采用数字人模型探究DDH闭合复位后股骨头缺血坏死的发生机制

Pathogenetic mechanism of avascular necrosis after closed reduction of DDH:a research using digital human model

[目的]利用数字人三维模型结合有限元技术,对髋关节内部生物力学情况进行分析,探究髋关节发育不良(DDH)闭合复位后发生股骨头缺血坏死(AVN)的可能机制。[方法]基于中国女婴1号数字人数据集,重建中国女婴髋关节三维模型,模拟髋关节屈曲外展运动过程,通过三维有限元技术观察髋臼和股骨头之间挤压力的大小和其空间位置改变情况。[结果]该三维模型清晰的反映了髋关节内部组成和空间结构;有限元模型从髋关节伸直位至屈髋90°外展60°过程中,髋臼侧所受挤压点呈现自髋臼中心处向髋臼前下方再向髋臼下方"U"形软骨凹的空间转移过程,股骨头表面所受挤压点呈现出从上到下再到上,从集中到分散再到集中的空间变化过程;股骨头表面压力峰值在屈髋90°、外展50°后进入更高的压力范围。[结论]中国女婴1号数字人髋关节三维模型具有代表性,有助于了解新生儿髋关节的内部结构;DDH闭合复位后AVN的发生机制可能与该屈髋外展位下头臼间的接触挤压压迫了通过该点的股骨头供血血管有关,其与股骨头表面升高的挤压力,共同导致了股骨头缺血坏死的发生。

[Objective] To investigate the possible mechanism of avascular necrosis （AVN） after closed reduction of developmental dysplasia of the hip （DDH） by a 3D reconstructed digital hip model. [Method] A 3D digital model of hip joint was reconstructed based on Chinese digital human girl NO. 1 （CDH-G1） . Data was set and mesh into finite element software. Then, during simulatiing process of hip flexion and abduction movement, the stress value and its spatial position between acetabulum and femoral head surfaces was detected. [Result] The model clearly demonstrated the components and internal structure of the neonate hip joint. In the process from hip extension to 90° flexion and 60° abduction position, the stress loading on acetabular surface located in the center of acetabular iliac region at first, then shifted to the anteroinferior part of acetabulum,and finally to the U-shaped cartilage notch. The stress load- ing on femoral head surface also shifted from superior to inferior and then back to superior part of femoral head, in other words, its distribution shifted from concentrated to scattered and then back to concentrated. The maximum stress on femoral head proved at 90° of flexion and 50° of abduction of the hip. [ Conclusion] The reeonstructed 3D digital hip model is representative of Chinese female infants and can help to understand the internal structure of neonate hip joint. The mechanics of AVN after closed reduction of DDH might be related to the compression of blood vessels that supply femoral head, which is caused by extrusion between acetabular and femoral head surfaces as hip flexion and abduction increased. The rising stress on femoral head surface combined with vessel compression lead to oecurrence of AVN.