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Erschienen in:
01.11.2009 | Original Article
High incidence of loosening at 5-year follow-up of a cemented metal-on-metal acetabular component in THR
Erschienen in: European Journal of Orthopaedic Surgery & Traumatology | Ausgabe 8/2009
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Introduction
High rates of polyethylene wear in metal-on-polyethylene-bearing surfaces correlate with peri-prosthetic osteolysis and early loosening. Hard-bearing surfaces have been used as they may decrease the production of debris and improve survival of the prosthesis. The aim of this study is to ascertain the rate of early loosening of a polyethylene cemented acetabular component with a metal-on-metal (MOM) insert.
Methods
Between 1997 and 1999, 121 total hip replacements in 114 patients were performed at a single centre by two senior surgeons, using the same prosthesis with a MOM hard-bearing surface of 28 mm diameter. At the mean follow-up of 5 years and 6 months (range 5–7 years), nine patients had died and three were lost to follow-up. We reviewed 107 hips (101 patients). The radiographs and case notes of deceased patients were examined. Follow-up was thus 117 out of 121 hips (96%). Results were evaluated clinically with the Merle d’Aubigne classification, and radiographically with analysis of implant migration and radiolucent lines in the Delee and Charnley areas. The survival rate was calculated.
Results
Six patients (5.6%) had revision surgery for aseptic loosening of the cup: one 2 years after the primary operation, two after 4 years, two after 5 years and one after 6 years. The clinical results according to Postel-Merle d’Aubigne gave 85 excellent results (80%), 10 good results (9.4%) and 6 bad results (5.6%). At the latest follow-up, there were no signs of migration, osteolysis or radiolucent lines involving the femoral component. In the acetabular component, there were five cases of radiolucent lines smaller than 1 mm, which were not progressive. In 24 cases, the radiolucent lines progressed over time and there was a probable failure in 18 cases. The survival rate at 5 years is 94.8% taking revision for any cause as the endpoint and 86.9% taking revision or impending failure (as ascertained by radiographic review) of the cup as the endpoint. Numbers of revisions and radiographic failures were significantly higher with the smaller cups (<48 mm diameter) than the larger (p < 0.05).
Conclusions
This series reports a higher rate of failure with a cemented polyethylene cup with a MOM insert than that reported in the scientific literature for metal-on-polyethylene-bearing surface or MOM uncemented cups. Other similar studies found in the literature are discussed. The authors do not recommend use of this cemented polyethylene-Metasul® acetabular component.