FAILURE OF INTRAOPERATIVELY CUSTOMIZED NONPOROUS FEMORAL COMPONENTS INSERTED WITHOUT CEMENT IN TOTAL HIP-ARTHROPLASTY

Seventy-four primary total hip arthroplasties were performed in sixty- eight patients between August 1990 and September 1991. Clinical assess ments were made with use of the Harris hip score and, specifically, th e pain component of that score. The preoperative radiographs were digi tally quantified for calculation of the so-called canal-to-calcar rati o and the so-called cortical index. The postoperative radiographs were evaluated for the percentage of the cross-sectional area of the femor al canal that was occupied by the prosthesis; subsidence of the prosth esis; and adaptive osseous changes, including hypertrophic cortical re modeling, osteolysis, formation of sclerotic radiolucent lines around the prosthesis, and formation of a pedestal at the tip of the prosthes is. re indication for the arthroplasty was osteoarthrosis in fifty hip s (68 per cent), avascular necrosis in fourteen (19 per cent), congeni tal dysplasia in six (8 per cent), and another diagnosis in four (5 pe r cent). The average duration of follow-up was thirty-one months (rang e, eleven to forty-six months). The average Harris hip score (and stan dard deviation) was 75 +/- 16.8 points (range, 29 to 100 points), and the average score for the pain component was 37 +/- 7.5 points (range, 0 to 44 points). The average canal-to-calcar ratio of the hips,vas 0. 44 (range, 0.32 to 0.74), and the average cortical index was 0.54 (ran ge, 0.33 to 0.66). The average subsidence of the component was 0.6 cen timeter (range, 0.0 to 2.3 centimeters). The average fill of the canal was 100 per cent proximally, 97 per cent at the middle of the stem, a nd 92 per cent distally as measured on the anteroposterior radiographs made immediately postoperatively and 100, 95, and 90 per cent, respec tively, as measured on the lateral radiographs. A failure occurred in twenty-one hips (28 per cent) in twenty-one patients, with an average time to failure of 21 +/- 13 months (range, one to forty-four months). The Kaplan-Meier survival estimate (and standard error) for this popu lation was 0.45 +/- O.11 (confidence interval, 0.67 to 0.23) at forty- four months. The average subsidence of the components that failed was 0.7 centimeter (range, 0.1 to 2.3 centimeters). There was no significa nt relationship between failure of the component and the age or sex of the patient, the diagnosis, or the side of the operation. Postoperati ve severity of pain (p = 0.09) or subsidence (p = 0.08) alone did not reach significance for predicting outcome. The Harris hip score alone (p = 0.05), the Harris hip score in combination with subsidence of the femoral component (p = 0.01), and the pain component of the Harris hi p score in combination with subsidence of the femoral component (p = 0 .01) were all significant for predicting outcome. No other measured ra diographic variable was predictive of failure. Despite optimization of the fit of the component within the femoral canal and the percentage of the cross-sectional area of the femoral canal occupied by the compo nent, the clinical results indicated a high rate of failure. Thus, the se criteria are not the only requisites for stabilization of these fem oral components without cement. On the basis of these data, we have di scontinued the use of this intraoperatively customized, non-porous, sm ooth femoral prosthesis.