Lack of early dislocation for dual mobility vs. fixed bearing total hip arthroplasty: A multi-center analysis of comparable cohorts

Background: Dislocation is a major cause of morbidity and revision surgery following total hip arthroplasty (THA). To address such issues, dual mobility (DM) bearings were introduced as a more stable alternative to fixed-bearing (FB) prostheses. As such, we compared DM and FB systems in a cohort study in terms of dislocations, readmissions, and revisions. Methods: A 27 multi-center retrospective review was performed of 664 DM and 218 FB cases from the same manufacturer with mean follow-up of 2.09 years and 1.83 years, respectively. Patient reported outcome measures (PROMS) including Harris Hip Score (HHS), SF12, EQ5D, and Lower Extremity Activity Score (LEAS) were evaluated as well as dislocation rates, readmissions, and revisions rates. We also performed a survivorship analysis through Kaplan-Meier estimator. Students t-test was used for normally distributed continuous data and Fisher exact test (P < 0.05) was used for discrete data. Results: There were 0 dislocations in the DM (0%) group and 2 dislocations in the FB (0.92%) group (p = 0.06). Latest follow up HHS revealed a significant difference between groups (91.44 DM and 87.81 FB; p = 0.006). In addition, there was significant difference between DM and FB on SF12 Physical Component Score (PCS) (46.83 and 44.55, respectively, p = 0.015). Also, readmission rates at 30, 60 and 90 days remained lower for DM than for FB at each time point (1.05% vs. 2.75%, 1.81% vs. 2.75%, and 1.81% vs. 2.75, respectively). Overall, DM had a lower revision rate at 1.51% compared to 2.29% for FB (p = 0.24). The revision breakdown for DM revealed 0 (0%) for both Anatomic Dual Mobility (ADM) and Modular Dual Mobility (MDM) due to the acetabular component) There was a difference, 14 (87.5%) for ADM and 2 (12.5%) due to the femoral component. The survivorship analysis revealed no significance difference between DM and FB at 4 years (97.90% and 97.26%, respectively). Conclusion: In comparison to patients who undergo FB THA, DM bearings have improved PROMS and a lower rate of dislocation, readmission, and revision.