Factors influencing the revision rate of Zweymueller acetabular cup.

Between January 1986 and December 1988, we implanted 220 conical-shaped Zweymueller threaded cups in 202 patients whose average age was 65 (33-83) years. The average thickness of the polyethylene (PE) insert was 8.0 (5.4-11.9) mm. In 142 cases, the corresponding femoral head was a 32 mm Al2O3 head. We followed 157 patients for a mean of 9.2 (1-16) years. Nine cups were revised and ten PE inserts replaced after an average of 11.9 (10-13.3) years. With cup revision alone considered as failure, the survival rate after 13 years was 89%. When both cup and insert revisions were considered failures, the survival rate decreased to 72% after 13 years. Patients younger than 60 years had a significantly higher rate of insert revision. Cup size 55 showed significantly more revisions in comparison to larger sizes. Using Cox regression model, neither gender, body mass index, nor material were risks factors leading to cup revision.