The Biomet Bi-Metric Total Hip Arthroplasty and Universal Acetabular Cup : High Polyethylene Failure Rate in the Medium Term

We report on the medium-term results of the Bi-Metric (Biomet UK Ltd, Bridgend, UK) uncemented total hip arthroplasty system used with the Universal acetabular cup and polyethylene liner secured with the Ringloc (Biomet UK Ltd) mechanism. Fifty-eight total hip arthroplasties in 49 patients (mean age at implantation, 57.1 years) were identified, with 45 hips followed up at a mean of 7.6 years (range, 5-13 years). Of those hips not requiring revision, the mean Harris hip score was 89, 87% of the hips were judged to be very good or good according to d'Aubigne and Postel (J Bone and Joint Surgery 1954;36A:451), and the radiographic criteria by Engh et al (Clin Orthop Relat Res 1990;257:107) demonstrated the femoral components to be well fixed. Six patients required a revision procedure at a mean of 6.2 years postsurgery, with all failures attributed to marked wear of the polyethylene liner.