Relationship between femoral head size and distance to lesser trochanter.

Hemiarthroplasty of the hip is a common treatment for displaced fractures of the femoral neck. However, accurate restoration of leg length may be difficult to achieve because intraoperative measurements of leg length and preoperative templating are limited by the fracture. Our primary question was whether femoral head diameter can be used to predict femoral head height. We analyzed 34 cadaveric femora to determine diameter of the femoral head, distance from the lesser trochanteric sulcus to the external center of the femoral head (head height), lateral distance from the proximal tip of the greater trochanter to the center of the femoral head (offset), and the femoral neck/shaft angle. The femoral head diameter had a linear correlation with head height expressed by the following equation: head height = 1.035 x femoral head diameter. Our results indicate the diameter of the femoral head is similar in size to the distance from the top of the lesser trochanter to the center of the femoral head in an average population of cadavers. This may be a helpful clinical measurement to assess leg length during surgical treatment of hip fractures.