Comparison of wear and osteolysis in hip replacement using two different coatings of the femoral stem.

We compared the clinical and radiographic results of two matched series of total hip arthroplasties, one with hydroxyapatite-coated femoral stems, the other with a similar but porous-coated femoral stem. The prevalence of radiographic osteolysis was 16% in hips with hydroxyapatite-coated stems and 43% in hips with porous-coated femoral stems. In hips with hydroxyapatite-coated stems, osteolysis was always limited to Gruen zones 1 and 7. In contrast, distal osteolysis was present around 26% of the porous-coated stems. At 7 years, the survival-free rate of distal osteolysis was 100% in hips with hydroxyapatite-coated stems but 90% in hips with porous-coated stems (p=0.04). Circumferential hydroxyapatite coating of the femoral component reduced the occurrence of osteolysis and eliminated distal osteolysis at 5-10 years of follow-up. In addition, hydroxyapatite coating did not alter the wear rate.