Uncoated polyethylene RM acetabular component versus Müller cemented acetabular component. A 4- to 8-year follow-up study.

Comparable patient populations with 160 uncoated RM acetabular cups and 263 cemented Müller standard acetabular cups were submitted to survival-time analysis in a retrospective study with a mean follow-up of 5.3 years for the RM cup and 6.1 years for the Müller cup. After 7-8 years 12% of the RM cups and 4% of the Müller cups had been exchanged, 40% and 15% respectively were loose. The poor performance of the RM cups is ascribed to additional external polyethylene wear, which leads to the formation of granulomas and destroys the weight-bearing osseous structures. Similar granulomas also develop on the proximal stem and thus endanger the same.