Mourtada F A, Beck T J, Hauser D L, Ruff C B, Bao G
Departments of Radiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21287-0849, USA.
J Orthop Res. 1996 May;14(3):483-92. doi: 10.1002/jor.1100140319.
The investigation of individual differences in hip strength requires a method to measure structural geometry in vivo and a valid analytical approach to calculate mechanical stress. We developed a method for deriving structural geometry of the femur from the proximal shaft through the femoral neck, using data from dual energy X-ray absorptiometry. The geometric properties are employed in a two-dimensional curved beam model of the proximal femur to estimate stresses on the lateral and medial bone surfaces. Stresses calculated by this method are compared with those from the conventional flexure formula and with results produced from a cadaver femur with use of three-dimensional finite element analysis of computed tomography data. Loading conditions simulating a one-legged stance and a fall on the greater trochanter are employed. Stresses calculated by curved beam theory are in much better agreement with three-dimensional finite element analysis than are those for which the conventional straight beam formula was used. In simulation of a fall on the greater trochanter, all three methods show peaks of stress at the femoral neck but only the curved beam and finite element analysis methods show an additional peak at the medial intertrochanteric margin. Both neck and trochanter regions correspond to common failure sites for hip fractures in the elderly. The curved beam treatment of hip structure derived from dual-energy X-ray absorptiometry provides an approach for the in vivo engineering analysis of hip structure that is not practical by other methods.
对髋部力量个体差异的研究需要一种在体内测量结构几何形状的方法以及一种有效的分析方法来计算机械应力。我们利用双能X线吸收法的数据，开发了一种从股骨干近端到股骨颈推导股骨结构几何形状的方法。将这些几何特性应用于股骨近端的二维曲梁模型，以估计股骨内外侧骨表面的应力。将该方法计算出的应力与传统弯曲公式计算出的应力以及使用计算机断层扫描数据进行三维有限元分析的尸体股骨结果进行比较。采用模拟单腿站立和大转子着地摔倒的加载条件。与使用传统直梁公式计算出的应力相比，曲梁理论计算出的应力与三维有限元分析的结果更为吻合。在模拟大转子着地摔倒时，所有三种方法都显示股骨颈处有应力峰值，但只有曲梁和有限元分析方法在内侧转子间边缘处显示出额外的峰值。颈部和转子区域都对应于老年人髋部骨折的常见骨折部位。从双能X线吸收法得出的髋部结构的曲梁处理方法为髋部结构的体内工程分析提供了一种其他方法无法实现的途径。
