Injury Biomechanics and Aging Laboratory, Department of Kinesiology and Health Sciences, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 Canada.
Centre for Community, Clinical and Applied Research Excellence, Department of Kinesiology and Health Sciences, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 Canada.
J Biomech. 2022 Aug;141:111192. doi: 10.1016/j.jbiomech.2022.111192. Epub 2022 Jun 11.
Metrics of femur geometry and body composition have been linked to clinical hip fracture risk. Mechanistic explanations for these relationships have generally focused on femur strength; however, impact loading also modulates fracture risk. We evaluated the potential effects of femur geometry and body composition on femoral neck stresses during lateral impacts. Fifteen female volunteers completed low-energy sideways falls on to the hip. Additionally, participants completed ultrasound and dual-energy x-ray absorptiometry imaging to characterize trochanteric soft tissue thickness (TSTT) over the hip and six metrics of femur geometry, respectively. Subject-specific beam models were developed and utilized to calculate peak femoral neck stress (σ), utilizing experimental impact dynamics. Except for femoral neck axis length, all metrics of femur geometry were positively correlated with σ (all p < 0.05). Larger/more prominent proximal femurs were associated with increased force over the proximal femur, whereas a wider neck-shaft angle was associated with greater stress generation independent of force (all p < 0.05). Body mass index (BMI) and TSTT were negatively correlated with σ (both p < 0.05). Despite strong correlations, these metrics of body composition appear to influence femoral neck stresses through different mechanisms. Increased TSTT was associated with reduced force over the proximal femur, whereas increased BMI was associated with greater resistance to stress generation (both p < 0.05). This study provided novel insights into the mechanistic pathways through which femur geometry and body composition may modulate hip fracture risk. Our findings complement clinical findings and provide one possible explanation for incongruities in the clinical fracture risk and femur strength literature.
股骨几何形状和身体成分的指标与临床髋部骨折风险相关。这些关系的机制解释通常集中在股骨强度上；然而，冲击负荷也调节骨折风险。我们评估了股骨几何形状和身体成分对股骨颈侧向冲击时的应力的潜在影响。15 名女性志愿者在臀部上完成低能量的侧向摔倒。此外，参与者分别完成了超声和双能 X 射线吸收测定成像，以分别描述髋关节上的转子间软组织厚度（TSTT）和股骨的六个几何形状指标。分别建立并利用了基于个体的梁模型，利用实验冲击动力学来计算股骨颈峰值应力（σ）。除了股骨颈轴长度之外，股骨几何形状的所有指标均与σ呈正相关（均 p<0.05）。较大/更突出的股骨近端与股骨近端的力增加有关，而较宽的颈干角与独立于力的更大的应力产生有关（均 p<0.05）。体质指数（BMI）和 TSTT 与σ呈负相关（均 p<0.05）。尽管存在很强的相关性，但这些身体成分指标似乎通过不同的机制影响股骨颈的应力。增加的 TSTT 与股骨近端的力减少有关，而增加的 BMI 与抵抗应力产生的能力增加有关（均 p<0.05）。本研究提供了对股骨几何形状和身体成分可能调节髋部骨折风险的机制途径的新见解。我们的发现补充了临床发现，并为临床骨折风险和股骨强度文献中的不一致提供了一种可能的解释。
