空心拉力螺钉治疗腰椎峡部裂的三维有限元分析

Three-dimensional finite element analysis of the treatment of lumbar spondylolysis with cannulated lag screw

背景:空心拉力螺钉技术治疗峡部裂有很多优势,但依然存在内固定的断裂、松动的风险。目的:通过三维有限元软件建立L-S正常模型、峡部裂模型及空心拉力螺钉治疗腰椎峡部裂模型,分析空心拉力螺钉治疗腰椎峡部裂的生物力学稳定性。方法:选择1名男性健康青年军人志愿者,对志愿者腰椎、骶椎进行三维CT扫描,获取影像学数据并保存为Dicom格式。将CT数据导入Mimics research 21.0软件初步建立几何模型,并进行偏差分析,将所得模型以STEP格式输出;再导入Solidworks 21.0软件分别建立L-S节段正常、L双侧峡部裂、空心拉力螺钉治疗峡部裂3组模型,分别用A,B,C表示,比较轴向压缩、前屈、后伸、左侧弯、左旋转5种工况下3组模型的生物力学特点。结果与结论:①相比于A,C模型,B模型在轴向压缩、前屈、后伸、左侧弯、左旋转5种工况下的整体最大位移均为最大,而A,C整体最大位移相差不明显;②C模型去除内固定之后,最大应力趋势与A模型相近,而B模型在左侧弯及左旋转时应力明显高于A,C模型;③3组模型的整体最大转角表明,B模型在5种工况下的最大转角明显大于A,C模型,A,C模型相似;3组模型L椎体的活动度变化不明显;而B模型L椎体的活动度明显高于A,C模型,在左侧旋转及左侧弯时更明显;④结果说明,脊柱生理运动状态下,空心拉力螺钉治疗腰椎峡部裂模型的变化趋势同正常模型,可获得良好的生物力学稳定性,保留了脊柱的正常力学特性,但应避免术后即刻过度的后伸及旋转。

BACKGROUND:The cannulated lag screw technique has many advantages in the treatment of spondylolysis,but there is still the risk of fra cture and loosening of the internal fixation.OBJECTIVE:To analyze the biomechanical stability of cannulated lag screw treatment of spondylolysis by establishing L4-S normal model,spondylolysis model and cannulated lag screw treatment model of spondylolysis thro ugh three-dimensional finite element software.METHODS:One male healthy young soldier volunteer was selected.3 D CT scan was performed on the volunteer s lumbar spine and sacral spine.The imaging data were obtained and saved in Dicom format.CT data were imported into Mimics research 21.0 software to initially establish a geometric model,and deviation analysis was carried out.The obtained model was output in STEP format.Three groups of models of normal L-S segment,Lbilateral isthmus and cannulated lag screw in the treatment of spondylolysis were established after imported into Solidworks 21.0 software.They were represented by A,B and C respectively.The biomechanical characte ristics of the three groups of models were compared under five motion states,such as axial compression,flexion,extension,left bending,and left rotation.RESULTS AND CONCLUSION:(1) Compared with models A and C,model B had the largest ove rall maximum displacement under the five working conditions of axial compression,flexion,extension,left bending,and left rotation.Howeve r,the overall maximum displacement of models A and C was not significantly different.(2) After removing the internal fixation in the model C,the maximum stress trend was similar to the model A.The stress of the model B was significantly higher than that of the models A and C during left bending and left rotation.(3) The overall maximum rotation angle of the three groups of models showed that the maximum rotation angle of the model B under the five working conditions was significantly larger than that of the models A and C.The models A and C were similar.The range of motion of the Lvertebral body in the three groups did not change significantly.The range of motion of the Lvertebral body in the model B was significantly higher than that in the models A and C,and it was more obvious in the left rotation and left bending.(4) These findings indicate that under the condition of physiological movement of the spin e,the change trend of cannulated lag screw in the treatment of lumbar spondylolysis model is the same as that of normal model,which obtains good biomechanical stability and retains the normal mechanical characte ristics of the spin e,but excessive extension and rotation should be avoided immediately after operation.