HYDROXYAPATITE IN TOTAL HIP-ARTHROPLASTY - CLINICAL-RESULTS AND CRITICAL ISSUES

Surgeons who perform arthroplasties have posed some critical questions about hydroxyapatite, Does hydroxyapatite coating enhance bone ingrow th or ongrowth? Will hydroxyapatite lead to increased polyethylene wea r or an increased incidence of osteolysis? Will the hydroxyapatite coa ting disappear, and if so, what will be left to maintain implant fixat ion? A multicenter study of 316 hips (282 patients) with a proximally hydroxyapatite coated stem and either a hydroxyapatite or porous coate d cup were followed up 8.1 years (range, 5.6-9.9 years). The average p atient age was 50 years (range, 16-81 years), and 61% of the patients were male. One (0.3%) stem, three (2.7%) porous coated cups, and 25 (1 1.9%) hydroxyapatite coated cups were revised for aseptic loosening. D isappointing results on the acetabular side indicate that substrate de sign is critical. There were no cases of intramedullary femoral osteol ysis, and the incidence of acetabular and proximal femoral osteolysis and polyethylene wear was no greater than that seen with other cementl ess or cemented components. Based on these clinical results and a crit ical review of the literature, it is concluded that hydroxyapatite coa ted hip components do enhance ingrowth or ongrowth with no increased i ncidence of osteolysis for as many as 10 years. Concern about the disa ppearance of the hydroxyapatite coating with time seems moot in light of the above clinical findings.