Comparison of Outcomes Between Modular Dual Mobility and Conventional Hip Implants in Primary, Elective Total Hip Arthroplasty.

Introduction: Modular dual mobility designs (MDM) are designed to reduce the risk of postoperative dislocations following primary total hip arthroplasty (THA). This study investigated both the usage and outcomes (ie, patient-reported outcomes and complications) associated with MDM hips compared with conventional implant designs.

Methods: Patients who underwent a THA at a single, tertiary, orthopaedic specialty hospital between January 2019 and June 2022 were included. Primary outcomes of interest were compared between MDM and conventional hip designs and included complication rates, dislocation rates, clinical outcomes, and the hip disability and osteoarthritis outcome score for joint replacement (HOOS, JR).

Results: A total of 2869 patients (88% conventional THA) were included in this study. Modular dual mobility hip utilization increased 117% during the study period. Patients in the MDM group were often older females (P < 0.001) with concomitant lumbar pathology (P = 0.034). None of the MDM hips dislocated in the first 30 days post THA compared with 0.4% of the conventional hips. Despite markedly lower hip disability and osteoarthritis outcome score for joint replacement scores in the MDM group, the number of patients reaching the minimally clinically important difference was similar (P = 0.915).

Conclusion: MDM patients experience lower rates of dislocation compared with those receiving conventional implants. Despite worse clinical outcomes and increased all-cause emergency department utilization in the MDM group, multivariate regression suggests that these outcomes were associated with the implant being used in an older, sicker population instead of the implant itself. The results suggest similar overall outcomes and a lower dislocation rate for patients who received an MDM hip.