The Metasul Metal-on-Metal Total Hip Arthroplasty: A Minimum 15 Year Follow Up

Introduction: Polyethylene-induced osteolysis in total hip arthroplasty (THA) in the 1980’s led to the re-introduction of metal-on-metal (MM) THA in an attempt to reduce wear particle debris.. The Metasul (Sulzer) was introduced as a promising interface with improved manufacturing technology, better clearances and enhanced metal hardness. This study reports our long-term results (minimum 15 years) of patients that received the Metasul bearing.

Methods: Between July 1997 and August 2001, 105 consecutive primary Metasul MM THAs were performed in 94 patients (57 males and 37 females). All patients received a cementless titanium femoral and acetabular component and a 28mm cobalt/chrome femoral head. The mean age of patients at time of surgery was 50 (range: 17-65) years. Cobalt (Co) and chromium (Cr) levels were measured. Cup inclination and anteversion was measured by Einzel-Bild-Roentgen-Analyse (EBRA) software on the radiographs at the last follow up visit.

Results: At a minimum follow-up of 15 (range 15-18) years, the mean HHS and UCLA scores for the surviving THAs were 88.9 and 6.3, respectively. Fourteen THAs were revised at a mean period of 2.5 years (range: 0.1-12.5 years). Eleven of the revised hips were due to failure of osseointegration of a recalled acetabular component. Additionally 1 patient required revision for an undersized stem, one patient required debridement and liner exchange for early infection and one patient was revised for pseudotumor. When excluding patients involved in the recall the survivorship of the bearing at a minimum of 15 years is 97.5%. Median Co and Cr level in whole blood were 1.24 and 0.83 μg/L, respectively. The acetabular component had an average inclination of 42.23° ± 6.1 (from 26° to 63°) and average anterversion of 16.99° ± 6.2 (from 3.3° to 20.3°).

Conclusion: Excluding the recalled components, Metasul articular interface has performed extremely well at a minimum follow-up of 15 years.