Mid-Term Outcomes of Modular Dual Mobility Bearings in Total Hip Arthroplasty

Abstract

Modular dual mobility (MDM) prostheses in which a cobalt–chromium liner is inserted into a titanium acetabular shell have the potential for corrosion. This has raised concern. While these constructs have been shown to effectively reduce the risk of dislocation in revision and high-risk primary total hip arthroplasty (THA), previous studies have been limited by the length of follow-up. The purpose of the study is to review the mid-term clinical outcomes of MDM implants with a minimum of 5-year follow-up. A retrospective, observational study was conducted on all consecutive patients who underwent THA with a MDM implant from June 2011 and March 2017 at an urban, tertiary academic medical center. Descriptive statistics were used to describe baseline patient characteristics. Primary endpoints included revision rates, dislocations rates, and implant component survivorship. Implant survival was analyzed using the Kaplan–Meier method. A total of 92 cases (61 primary, 31 revision) underwent THA with a MDM implant at an average follow-up of 6.90 ± 1.48 years (range: 5.01–10.53 years). The mean patient age at the time of surgery was 58.20 ± 11.85 years. Six patients were revised (6.5%, 6/92), two for periprosthetic joint infection (2.2%, 2/92), one due to aseptic loosening (1.1%, 1/92), one due to periprosthetic fracture (1.1%, 1/92), and the remaining two for metallosis (2.2%, 2/92). Kaplan–Meier survivorship analysis showed a 93.5% survival rate for all-cause revisions and 98.9% survival for acetabular component revision. MDM components reliably decrease the risk of dislocation after THA. However, the occurrence of two revisions due to metallosis demonstrates the necessity for continued surveillance in this cohort. Larger trials with long-term follow-up may be required to further elucidate the long-term outcomes and performance of these bearings.