Dual mobility: fewer dislocations, more periprosthetic fractures

Design

Single-centre retrospective propensity-matched cohort

Population

780 matched uncemented THAs (260 dual-mobility, 520 ceramic-on-ceramic)

Primary outcome

Periprosthetic femoral fracture and dislocation

Effect

Fracture matched 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 dual-mobility total hip replacements with 990 ceramic-on-ceramic replacements performed between 2017 and 2024, then propensity-matched 260 dual-mobility to 520 ceramic hips on age, sex, BMI and indication.

Periprosthetic femoral fracture occurred in 4.0% of dual-mobility hips and 0.8% of ceramic hips (OR 4.8, 95% CI 1.86 to 12.4), and the excess held after matching (OR 3.5, 1.3 to 8.6). Dislocation went the other way: 0.4% vs 4.0% after matching (OR 0.09). Femoral neck fracture as the indication was independently associated with more of both complications.

The proposed mechanism is that energy which would dislocate a standard hip is transmitted down the stem instead. For hip fracture patients, often chosen for dual mobility precisely because of dislocation risk, this suggests the choice moves rather than removes risk. The findings come from one centre with uncemented stems; cemented fixation, which is preferred in many hip fracture pathways, may change the balance.

• Weigh periprosthetic fracture risk, not only dislocation, when choosing dual mobility.
• Consider cemented femoral fixation where dual mobility is used in osteoporotic or hip fracture patients.
• Counsel hip fracture patients that both dislocation and fracture risks are raised whatever the bearing.
• Audit local periprosthetic fracture rates by bearing type if dual mobility is used routinely.
• Note that the data come from uncemented stems at a single centre.

Why it matters

It challenges the assumption that dual mobility is a free gain in high-risk hips.

Don't overread it

This was a retrospective single-centre study of uncemented stems; it cannot prove the bearing causes fractures.

The statistics, in plain English

An odds ratio of 3.5 after matching means the odds of fracture were about three and a half times higher with dual mobility. The interval (1.3 to 8.6) is wide because there were few fractures, so the true excess could be modest or large. Matching balances measured factors but cannot balance unmeasured ones such as surgeon choice.

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