Long-Term Screening is Necessary in Patients with Metal on Metal Total Hip Arthroplasty

Introduction: Adverse reactions to metal debris with catastrophic failures have been seen with a number of metal on metal (MoM) total hip designs. Understanding survivorship and factors associated with failure will allow for more targeted surveillance of those patients at highest risk for failure. The purpose of this study was to assess the mid to long term survivorship and specific factors associated with failure for a large cohort of a single modular MoM design.Methods: Consecutive patients treated with a modular metal on metal bearing with a five to fourteen year follow-up were included. Clinical outcome scores and radiographic data were prospectively collected.  Failure was defined as revision of either component for any reason during the study period. Multiple implant, surgical, and patient factors were analyzed for associations with elevated ion levels or revision due to adverse reactions to metal debris.Results: The average age at the time of surgery for the 253 patients included in the study was 55. There were 28 revisions (7.5%), eight due to metallosis (2%).   Survivorship was 89% at 12.6 years with revision for any reason as the end point. Survivorship was 93% when limited to revision for ALTR as the end point. Time in situ was the only variable that was statistically associated with an increased risk of failure due to ALTR (p<0.0001)Conclusion: In this large series of a single design modular metal-metal total hip we found relatively low rates of revision due to adverse reactions to metal debris.  The only variable associated with a statistically significant risk of ALTR was time in situ.   Therefore, long-term surveillance is necessary in patients with a MoM THA.