Authors: Wyles CC, Van Demark III RE, Sierra RJ, Trousdale RT.
Mayo Clinic Rochester, MN
Title: High Rates of Infection Before and After Revision of Failed Metal-on-Metal Total Hip Arthroplasty: A Study of 50 Patients
Background: A growing body of evidence suggests that metal-on-metal (MoM) total hip arthroplasties (THA) have higher rates of failure and subsequent revisions than other bearing surfaces. Adverse reactions to metal debris (ARMD) have been shown to be a primary source of failure; however, these cases alone do not account entirely for the increased rate. There is little data demonstrating why these patients fail and how they fare after their revision surgery.
Hypothesis/Purpose: This study aims to review reasons of failure after primary MoM THA with particular attention to post-revision survivorship and reasons for subsequent revision.
Methods: We identified 50 sequential patients (50 hips) that had a MoM THA revised at one institution.
Results: The primary reasons for revision included: pain with loose components (38%); infection (26%); adverse reaction to metal debris (16%); periprosthetic fracture (8%); impingement (6%); dislocation (4%); and pain of unknown origin (2%). Patients were followed up for a mean of 33 months (range 24 - 81 months) postrevision. Survivorship free from further revision for any cause at 24 months was 94.0% and at final follow-up was 90.0%. Reoperation was required in 5 hips (10.0%), and the reason for all subsequent revisions was due to infection. These 5 patients had initially been revised for ARMD (N=2), infection (N=2), and dislocation (N=1). Harris Hip Scores improved from 44.5 pre-revision to 74.5 at final follow-up (p <.0001).
Discussion: In this series, infection is a significantly compromising factor in the survivorship of primary MoM THA as well as in the survivorship of revision implants. These rates of infection are above published results of their metal-on-polyethylene counterparts and highlight the possibility of ARMD increasing the likelihood of failure secondary to infection.
Conclusion: Metal-on-metal THA demonstrate high rates of failure primarily due to component loosening, infection, and ARMD. Additionally, post-revision complications due to infection are high in this series at 10%.