Measurement and restoration of equality in length of the lower limbs in total hip replacement.

Alteration of the length of the lower limb was measured in 39 patients undergoing total hip replacement. Radiographs were taken in the erect posture prior to operation and 6 months postoperatively. The inequality of limb length was measured by the difference between the height of the vertices of the femoral heads and by the difference between the lowest points of the ischial tuberosities. The change of the length was measured intraoperatively as the difference observed between two reference points: one above the acetabulum and the other on the proximal femur. Good correlation was obtained between the change of the limb length made intraoperatively and the change in the limb length using the ischial tuberosities as reference points; no correlation was observed when the vertices of the femoral heads were the reference points. Inequality of limb length can be radiologically determined before and after total hip arthroplasty. Femoral and prosthetic heads are not good reference points for measurement. The difference in the height of the ischial tuberosities demonstrates inequality of limb functional length as it reflects the tilting of the pelvis.