New method to estimate femoral head size from the trochanteric length of the femur.

Abstract

Preoperative planning is an important step before any joint replacement surgery. In developing countries standardised radiographs and planning tools might not be available but nevertheless hemiarthroplasties are performed in certain trauma cases. An equation should be devised to allow a preoperative estimation of the expected femoral head size dimensions in those situations. 35 lower limbs of human cadavers were studied. The estimated femoral head (EFH) size of each femur was obtained by measuring the trochanteric length (TL) (in cm) and using the equation 'EFH = 16 + (0.7 × TL)'. The hip joint was dissected, and the actual size of the femoral head (AFH) was measured on the specimen. There was a correlation between the EFH and AFH (<i>p</i> = 0.0001). Accepting a range of ±3 mm the femoral head size was predicted correctly in 31 hips (89%), for ±4 mm in 33 hips (94%) and for ±5 mm in 35 hips (100%), respectively. A simple tape measurement and the equation Femoral head size = {16 + (0.7 × Trochanteric Length)} ±5 mm gives a rather reliable guess for the expected femoral head size. It might be useful as pre-operative planning tool if no standardised radiographs are available.