骨水泥不同分布对骨质疏松性椎体压缩性骨折的生物力学影响:三维有限元分析

目的:在骨质疏松性椎体压缩性骨折（OVCFs）椎体成形术（PVP）中，病椎内骨水泥分布不充分、不对称，将影响手术效果及远期症状。本文研究椎体成形术中骨水泥在椎体内分布情况对术后病椎的应力影响。方法:利用志愿者椎体CT数据，建立T12~L2椎体有限元模型。模拟L1椎体OVCFs，行PVP。向L1椎体内注入骨水泥柱，骨水泥形成3组分布模式（骨水泥分布不充分组、分布充分组和分布不对称组，其中分布不对称组包括骨水泥偏上分布和偏下分布）。研究不同方向运动对术后L1椎体的生物力学影响。结果:（1）与骨质疏松的L1椎体应力相比，术后L1椎体松质骨中最大应力的分布主要集中于骨水泥周围的松质骨，而皮质骨中最大应力的分布没有变化。（2）与骨水泥分布充分组相比，不充分组L1椎体的松质骨和皮质骨的最大应力和最大位移均显著增加，而不对称组中松质骨的最大应力显著增加。（3）在不同方向的载荷条件下都能得到相似的结果。结论:（1）在OVCFs的PVP中，病椎骨水泥分布不充分会引起术后该椎体最大位移明显增加，导致术后疼痛未缓解。（2）病椎骨水泥分布不充分和分布不对称会引起术后病椎皮质骨及松质骨的最大应力明显增加，所以容易导致术后病椎的再次骨折。

Biomechanical effects of different distributions of bone cement on osteoporotic vertebral compression fractures: a three-dimensional finite element analysis

Abstract: Objective In percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs), the inadequate and asymmetrical distributions of bone cement in the affected vertebra will affect surgical effect and long-term symptoms. The effects of the distribution of bone cement in the vertebra on the stress of the affected vertebra after PVP are analyzed in the study. Methods The finite element model of T12-L2 vertebral body was established using the CT data of the vertebral body of a volunteer. The OVCFs of L1 vertebral body was simulated, and then PVP was carried out. The bone cement column was injected into L1 vertebral body, and there are 3 distribution patterns of bone cement, namely inadequate distribution group, well-distribution group, and asymmetrical distribution (including the upper and lower distributions) group. The biomechanical effects of movements in different directions on L1 vertebral body after surgery were analyzed. Results Compared with the stress of osteoporotic L1 vertebral body, the maximum stress of postoperative L1 vertebral cancellous bone was mainly concentrated at the cancellous bone around bone cement, while the distribution of maximum stress of cortical bone remain unchanged. Compared with those in well-distribution group, the maximum stress and maximum displacement of L1 vertebral cancellous bone and cortical bone in inadequate distribution group were significantly increased, while the maximum stress of cancellous bone in the asymmetrical distribution group was significantly increased. Similar results could be obtained under all loading conditions in different directions. Conclusion In PVP for OVCFs, inadequate distribution of vertebral cement will lead to significantly increased maximum displacement of the vertebral body after surgery, resulting in unrelieved postoperative pain. Inadequate and asymmetrical distributions of the diseased vertebrae cement will significantly increase the maximum stress of the diseased vertebral cortical bone and cancellous bone after surgery, so it is easy to cause the re-fracture of the diseased vertebra after surgery.