Ford C M, Keaveny T M, Hayes W C
Department of Orthopaedic Surgery, Beth Israel Hospital and Harvard Medical School, Boston, Massachusetts, USA.
J Bone Miner Res. 1996 Mar;11(3):377-83. doi: 10.1002/jbmr.5650110311.
As with any structure, the structural capacity of the proximal femur depends on the applied loads and these can vary as a function of impact direction during a fall. However, despite its potential importance in hip fracture risk assessment, the relative importance of impact direction is unknown. To investigate the role of impact direction in hip fracture, we developed a detailed finite element model of the proximal femur. We analyzed four loading configurations that represent a range of possible falls on the greater trochanter. Our results indicate that a change in the angle between the line of action of the applied force and the axis of the femoral neck from 0 degrees (representing a direct lateral impact) to 45 degrees (representing a posterolateral impact) reduced structural capacity by 26%. This weakening of the femur with changes in impact direction is comparable to the weakening associated with 2-3 decades of age-related bone loss. Our result elucidates the independent contribution of fall mechanics to hip fracture risk by identifying an aspect of the fall (the direction of impact) that is an important determinant of fall severity. The results can also be incorporated into a refined clinical method for assessment of hip fracture risk that accounts for the complex interactions between fall severity and bone fragility.
与任何结构一样，股骨近端的结构承载能力取决于所施加的负荷，而这些负荷会因跌倒时的撞击方向而异。然而，尽管撞击方向在髋部骨折风险评估中可能具有重要意义，但其相对重要性尚不清楚。为了研究撞击方向在髋部骨折中的作用，我们建立了一个详细的股骨近端有限元模型。我们分析了四种加载配置，它们代表了大转子上一系列可能的跌倒情况。我们的结果表明，施加力的作用线与股骨颈轴线之间的角度从0度（代表直接侧向撞击）变为45度（代表后外侧撞击）时，结构承载能力降低了26%。随着撞击方向的变化，股骨的这种弱化程度与2至3十年与年龄相关的骨质流失所导致的弱化程度相当。我们的结果通过确定跌倒的一个方面（撞击方向），即跌倒严重程度的一个重要决定因素，阐明了跌倒力学对髋部骨折风险的独立贡献。这些结果还可以纳入一种改进的临床方法，用于评估髋部骨折风险，该方法考虑了跌倒严重程度与骨质脆弱性之间的复杂相互作用。
