Cross-sectional geometry of the human femur in the mid-third region

Abstract

The design of a medical implant requires that the geometry and anatomy of the host region is fully understood. For any prosthesis to be located in the mid-third of the human femur it is therefore vitally important that an in-depth understanding of this region is obtained. This study focuses on the geometry of the medulla and the cortex and the relationship between them in the diaphyseal region of the human femur. Sixteen femora obtained from the Human Biology Department of the University of Leeds were sectioned at 10 mm intervals along the shaft and scaled photographs of each section were taken. These photographs then provided the raw data to enable the variation in long bone cross-sectional geometry to be evaluated. The results show that the medulla is almost cylindrical in the mid-third region, being most cylindrical between 35 and 50 per cent of the total bone length. The medullary width is found to be greater in the antero-posterior direction (>90 per cent maximum diameter) than in the medio-lateral direction (78-88 per cent maximum diameter) along the studied femoral length. The cortex is also analysed and it is found that the mean cortical thickness on the anterior side is significantly smaller than the medial cortex and the lateral cortex, with the posterior cortex being the thickest. All the above findings suggest that the medulla does not lie centrally within the femur but is positioned slightly anteriorly. Anatomical characteristics such as this can have profound effects on the design of prostheses to be implanted in this region.