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Tomasz Poboży

Dual mobility in THA for femoral neck fracture: fewer dislocations in DUALITY

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Tomasz Poboży

Polish version: Podwójna mobilność w THA po złamaniu szyjki kości udowej — mniej zwichnięć

Dual-mobility cups can substantially reduce dislocation after total hip arthroplasty (THA) for displaced femoral neck fracture. In the pragmatic DUALITY trial published in The Lancet, dislocation requiring reduction or surgery within 1 year occurred in 1.3% with dual mobility and 4.2% with standard cups.

Why this study matters

Dislocation is a major early complication of THA for femoral neck fracture in older adults, potentially requiring readmission, anaesthesia for reduction or further surgery. Dual mobility aims to improve stability. Earlier support largely came from observational evidence and small studies; DUALITY was the first large randomized trial designed to address the question in routine practice.

Study design

Patients aged at least 65 with displaced femoral neck fracture, already selected for THA, were recruited at 44 hospitals: 20 in Sweden and 24 in the UK. A total of 1,600 patients were randomized 1:1 to dual-mobility or standard cups. Patients and clinical teams knew the implant allocation, while investigators and statisticians remained masked until analysis was complete.

The primary endpoint was operated-hip dislocation within 1 year requiring closed reduction or surgery. The modified intention-to-treat analysis included 1,566 patients.

Main results

  • Dislocation occurred in 10/779 patients (1.3%) with dual mobility and 33/787 (4.2%) with standard cups.
  • The adjusted hazard ratio was 0.27 (95% CI 0.13–0.56; P < 0.0001).
  • The absolute risk difference was 2.9 percentage points.
  • The authors also found a lower overall risk of surgical complications with dual mobility.

The reduction concerned a complication with substantial functional consequences for older adults after fracture, making it clinically as well as statistically relevant.

Clinical interpretation for an orthopaedic surgeon

The strongest conclusion applies to patients aged ≥65 with displaced femoral neck fracture for whom THA has already been chosen. Dual mobility reduced first-year dislocation in that setting. Apart from cup allocation, treatment followed local practice across 44 hospitals. This increases variation in techniques and implants but also makes the trial more representative of routine care than a single specialist-centre study.

Limitations

  • Findings should not automatically be extrapolated to elective THA for osteoarthritis.
  • The study compared cups after selection for THA; it does not determine when THA is preferable to hemiarthroplasty.
  • Patients and treating teams were unblinded.
  • First-year outcomes do not resolve long-term wear, implant durability or rare late complications specific to dual mobility.
  • The overall result does not identify one brand or cup design as best.

Implications for practice

DUALITY provides strong support for considering dual mobility to reduce dislocation in older patients undergoing THA after displaced femoral neck fracture. It does not justify universal use in every primary THA, eliminate dislocation risk or establish superior long-term implant survival. Bone quality, patient function, approach, anatomy and team experience remain relevant to individual decisions.

References

  1. Poboży T, Janowski K, Michalak K, Rulewska N, Grabowski F, Konarski W. Total Hip Arthroplasty After Femoral Neck Fracture in an Ipsilateral High Transfemoral Amputee With Less Than 50% Femoral Length. Cureus. 2025;17(10):e95722. DOI: 10.7759/cureus.95722. This report concerns THA after femoral neck fracture in a particularly challenging technical setting; it does not compare cup designs.
  2. Hailer NP, Griffin XL, Mukka S, et al.; DUALITY Investigators. Dual mobility versus standard cups in total hip replacement for displaced femoral neck fractures (Duality): an international, multicentre, randomised, controlled, superiority trial. Lancet. 2026;408(10552):348–356. DOI: 10.1016/S0140-6736(26)00759-2. PMID 42392114.

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Content prepared by: Tomasz Poboży - orthopaedic surgeon.

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