Clinical and radiographic experience with a hydroxyapatite-coated titanium plasma-sprayed porous implant

The use of bioactive materials recently has given increased hope to achieving adequate fixation in cementless total hip arthroplasty. Hydroxyapatite, one of the most biocompatible materials known, interacts with surrounding bone and forms a chemical bond with the bone, rather than a mechanical microinterlock via bioingrowth. There is direct bonding of bone and the hydroxyapatite, as opposed to the development of an intervening fibrous tissue layer between the implant and the bone. Recent use of hydroxyapatite-coated implants has shown that very strong bonds with living bone occur within a relatively short period of time. In this article, 53 primary, cementless total hip arthroplasties, all performed by or under the direction of a codesigner of the prosthetic system, are reviewed. The average age of the patients at arthroplasty was 51 years; the follow-up period averaged 17 months. The preliminary results achieved in this group of patients were compared with those achieved in 50 patients who received the identical porous coated implant without hydroxyapatite. The preoperative diagnoses, Harris Hip Scores, and patient demographics were similar for both groups. A comparison of clinical results showed that patients with the hydroxyapatite-coated femoral implants experienced more rapid clinical improvement in the first 6 to 10 weeks after arthroplasty than the patients with the identical prosthesis without hydroxyapatite coating. Radiographically, in the hydroxyapatite group, there have been no femoral or acetabular component failures, and no instances of femoral component subsidence or acetabular component migration.