Morphology of the proximal femur differs widely with age and sex: Relevance to design and selection of femoral prostheses

The ability of uncemented femoral stems to osseointegrate properly depends largely on their fit in the proximal femur. We evaluated the topography of the proximal femur and determined differences based on age and sex. Retrospectively, anteroposterior radiographs from 312 (168 male, 144 female) pre‐operative total hip arthroplasty (THA) patients (age of 21–85 years) were collected. Radiographic measurements were taken at 10 mm intervals along the length of the femur. Variables including canal flare index (CFI) and cortical index (CI) were calculated. Data were binned into three age groups and separated by sex for comparison. Measurements showed that CFI decreased with age for both sexes; however, females demonstrated a greater decrease. Decrease in flare occurred primarily on the lateral side. CI also decreased with age, the most pronounced drop occurring in older females. A clear difference exists between male and female proximal femoral geometry. This decrease is most likely attributed to the loss of cortical bone. The medial component likely demonstrates less loss of flare due to strong compressive forces that are transmitted through this portion of the femur. These results demonstrate the necessity of considering age and sex when selecting a proper prosthesis.