Oh Yoto, Fujita Koji, Wakabayashi Yoshiaki, Kurosa Yoshiro, Okawa Atsushi
Department of Orthopaedic and Trauma Research, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Orthopaedic and Spinal Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Injury. 2017 Dec;48(12):2736-2743. doi: 10.1016/j.injury.2017.09.023. Epub 2017 Sep 27.
Loading stress due to individual variations in femoral morphology is thought to be strongly associated with the pathogenesis of atypical femoral fracture (AFF). In Japan, studies on AFF regarding pathogenesis in the mid-shaft are well-documented and a key factor in the injury is thought to be femoral shaft bowing deformity. Thus, we developed a CT-based finite element analysis (CT/FEA) model to assess distribution of loading stress in the femoral shaft.
A multicenter prospective study was performed at 12 hospitals in Japan from August 2015 to February 2017. We assembled three study groups-the mid-shaft AFF group (n=12), the subtrochanteric AFF group (n=10), and the control group (n=11)-and analyzed femoral morphology and loading stress in the femoral shaft by nonlinear CT/FEA.
Femoral bowing in the mid-shaft AFF group was significantly greater (lateral bowing, p<0.0001; anterior bowing, p<0.01). Femoral neck-shaft angle in the subtrochanteric AFF group was significantly smaller (p<0.001). On CT/FEA, both the mid-shaft and subtrochanteric AFF group showed maximum tensile stress located adjacent to the fracture site. Quantitatively, there was a correlation between femoral bowing and the ratio of tensile stress, which was calculated between the mid-shaft and subtrochanteric region (lateral bowing, r=0.6373, p<0.0001; anterior bowing, r=-0.5825, p<0.001).
CT/FEA demonstrated that tensile stress by loading stress can cause AFF. The location of AFF injury could be determined by individual stress distribution influenced by femoral bowing and neck-shaft angle.
由于股骨形态的个体差异导致的负荷应力被认为与非典型股骨骨折（AFF）的发病机制密切相关。在日本，关于股骨干发病机制的AFF研究有充分的文献记载，损伤的一个关键因素被认为是股骨干弓形畸形。因此，我们开发了一种基于CT的有限元分析（CT/FEA）模型来评估股骨干中的负荷应力分布。
2015年8月至2017年2月在日本的12家医院进行了一项多中心前瞻性研究。我们组建了三个研究组——股骨干AFF组（n = 12）、转子下AFF组（n = 10）和对照组（n = 11）——并通过非线性CT/FEA分析股骨干的股骨形态和负荷应力。
股骨干AFF组的股骨弓形明显更大（外侧弓形，p < 0.0001；前方弓形，p < 0.01）。转子下AFF组的股骨颈干角明显更小（p < 0.001）。在CT/FEA上，股骨干和转子下AFF组均显示最大拉应力位于骨折部位附近。定量分析显示，股骨弓形与拉应力比值之间存在相关性，该比值是在股骨干和转子下区域之间计算得出的（外侧弓形，r = 0.6373，p < 0.0001；前方弓形，r = -0.5825，p < 0.001）。
CT/FEA表明，负荷应力产生的拉应力可导致AFF。AFF损伤的位置可由受股骨弓形和颈干角影响的个体应力分布决定。
