HYDROXYAPATITE COATING OF AN ACETABULAR PROSTHESIS

We report the radiological and clinical outcome of a press-fit (SLF) a cetabular component at two to three years in two groups of patients ha ving primary total hip replacement. In 69 the implant was coated with hydroxyapatite (HA) and in 40 it was uncoated. The stability of the cu p was assessed by measurement of proximal migration and change in the angle of inclination. The clinical results in the two groups did not d iffer significantly, and the mean proximal linear wear was similar in both, Fewer radiolucent lines (RLLs) were seen on the radiographs of c ups coated with HA. The mean proximal migration was studied by calcula ting regression lines for each patient using migration measurements: f or the SLF+HA group the mean slope was 0.06 mm/year and for the SLF-HA group 0.20 mm/year (p = 0.22). The change in the angle of inclination during follow-up was also consistently smaller in HA-coated cups. Usi ng regression methods the SLF+HA group had a mean slope of 0.08 degree s/year and the SLF-HA group 0.44 degrees/year (p = 0.023). Partial HA coating appeared to have no effect on the clinical outcome or on the r ate of wear of polyethylene, but there was a trend towards a reduced r ate of proximal migration, and a significant reduction in rotational m igration and the number of radiolucent lines. This suggests that HA co ating enhances the stability of this acetabular component.