Porous-coated anatomic total hip prostheses: radiographic analysis and clinical correlation

The radiographic changes of 46 bone-ingrowth, porous-coated anatomic total hip prostheses were reviewed and compared to the clinical outcome. The average postoperative follow-up was 32 months. The radiographic features that were assessed included subsidence; periprosthetic lucencies; periosteal, endosteal, and heterotopic new bone; loose beads; implant position; and tightness of fit. Clinical results were based on the Harris hip score. All acetabular components fared well. Three of the femoral stem components needed revision. The radiographic finding that correlated best with outcome was subsidence of more than 10 mm, especially if it continued to increase more than 1 year after surgery. Other findings related to failure were loosely placed femoral stems and the presence of loose beads. However, subsidence was such a powerful predictor of clinical outcome, and the other features were so weak, that combinations of variables did not improve the assessment of outcome. Close attention should be paid to subsidence in follow-up studies.