Dual Mobility Articulations in Primary Total Hip Arthroplasty: Midterm Outcomes from the American Joint Replacement Registry

Abstract

In recent years, there has been an increased utilization of dual mobility (DM) implants in primary total hip arthroplasty (THA) to mitigate the risk of postoperative hip instability. This study aimed to present midterm outcomes of DM bearings in primary THA using data from the American Joint Replacement Registry (AJRR). Screening was conducted on patients aged ≥ 65 years who underwent primary THA between 2012 and 2018. Patients were categorized into three groups: (1) DM articulation, (2) ≤ 32 mm femoral head, and (3) ≥ 36 mm femoral head. Multivariable statistical modeling was employed to analyze patient and hospital characteristics, minimizing potential confounding variables and identifying independent associations with revision. Cox proportional hazards regression analyses were used to assess all-cause revision and revision specifically for instability. A total of 207,526 primary total hip arthroplasties (THAs) were identified. Among them, 13,896 (6.7%) utilized dual mobility (DM) articulation, 60,358 (29.1%) had a femoral head size of ≤ 32 mm and 133,272 (64.2%) had a femoral head size of ≥ 36 mm. At the eight-year follow-up, the all-cause revision rate was higher in the DM group (3.5%, 95% confidence interval [CI] 3.1 to 4.1) compared to the ≤ 32 mm (2.6%, 95% CI 2.5 to 2.8) and ≥ 36 mm (2.7%, 95% CI 2.5 to 2.9) groups. However, the revision rate for instability was comparable among the DM (0.4%, 95% CI 0.2 to 0.5), ≤ 32 mm (0.5%, 95% CI 0.4 to 0.5), and ≥ 36 mm (0.3%, 95% CI 0.3 to 0.4) groups at eight-year follow-up. The utilization of DM was associated with higher overall revision rates. However, no significant differences in rates of revision for instability were observed among any of the bearing surface groups. These findings may be attributed to surgeons selectively utilizing DM articulations in higher-risk patients.