大龄髋脱位儿童股骨颈前倾角变化与骨骺应力的有限元分析研究

目的运用有限元分析方法,对正常及发育性髋关节发育不良(DDH)儿童股骨头近端骨骺生长板同承力情况下横断面的应力进行研究,为股骨近端截骨矫形手术提供理论依据。方法按照Tonnis分型选取40例DDH大龄儿童,其中男性11例,女性29例;年龄8～12岁,平均年龄10.14岁。分为半脱位及全脱位组。20例非DDH儿童作为正常对照组,其中男性11例,女性9例;年龄8～12岁,平均年龄10.10岁。通过二维CT技术测定各组股骨颈前倾角,通过有限元分析软件分析股骨头近端骨骺生长板在横断面上的应力情况。结果正常对照组股骨头近端骨骺生长板横断面上前内侧及后外侧的切应力和静压力相当。半脱位组及全脱位组股骨头近端骨骺生长板横断面上前内侧静压力大于后外侧,而前内侧的切应力小于后外侧。股骨颈前倾角与前后两侧静压力差呈正相关,与前后两侧切应力差呈负相关。结论 DDH大龄儿童的股骨颈前倾角随生长发育而增大。传统的股骨近端旋转截骨术在纠正发育性髋脱位儿童股骨骨骺异常应力,保证正常的头臼关系中有重要的临床意义。

Change of femoral neck anteversion of hip dysplasia in older children and finite element analysis of epiphyseal stress

Objective To analyze the stress differentiation and morphological changes of proximal femoral growth plate in axial plane under different loads in normal and developmental dislocation of hip（DDH） children by finite element analysis,and provide rationality of femoral derotational surgery in children.Methods A total of 40 DDH older children were enrolled,male 11,female 29,aged 8-12 years old,mean aged 10.14 years old,according to Tonnis category which were divided into subluxation group and dislocation group.Twenty normal children were enrolled as contrast,male 11,female 9,aged 8-12 years old,mean age 10.10 years old.Each of them was performed CT scan and measured anteversion angle in 2-dimensional CT images.The contact force on proximal femur was simulated to analyze the stress differentiation and morphological change of proximal femoral growth front in axial plane with ANSYS software.Results Under normal-loading conditions,there was almost equivalent hydrostatic tension and shear stress on anteriolateral portion of the growth region of proximal femurs as to that on posteriomedial sides.With DDH-loading conditions,there was higher hydrostatic tension on anteriolateral sides than that on posteriomedial sides,shear stress reversely.The results also showed anteversion angle was positively correlated with hydrostatic tension difference and negatively correlated with shear stress difference on anterior and posterior sides of growth front.Conclusion It is demonstrated that abnormal stress distribution on hip joints make an important role in pathological changes of children＇s hip,under normal-loading conditions there is almost equivalent hydrostatic tension and shear stress on anteriolateral portion of growth region of proximal femurs as to that on the posteriomedial sides,which suggested that the anterversion angle of normal older children keeps a stable location with growth.The traditional femoral derotational osteotomy is still a reasonable strategy in correcting the stress discrepancy and keeping the normal acetabular-head relationship in DDH children.