Function-orientated structural analysis of the proximal human femur.

In his model of the biomechanics of the proximal human femur, Friedrich Pauwels assumes a resultant force acting on the femoral head that is created by the partial body weight and the force of the abductor muscles inserting at the greater trochanter. This model suggests a tensile force in the region of the greater trochanter. An exact examination of the muscle insertions at the greater trochanter resulted in a contrasting hypothesis assuming a local compression stress in the region of the greater trochanter. The aim of this study was to examine which hypothesis is favored by the internal architecture of the proximal femur. Based on the architectural software Allplan(R), we performed an extended analysis of the trabecular structure within the proximal femur using CT scans of 10 human cadaver femora altogether. According to our results, both the medial and the trochanteric trabecular systems are orientated approximately perpendicular to the arcuate trabecular system [angles between systems ranging from 84.6 to 93.0 degrees (mean angle 90.7 degrees ) and from 80.9 to 86.5 degrees , (mean angle 84.9 degrees ), respectively]; furthermore, the medial trabecular system is orientated perpendicular to the epiphysis of the femoral head (mean of angles: 94.7 degrees ). The biomechanical interpretation of these results strongly supports the idea of compressive stress in the region of the greater trochanter and makes a predominant tensile force of the abductor muscles highly unlikely.