Dual mobility cut dislocation but was linked to more femoral fractures

Design

Single-centre retrospective cohort with propensity score matching

Population

1,415 uncemented THAs; matched 260 dual-mobility vs 520 ceramic-on-ceramic

Primary outcome

Periprosthetic femoral fracture and dislocation

Effect

Fracture OR 3.5 (95% CI 1.3–8.6); dislocation 0.4% vs 4.0%, OR 0.09 (0.02–0.49)

This single-centre retrospective study compared 425 uncemented total hip replacements with dual-mobility bearings against 990 with ceramic-on-ceramic bearings (2017–2024), then matched 260 against 520 for age, sex, BMI and indication.

Periprosthetic femoral fractures were more frequent with dual mobility: 4.0% vs 0.8% overall (OR 4.8), and still raised after matching (OR 3.5, 95% CI 1.3 to 8.6). Dislocations went the other way — 0.4% vs 4.0% after matching (OR 0.09, 0.02 to 0.49). Surgery for femoral neck fracture independently raised the risk of both. The authors suggest that energy which would otherwise dislocate the hip is passed down the stem into the femur.

Dual mobility is often chosen precisely for frail patients after hip fracture, who are also the patients at highest fracture risk. This does not argue against dual mobility, but it does argue for thinking about stem fixation in the same decision. Cemented stems, which are associated with fewer periprosthetic fractures in older bone, were not studied here.

• When choosing dual mobility for instability risk, weigh the periprosthetic fracture risk too.
• In older patients with femoral neck fracture, consider a cemented stem when using dual mobility.
• Counsel patients that a bearing that resists dislocation may transfer a fall's energy to the femur.
• Prioritise falls prevention and bone health after any arthroplasty for hip fracture.
• Interpret this alongside registry data; it is one centre's uncemented experience.

Why it matters

A bearing chosen to solve dislocation may shift the failure to the femur in the same frail patients.

Don't overread it

Retrospective and single-centre with uncemented stems only — it does not show the bearing itself causes fractures.

The statistics, in plain English

An odds ratio of 3.5 after matching means much higher odds of fracture with dual mobility, but the wide interval (1.3 to 8.6) reflects small numbers of events. The dislocation odds ratio of 0.09 means dislocation was roughly ten times less likely. Matching cannot remove differences in who was chosen for each bearing that were not recorded.

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