Weight-bearing radiography in total hip replacement.

Serial anteroposterior (AP) radiographs of the weight-bearing pelvis and hips were taken of 29 patients with total hip replacement (THR). For constant positioning the patient stands with straight knees on a board with a block between the heels. A U-shaped mercury level strapped to the patient provides a horizontal reference line on the radiograph. On the average, individual variation of pelvic tilt in serial films was 1 degree and pelvic rotation 3.5 degrees confirming satisfactory reproducibility. The horizontal reference enables estimation of pre- and postoperative leg length inequality (LLI) and of the angle of the acetabular cup (AA). Reproducibility allows assessment of the exact position of the femoral component and quantitative evaluation of radiolucency and bone resorption around the prosthetic implant in the follow-up of THR.