步态周期中髋关节软骨应力分布对弧形髋臼周围截骨手术的影响

Stress Distributions of Hip Cartilage During Gait Cycle and its Effects in Curved Periacetabular Osteotomy

目的研究在完整步态周期受力环境下髋关节周围软骨的应力分布情况,探求弧形髋臼周围截骨术(curved periacetabular osteotomy,CPO)术中所截骨块的最佳矫正角度,为临床手术提供理论依据。方法利用CT扫描获取1名髋关节发育不良(development dysplasia of hip,DDH)患者和1名健康志愿者骨盆及股骨近端DICOM数据,构建三维有限元模型。采用划分蒙罩的方法区分皮质骨和松质骨,并为有限元模型赋予材料属性。对DDH模型模拟CPO,调整外侧中心边缘角(lateral center edge angle,LCEA)和前方中心边缘角(anterior center edge angle,ACEA),共得到100个不同的术后模型。根据完整步态周期中的髋关节受力情况为模型分别施加载荷,分析对比术前、术后和正常髋臼软骨的受力变化。结果DDH模型模拟术后髋臼软骨在完整步态周期中脚跟落地相、开始单腿支撑相、单腿支撑中期相、单腿支撑结束相、双腿支撑相的最小接触应力峰值分别为5.273、6.128、7.463、6.347、6.582 MPa,分别比术前减少了2.159、2.724、2.249、2.164、2.119 MPa;术后头臼接触面积较术前明显增加,但仍小于正常志愿者。结论利用有限元方法可以得到LCEA和ACEA的最佳矫正角度,对不同患者模拟CPO手术对提高手术精准度和手术效率具有重要意义。

Objective To study stress distributions of the cartilage around the hip joint in stress environment of complete gait cycle,and explore the optimal correction angle of bone block in curved periacetabular osteotomy(CPO),so as to provide theoretical references for clinical operation.Methods Based on CT scans from a healthy volunteer and a patient with development dysplasia of hip(DDH),the three-dimensional(3D)model including pelvis and proximal femur was reconstructed.The cortical bone and cancellous bone were distinguished by dividing the masks,and the material attributes were assigned to the finite element model.A total of 100 different postoperative models were obtained by simulating CPO in DDH model,by adjusting lateral center edge angle(LCEA)and anterior center edge angle(ACEA).According to hip joint stresses in complete gait cycle,the model was loaded respectively,and stress changes of normal,preoperative and postoperative acetabular cartilage were analyzed and compared.Results The minimum peak contact stresses of acetabular cartilage of DDH patient at heel landing phase,start phase of single leg support,mid phase of single leg support,end phase of single leg support and double support phase after simulated CPO operation were 5.273,6.128,7.463,6.347,6.582 MPa,which were decreased by 2.159,2.724,2.249,2.164,2.119 MPa,respectively,compared with those before operation.The contact area between femoral head and acetabulum was significantly increased after operation,but it was still smaller than that of normal volunteers.Conclusions The optimal correction angle of LCEA and ACEA can be obtained by using finite element method,and the simulation of CPO surgery on different patients is of great significance to improve surgical accuracy and efficiency.