Monoblock and Modular Dual-Mobility Constructs Versus Standard Cups with Femoral Heads ≥ 36 mm in Cementless Total Hip Arthroplasty for Femoral Neck Fracture: A 10-Year Comparative Registry Study of 10-Year Survival Estimates

Background and Objectives: Dual-mobility cups are commonly used to reduce instability after total hip arthroplasty (THA) for femoral neck fracture (FNF), but their advantage over contemporary large-head standard cups remains uncertain. This registry study compared revision-related survival estimates up to 10 years among monoblock dual-mobility cups, modular dual-mobility constructs, and standard cups with femoral heads ≥ 36 mm in cementless THA for FNF. Materials and Methods: We retrospectively analyzed regional residents undergoing cementless, non-metal-on-metal primary THA for FNF. The cohort included 4827 THAs: 1220 monoblock dual-mobility cups, 408 modular dual-mobility constructs, and 3199 standard cups with ≥36 mm heads. Groups differed in age and sex distribution, with modular dual mobility used in older patients and both dual-mobility constructs used more often in women. Kaplan–Meier analysis estimated survival up to 10 years using aseptic failure and revision for dislocation/instability as endpoints. Cox models estimated adjusted hazard ratios, and cumulative incidence of aseptic failure was assessed with death as a competing event. Results: Kaplan–Meier-estimated 10-year aseptic failure-free survival was 94.4% for monoblock dual mobility, 96.8% for modular dual mobility, and 95.4% for standard cups (p = 0.815). Cup construct was not independently associated with aseptic failure: compared with standard cups, the HR was 1.12 for monoblock dual mobility (95% CI, 0.75–1.67) and 1.34 for modular dual mobility (95% CI, 0.71–2.52). Kaplan–Meier-estimated 10-year survival free from revision for dislocation/instability was 99.6%, 99.2%, and 99.3%, respectively (p = 0.620), with no independent effect of cup construct. Male sex increased the risk of both aseptic failure and revision for dislocation/instability. Periprosthetic fracture was the leading cause of aseptic revision in both dual-mobility groups, whereas failures were more evenly distributed in the standard cup group. Death-adjusted cumulative incidence of aseptic failure was similar across constructs (p = 0.919). Conclusions: Neither monoblock nor modular dual mobility improved revision-related outcomes compared with standard cups using femoral heads ≥ 36 mm. Late survival estimates, particularly for modular dual mobility, should be interpreted cautiously because of the limited number of patients remaining at risk.