Abstract
Introduction
The Metasul articulation was introduced in the early 1990's. It comprises a 28mm forged, cobalt-chrome head and a forged metal inlay, set into the polyethylene element of the acetabular component. During the 1990's and early 2000's anatomic sized MoM articulations were re-introduced for hip resurfacing and stemmed implant designs. Adverse tissue reactions to metal debris and corrosion products subsequently led to a decline in MoM usage.
Materials & Methods
Between January 1995 and December 1998, 133 hips underwent primary THR using the Metasul 28mm bearing. Patients were routinely sent an annual postal Oxford Hip Score (OHS) and radiographs were obtained from the second post-operative year. We have retrospectively reviewed the clinical and radiographic dataset following the 15 year follow-up time point.
Results
At a mean follow-up of 16.6 years (range 15.5–19.2 years), the median OHS score at 15 years was 42 (range 7–48). OHS showed statistically significant improvements at all post-operative time points when compared to pre-operative scores (p= <0.001; CI 4.42–6.69). No significant decline in OHS score was observed following the 15 year follow-up.
Nine hips were revised at a mean duration of 6.11 years (range 1.09–17.49). Worst case scenario Kaplan-Meier analysis, when lost patients were presumed revised, demonstrated an 84% (CI 0.77–0.90) survivorship at 15 years when revision for any cause was the endpoint. Aseptic loosening as the end point demonstrated an 88% survivorship (CI 0.81–0.93). One hip demonstrated femoral component migration of 2.7mm's but no component loosening's were observed.
Discussion
In contrast to the problems reported for other MoM articulations, our study suggests that the 28mm diameter Metasul bearing provides good survivorship and outcome at a minimum of 15 years. No long-term joint stability issues were identified. We have not assessed serum metal ion levels or quantified metal debris generation. Our patients remain under surveillance.
