The porous coated anatomic total hip replacement. A ten to fourteen-year follow-up study of a cementless total hip arthroplasty.

BACKGROUND

We previously reported our two and five-year results of arthroplasty with the Porous Coated Anatomic total hip prosthesis. We now report on the performance of this prosthesis at ten to fourteen years.

METHODS

The results of 311 total hip replacements in which a Porous Coated Anatomic prosthesis was inserted without cement in 279 patients were analyzed prospectively. The average age of the patients at the time of the replacement was sixty--one years (range, twenty to eighty-one years). Sixty-four patients (seventy-six hips) died postoperatively. Forty-five patients (forty-seven hips) were lost to follow-up, and four were excluded because of their medical condition. One hundred and sixty-eight patients (187 hips) were followed for ten to fourteen years (average, twelve years). Seventeen of those patients (seventeen hips) had a revision.

RESULTS

The overall survival rate (with any revision as the end point) was 90.0% +/- 5.4% at fourteen years, with an average Harris hip score of 85 +/- 14 points. The prevalence of thigh pain was 36% (fifty-six of 157) in the late period (more than ten years postoperatively). Radiographs showed stable fixation, with bone ingrowth, of 83% (130) of the 156 acetabular components and 88% (137) of the 156 femoral components at the latest follow-up evaluation. Men had a significantly higher rate of femoral osteolysis than did women (p < 0.001). The rates of acetabular and femoral osteolysis associated with 32-mm femoral heads (49% [twenty-three] of forty-seven and 70% [thirty-three] of forty-seven, respectively) were significantly higher (p < 0.01) than those associated with 26-mm heads (26% [twenty-eight] of 109 and 30% [thirty-three] of 109, respectively). Despite this, revision (removal or exchange of components) was not directly related to head size; instead, it was related to polyethylene thickness.

CONCLUSIONS

There have been persistent problems with the Porous Coated Anatomic hip system, including thigh pain and an increasing prevalence of osteolysis with time. Revision because of aseptic loosening was related more to the thickness of the polyethylene liner than to the size of the femoral head. Femoral heads with a 32-mm diameter did not increase the risk for revision provided that an adequate thickness of polyethylene had been used.