CONSTRAINED ACETABULAR COMPONENTS

Between May 1987 and October 1990, 21 constrained acetabular component s were used in revision total hip arthroplasty at the University of Ca lifornia, San Francisco. In 18 patients, the device was placed for a c hronically dislocating total hip arthroplasty. In the remaining three, intraoperative instability during revision total hip arthroplasty nec essitated its use. At the minimum I-year follow-up evaluation (average , 31 months; range, 24-64 months), 15 patients (71%) experienced no fu rther dislocations or subluxations. There were eight dislocations in t he remaining six patients (29%). The average Harris hip score at the f ollow-up evaluation was 76 points (range, 32-100 points). For those pa tients who redislocated (n = 6), an increased acetabular abduction ang le of the metallic acetabular cup, averaging 70 degrees, was the only predictive factor of failure of the constrained cup (P < .05). No radi ographic or clinical evidence of loosening in the 19 porous ingrowth a cetabular components was observed. This device will, relieve the compl ication of severe hip instability in the majority of patients, but is not universally successful.