Estimation of Femoral Head Size from Palpable Bony Prominences of the Femur

Proximal femoral surgeries involving femoral head replacement are common procedures worldwide. In these patients, the femoral heads are replaced with femoral head prosthetic implants. Pre-operative planning to determine the likely size of the prosthetic implant is important. Estimation from radiographs is the commonest method being used but this is fraught with problems. This study, therefore, developed an alternative method that can be used to estimate the femoral head size prior to hemiarthroplasty.

This was a prospective descriptive study that involved measurements of parts of femoral bone. Forty-eight adult femoral bones were measured. Measurements taken were the femoral head size (FH), the femoral bone maximum length (ML), the trochanteric length of the femur (TL), and the distal femoral breadth (DFB) of the femur. All measurements obtained were recorded and were analyzed using STATA version 13 (StataCorp, Texas, USA).

The maximum length of the femora ranged from 42.1 cm to 51.5 cm. The trochanteric length ranged from 39 cm to 48.3 cm. The distal femoral breadth ranged from 53.8 mm to 92.3 mm. The femoral head size ranged from 39 mm to 55 mm with a mean value of 46.6 ± 2.9 mm. An equation was generated using the trochanteric length. Femoral head size = 16 + 0.7(trochanteric length in centimeter) ± 5 mm. This will provide a range of possible femoral head prostheses that should be made available for the surgery.

This study generated an alternate method to be used during the pre-operative planning of a femoral head replacement surgery. It provides the possible range of prosthetic implants sizes to be made available for such surgeries. The trochanteric length can be easily measured. The method described will be of great benefit in middle and low income countries where prosthetic implants are not usually stocked within the hospital.