Dual-mobility hips traded dislocations for periprosthetic fractures

Design

Single-centre retrospective propensity-matched cohort

Population

780 matched uncemented total hip replacements (260 dual mobility, 520 ceramic-on-ceramic)

Primary outcome

Periprosthetic femoral fracture and dislocation

Effect

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

This single-centre retrospective study compared 425 uncemented total hip replacements with dual-mobility bearings and 990 with ceramic-on-ceramic bearings done between 2017 and 2024. Propensity matching for age, sex, BMI and indication produced 260 dual-mobility and 520 ceramic-on-ceramic hips.

Periprosthetic femoral fracture occurred in 4.0% with dual mobility and 0.8% with ceramic-on-ceramic overall (OR 4.8), and the difference held after matching (OR 3.5, 95% CI 1.3 to 8.6). Dislocation went the other way: 0.4% against 4.0% after matching (OR 0.09). Surgery for femoral neck fracture independently raised the risk of both fracture and dislocation, and the trade-off was similar whatever the indication.

The authors suggest that energy which would otherwise dislocate the hip is transmitted down the stem into bone. For surgeons using dual mobility routinely for neck-of-femur fractures in frail, osteoporotic patients, this is a reason to think about the stem and its fixation, not to abandon dual mobility, whose dislocation benefit here was large.

• Weigh dislocation risk against periprosthetic fracture risk when choosing dual mobility.
• Consider stem design and fixation carefully in osteoporotic bone, particularly with dual mobility and uncemented stems.
• Counsel patients having arthroplasty for neck-of-femur fracture that both dislocation and periprosthetic fracture are more likely.
• Address falls risk and bone health after surgery, whatever bearing is used.

Why it matters

Dual mobility is often chosen for its dislocation benefit alone; this puts a cost on the other side of the ledger.

Don't overread it

This is a retrospective single-centre series; uncemented stems were used throughout, and unmeasured differences between groups may remain.

The statistics, in plain English

An odds ratio of 3.5 after matching means the odds of periprosthetic 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 size is uncertain. The dislocation odds ratio of 0.09 means about a tenth of the odds, also from small numbers.

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