Fifty-two pairs of patients who had had a total hip arthroplasty with a porous-coated femoral implant were studied in a retrospective, matched-pair analysis. Half of the patients had received a femoral component coated with hydroxyapatite and the other half (the controls), an identical component but without hydroxyapatite. The patients were matched for age, sex, weight, diagnosis, Charnley class, operative approach, and duration of follow-up. Identical uncoated hemispherical acetabular implants were used in both groups.
At the time of follow-up, at a mean of 2.2 years (range, two to 3.4 years) after the operation, the mean Charnley scores for pain, function, and motion were 5.6, 5.5, and 5.6 points, respectively, in the group that had received a hydroxyapatite-coated femoral component and 5.6, 5.6, and 5.6 points, respectively, in the group that had received a non-coated component; none of these differences were significant (p = 0.86, 0.89, and 0.80, respectively). There were no revisions in either group. Radiographs indicated stable fixation in both groups and no differences in the radiographic parameters of loosening between the two groups.
Within the relatively short time-frame of this study, there appeared to be no clinical or radiographic advantage to the use of hydroxyapatite in primary total hip arthroplasties. However, these results should be considered as preliminary. Longer follow-up may reveal unrecognized advantages or disadvantages.