Hydroxyapatite-coated total hip prostheses. Two-year clinical and roentgenographic results of 100 cases.

Studies of implant fixation have shown that hydroxyapatite (HA) coatings provide early and strong fixation to bone. This is a report of 100 consecutive cases of total hip arthroplasties, using HA coating, which were mainly for osteoarthrosis, avascular necrosis, or revision for failed implants. The average prospective follow-up period was two years. Titanium femoral components had a proximal HA coating, usually with an HA-coated screw cup. For both HA-coated components, the average Harris hip score was 96 points after one year and 98 after two years. Analysis of data shows that the incidence of pain was low immediately after surgery and at 4% one year postoperatively. There was no difference between the results of primary cases and revisions after the one-year interval. On roentgenographic examination, there was a rapid bony integration of implants with bone apposition on the coating within six months, accompanied by specific patterns of remodeling. No radiolucent line formation was detected around HA-coated implant parts. There were no revisions for loose implants. After two years, 97% of the patients had positive roentgenographic evidence of femoral ingrowth compared to 55% for HA-coated acetabular cups, with a statistical significance between bone ingrowth and clinical results. Implant fixation using HA coatings is a reliable procedure for good bony fixation and clinical results.