经Coflex固定下腰椎不同节段后的椎间盘

目的 ：模拟临床术式,经Coflex分别固定下腰椎L4,5、L5S1节段,分析其手术节段及邻近节段椎间盘生物力学的差异性。方法：建立下腰椎及Coflex应用于下腰椎的3组有限元模型（完整下腰椎、Coflex固定腰椎L4,5及L5S1节段）。根据脊柱三柱加载理论,模拟下腰椎直立、前屈和后伸3种生理状态下,比较分析纤维环不同区域的应力大小、椎间隙背侧高度变化及髓核内压水平。结果：在直立和后伸工况下,Coflex分别植入L4,5、L5S1节段,均能减少其手术节段纤维环后区应力,限制椎间隙高度变化,并且降低髓核的应力水平。在后伸工况下,Coflex植入L4,5节段可降低L5S1节段的椎间盘应力水平,但Coflex植入L5S1节段不改变L4,5节段椎间盘应力大小。结论：Coflex固定L4,5、L5S1节段均能减少本手术节段椎间盘负载。另外,Coflex固定L4,5节段,起到降低L5S1节段椎间盘负载的生物力学效果。

Biomechanical characteristics analysis on discs with Coflex fixation on the different segments of lower lumbar spine

Objective: To investigate the biomechanical differences between the surgery and adjacent segments of intervertebral discs in the lower lumbar spine,which were implanted with Coflex into the segments of L_4,5 and L₅S₁,respectively.Methods: Three finite-element models (the model of the intact lower lumbar sacrum,the L_4,5 and L₅S₁ segments implanted by Coflex) were developed,respectively. According to the spinal three-column loading theory,three models were forced by the physiological loads of upright standing,flexion and extension. The stress of the different areas of the disc annulus,the changes of intervertebral dorsal height and the degree of nucleus pulposus pressure were compared and analyzed.Results: Coflex implanted into the L_4,5 and L₅S₁ segments in compression and extension could both decrease the stress of the posterior area of intervertebral disc in the surgery segment,resist the changes of the intervertebral disc dorsal height and reduce the perssure of nucleus pulposus. Furthermore,the stress of the L₅S₁ segment decreased when Coflex fixed the L_4,5 segment in extension. However,when Coflex fixed the L₅S₁ segment,the stress of L_4,5 segment had no significant changes.Conclusion: Coflex fixing the L_4,5 and L₅S₁ segments can effectively decrease the stress of the surgery segmental discs,respectively. Furthermore,Coflex fixing L_4,5 segment may play a biomechanical role in reducing the stress of L₅S₁ segment.