Clinical results two years after total hip arthroplasty with a dual-mobility hemispherical cup

Background: Dislocation remains a significant complication following primary total hip arthroplasty (THA). While dual-mobility (DM) acetabular components effectively mitigate instability through an increased jumping distance and head-to-neck ratio, traditional designs featuring protruding cylindrical-spherical rims are associated with a risk of iliopsoas impingement due to anterior acetabular overhang.

Objective: This study aimed to evaluate the clinical outcomes, dislocation rates, and revision frequencies of a specific hemispherical DM cup designed without a protruding rim after a minimum follow-up of two years.

Key Points: A retrospective analysis was conducted on 332 consecutive primary THAs performed via a posterolateral approach using a cementless hemispherical DM component. Clinical assessment utilized the modified Harris Hip Score (mHHS) and Oxford Hip Score (OHS). At a mean follow-up of 2.8 years, no dislocations were recorded. The cumulative revision rate for the acetabular component was 0.6%, with an overall revision rate of 1.5%. Postoperative complications included symptomatic iliopsoas impingement in 0.9% of cases (n=3), which is lower than reported rates for traditional DM and unipolar designs. Mean functional scores were high, with an mHHS of 92 ± 12 and an OHS of 57 ± 5. Multivariate analysis indicated that functional outcomes were inversely correlated with patient age, while mHHS showed a positive correlation with acetabular cup diameter.

Conclusion: The use of a hemispherical DM cup without a protruding rim provides effective stability against dislocation while maintaining favorable functional outcomes. The observed low incidence of iliopsoas impingement suggests this design modification may address soft tissue irritation concerns associated with conventional DM components, though long-term radiographic and clinical surveillance is required.