一种新型腰椎峡部裂修复装置生物力学性能的三维有限元分析

A three-dimensional finite element analysis of the biomechanical properties of a new lumbar spondylolysis repair device

目的:应用有限元分析的方法,研究一种新型腰椎峡部裂修复装置的生物力学性能。方法:采集一例健康志愿者腰椎CT数据进行三维重建,构建并验证L3~S1脊柱节段的非线性有限元模型(A),在此基础上,分别建立L5峡部裂模型(B)、椎弓根螺钉U形棒固定模型(C)、新型腰椎峡部裂修复装置固定模型(D)。将4种模型的S1椎体下表面的自由度进行约束,在L3椎体上表面分别施加500N的轴向压缩力和10N·m的力矩载荷来模拟腰椎前屈、后伸、左右侧弯及左右旋转6种运动状态,比较各有限元模型在不同运动状态下的腰椎活动度(range of motion,ROM)、L5棘突根部应力和峡部的轴向压力。结果:与相关文献数据比较,模型A在L4~L5,L5~S1节段的ROM与既往研究结果相近,证明本模型有效。在六种运动状态下,模型C和模型D的ROM比模型B分别下降了16.46%~55.98%、17.48%~40.65%;模型D的ROM比模型C平均大0.44°。相较于模型C,模型D在前屈、后伸、左右侧弯及左右旋转时,L5棘突的最大应力分别减少了12.71%、54.95%、58.46%、53.97%、46.91%及72.34%,有效降低棘突骨折的风险;腰椎峡部的轴向压力分别增加了236.51%、282.51%、216.98%、231.47%、294.03%及138.91%,可以更高效地促进骨折愈合。结论:新型腰椎峡部裂修复装置在保留腰椎活动度的同时,可以较好地重建腰椎峡部裂的即刻稳定性;相较于椎弓根螺钉U形棒固定装置,可以提供足够的力学稳定性,且降低棘突骨折的风险。

Objectives:To evaluate the biomechanical properties of a new lumbar spondylolysis repair device by three-dimensional finite element analysis.Methods:A nonlinear finite element model of L3-S1 segment(A)was constructed on the 3D reconstruction of the lumbar CT data extracted from a healthy volunteer and was verified.Based on this,L5 spondylolysis model(B),pedicle screw-U-shaped rod fixation model(C),and the new lumbar spondylolysis repair device model(D)were established.The freedom of the lower surface of S1 vertebral body of the four models were constrained.The axial compression forces of 500N and moment loads of 10N·m were applied to the upper surface of L3 vertebral body to simulate six motion states of lumbar flexion,extension,left and right bending and rotation.The range of motion(ROM)of lumbar spine,the stress of L5 spinous process root,and axial pressure of isthmus were compared between models under different motion states.Results:The ROM of model A at L4-L5 and L5-S1 segments were similar to those reported previously,demonstrating the effectiveness of this model.At all motion states,the ROMs of models C and D decreased by 16.46%-55.98% and 17.48%-40.65%than model B,respectively;the average ROM of model D was 0.44°larger than that of model C.Comparing with model C,the maximum stresses of the L5 spinous process of the model D decreased by 12.71%,54.95%,58.46%,53.97%,46.91%,and 72.34%,respectively,which can reduce the risks of L5 spinous process fracture;and the axial pressures of lumbar isthmus increased by 236.51%,282.51%,216.98%,231.47%,294.03%,and 138.91%,respectively,which may accelerate bone healing more effectively.Conclusions:The new lumbar spondylolysis repair device could better stabilize lumbar spondylolysis while preserving the ROM of lumbar spine.As compared with pedicle screw-U-shaped rod,the new lumbar spondylolysis repair device might provide sufficient mechanical stability and reduce the risk of spinous process fracture.