有限元分析显微镜下不同比例髓核摘除后的腰椎力学特征

Lumbar biomechanical characteristics after microsurgical lumbar discectomy with different proportions of nucleus pulposus:finite element analysis

背景:国内腰椎髓核摘除后有限元模型多是建立在正常椎体模型的基础上,去除了完整的髓核组织,但是没有考虑到实际手术过程中髓核只是部分摘除以及椎板开窗同时对脊柱力学产生的影响。目的:精确建立腰椎L4/5节段显微镜辅助下不同比例髓核摘除模型,比较髓核摘除前后的力学特征。方法:选择1例腰间盘突出症患者,获取术前CT数据构建有限元模型并验证其有效性,再获取术后CT数据并构建显微镜辅助下椎板单纯开窗、开窗+髓核摘除1/3及开窗+髓核全部摘除共4种模型,给予特定加载条件下比较其在前屈、后伸、左右侧弯、左右旋转6种载荷下的生物力学特征。结果与结论:精确构建了显微镜下不同比例髓核摘除后腰椎的有限元模型。通过力学特征分析得知,显微镜下不同比例髓核摘除后腰椎在屈伸状态下的稳定性明显降低,应力趋向关节突、椎板峡部等后柱结构集中,在屈伸及椎板开窗对侧弯曲活动时影响较大,髓核摘除程度与其影响有关。

BACKGROUND：Most finite element models of microsurgical lumbar discectomy are built on the basis of normal vertebral bodies in China to remove the complete nucleus pulposus tissue. However, it did not consider the only part of nucleus pulposus removal in the process of actual operation and the impact of vertebral lamina fenestration on spinal mechanics at the same time. OBJECTIVE：To establish precisely three-dimensional finite element model （L4/5） to compare biomechanical characteristics caused by the different proportions of discectomy under a microscope. METHODS：One patient with lumbar intervertebral disc herniation was selected. Preoperative CT data were used to construct finite element models, and its effectiveness was validated. Postoperative CT data were col ected. Degeneration model, vertebral lamina fenestration model, microsurgical lumbar discectomy model （removal of a third of nucleus pulposus） and al nucleus pulposus resection model were constructed. Under specific loading conditions, biomechanical characteristics were compared in the flexion-extension, lateral bending, and axial rotation conditions. RESULTS AND CONCLUSION：Finite element models of lumbar vertebrae were accurately established after discectomy at various proportions under the microscope. Mechanical property analysis demonstrated that after microsurgical lumbar discectomy and removing different proportions of nucleus pulposus, under flexion-extension condition, the end max-stress distributed in the isthmus and the superior articular facet, besides the stability of the lumbar spine, was reduced. This change on the opposite direction of vertebral lamina fenestration was most obvious when lateral-bending and backward extension condition. The proportion of nucleus pulposus removal was associated with its effects.