HIP-REPLACEMENT WITH A THREADED ACETABULAR CUP - A FOLLOW-UP-STUDY

A study was begun in 1983 to determine the efficacy of a threaded acet abular cup. Fifty-five patients who had a total of sixty-eight threade d titanium cups had a complete clinical and radiographic evaluation ye arly. Fifty-two of the arthroplasties had been primary and sixteen, re visions. The average duration of follow-up was six years (range, five to nine years). Seventeen cups had to be revised at an average of sixt y-two months (range, twenty-seven to 108 months) after the index opera tion. Nine additional cups were loose and revision was pending at the most recent follow-up examination. Failure was defined as revision or pending revision. Thus, twenty-six (38 per cent) of the sixty-eight cu ps failed. Sixteen (31 per cent) of the fifty-two primary arthroplasti es failed and ten of the sixteen revision arthroplasties failed. Radio graphic changes that were evident in patients who had a failed cup con sisted of superomedial migration of the cup with osteolysis in Zone 3, as classified by DeLee and Charnley. These radiographic changes prece ded symptoms in most patients. Because of the high rate of failure of this acetabular component at six years, we believe that its use is not warranted.