| [ Summary ] |
It is difficult to estimate the bone strength of the femoral neck because the structure of the proximal femur is more complicated than that of the vertebral body of the lumbar spine. Many factors, such as the length of the femoral neck, neck-shaft angle, the cross sectional moment of inertia (CSMI), and the load on the femoral head, are needed to estimate the mechanical strength of the proximal femur. An algorithm was developed to estimate the strength of the femoral neck from data generated by dual-energy x-ray absorptiometry (DXA). Using this algorithm, CSMI and generated stress on the femoral necks of three aged people, a seventy year old woman with no fractures, a seventy-five year old woman with a subcapital fracture, and a seventy-four year old woman with an intertrochanteric fracture, were calculated. The changes of CSMI and stress along with the neck axis were different in the three cases, which were related to the presence of fractures or the type of fracture. In measurements of normal subjects, the superior half of the femoral neck loses bone mineral more rapidly than the inferior half. The center of mass of the cross section of the femoral neck moves to the inferior margin with age. This means that the stress generated on the superior margin increases with age. |