement loading have different biomechanical effects on the adjacent segments after lumbar decompression and fusion. Compared with the laminotomy method, in which the PLC is preserved, the laminectomy method in which PLC structures are damaged can obviously lead to an increment of flexion ROMs at the adjacent segments, and also increase the ROMs of the adjacent segments under extension, lateral bending, and rotation movements, which might increase the risk of further instability of the fused adjacent segments.