Hydroxyapatite-coated uncemented implants and peri-implant infection

Abstract

One of the major complications of joint replacement surgery is a peri-implant infection. A hip prosthesis coated with hydroxyapatite, a calcium phosphate (found in human bone), may offer protection in this respect. In a series of patients who were treated with a hydroxyapatite-coated hip prosthesis for their osteoarthritis, excellent clinical performance and radiographic appearance were found after 5 and 10 years. Radiographically there were signs of osseointegration of the proximal part of the prosthesis; in the course of time the bone changes were also observed more distally. The failure rate for infection was low. The histologic features of the bone surrounding the prosthesis in patients with an uneventful postoperative course were similar to that of a patient who sustained a postoperative infection, which had been treated without removing the prosthesis. Experimental research consisted of comparison of two implants in an animal model. Half of the implants were contaminated with a known quantity of Staphylococcus Aureus. After 4 weeks, cultures showed more infections around hydroxyapatite-coated titanium implants as compared to noncoated titanium implants; the infections next to the hydroxyapatite-coated implants were also more severe histologically. Histomorphometric analysis revealed less osseointegration of parts of the hydroxyapatite-coated implants. The benefit of a hydroxyapatite coating in relation to peri-implant infection has therefore not yet been confirmed. Optimism remains however, in view of our clinical experiences, and also since the use of a hydroxyapatite-coated prosthesis in revision surgery for septic loosening of a hip prosthesis showed good clinical performance and the same radiographic features as in primary hip replacements.