Dual Mobility Versus Jumbo Head (≥ 40 mm) Following Primary Total Hip Arthroplasty: A Registry-Based Cohort Study.

Abstract

Instability remains a leading complication following primary total hip arthroplasty (THA). Large articulations enhance stability by increasing jump distance and range of motion. Dual mobility (DM) and ≥ 40 mm jumbo heads (JH) are both large articulation options when compared to ≤ 36 mm heads, and debate exists between these two given differences in complexity, cost, and failure mechanism. We conducted a United States registry-based cohort study to compare DM and JH. Adults who underwent primary THA between 2010 and 2024 were included. There were 9,532 THA (1,716 DM and 7,816 JH) included. To mitigate confounding by indication and by implant generation, only cases that used DM or JH with acetabular implants compatible with both options were included. The primary outcome was dislocation; secondary outcomes were all-cause revision, aseptic revision, and revision for instability. Crude incidence was calculated at six years. Propensity score-weighted Cox proportional hazards regressions were used to evaluate revision risk. Dislocation incidence was 2.4 and 2.2% for DM and JH, respectively. We observed a time-based difference in dislocation risk: DM was associated with a lower risk before 4.25 years (hazard ratio (HR): 0.52, 95% confidence interval (CI): 0.32 to 0.85), but a higher risk after 4.25 years (HR: 8.26, 95% CI: 1.82 to 37.48). There were no differences found in all-cause (HR: 1.22, 95% CI: 0.72 to 2.07), aseptic (HR: 1.47, 95% CI: 0.73 to 2.93), or instability-related revision risk (HR: 1.71, 95% CI: 0.79 to 3.69). Use of a DM was associated with fewer early dislocations, but possibly more late dislocations, although late differences were small and later follow-up was limited. There was also no detectable difference in revisions, including for instability. While DM's marginal size advantage may avoid a small number of early closed dislocations, current large articulation options may be sufficiently similar to mitigate major revision differences. Most early JH dislocations were successfully treated closed, and conversely, the fewer early DM dislocations more often required revision.