Early Failure of Hemispheric Hydroxyapatite-coated Acetabular Cups

Abstract

Total hip arthroplasties with hydroxyapatite coatings have shown encouraging results after early-term followup. We presumed hydroxyapatite-coating on a smooth hemispheric press-fit acetabular cup would enhance bone osseointegration and maintain stability of cup after midterm (minimum 5-year) followup. Sixty-three patients had 70 consecutive total hip arthroplasties. Five patients (eight hips) died from problems unrelated to surgery. The remaining patients (62 hips) were followed up for an average of 7 years (range, 6-9 years). The mean age of the patients was 49 years (range, 23-61 years). The average Harris hip score improved from 59 points (range, 32-82 points to 82 points (range, 37-100 points) at final followup. There were seven acetabular component revisions. Of the 55 unrevised cups, 47 hips (85%) were stable by bony ingrowth, five hips (9%) were fibrous stable, and three hips (5%) were unstable with cup migration. Osteolysis around the cup was observed in 18 hips (33%). The average polyethylene wear rate was 0.15 mm/year. Survival rates of the cups at 6 and 8 years were 94.3% and 60.5%, respectively. Total hip arthroplasties using an hydroxyapatite-coated smooth hemispheric acetabular cup showed an unexpected high failure rate in terms of fixation, occurrence of osteolysis, and revision after midterm followup. Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.