REVISION TOTAL HIP-ARTHROPLASTY WITHOUT CEMENT - SUBSIDENCE OF PROXIMALLY POROUS-COATED FEMORAL COMPONENTS

We prospectively studied the intermediate-term results of forty-nine r evision total hip arthroplasties without cement that were performed be cause of aseptic loosening of a cemented femoral component in forty-fi ve consecutive patients; the mean duration of follow-up was sixty-five months (range, forty-five to eighty-seven months). A curved, long-ste m, titanium-alloy, non-circumferentially porous-coated femoral compone nt was implanted in each hip. Preoperatively, a staging system was use d to classify deficiencies of femoral bone stock according to the loss of cancellous or cortical bone in the metaphysis and diaphysis.Forty- one hips (84 per cent) had cortical or ectatic cavitary bone loss in t he metaphysis. The mean Harris hip score significantly improved from 5 4 points preoperatively to 84 points at the time of the latest follow- up examination (p < 0.001). Twenty-seven patients (twenty-eight hips; 57 per cent) had at least two millimeters of subsidence of the femoral component during the first postoperative year. Eight patients (eight hips; 16 per cent) had no further progression of subsidence. Twenty-on e patients (twenty-two hips; 45 per cent) had at least two millimeters of subsidence on two separate postoperative evaluations and therefore were considered to have progressive subsidence. Seventeen patients (n ineteen hips; 39 per cent) had no measurable subsidence and were consi dered to have a stable femoral component. One of these seventeen patie nts had had a bilateral femoral revision and had progressive subsidenc e on one side. There was a positive trend for an association between s ubsidence and the degree of preoperative femoral bone deficiency (p = 0.10), but there was no association between subsidence and the fit of the prosthesis in the metaphysis and diaphysis or the fill of the cana l of the femur (p > 0.50). There was no significant loss of bone in th e hips with either a stable or a subsided femoral component (p > 0.50) , and qualitative reconstitution of the cortex was noted in eleven (52 per cent) of the twenty-one most severely deficient (stage-III) femor a. Survivorship analysis showed that, at seventy-two months, there was a 96 per cent chance of survival of the component (95 per cent confid ence limits, 0.89 to 1.0) with revision as the end point but only a 37 per cent chance of survival (95 per cent confidence limits, 0.15 to 0 .59) with revision or progressive subsidence as the end point. The dat a indicate that revision,vith use of a curved, long-stem, non-circumfe rentially porous-coated femoral component without cement is associated with an unacceptable rate of subsidence.