CATEGORY: MOBILITY, BONES & JOINTS
For an older adult, a broken hip usually means surgery within days, and for about half of these fractures the operation is a full hip replacement. The most common major complication afterward is the new joint popping out of its socket. A large trial has now shown that a different implant design makes that far less likely: 1.3% of patients who got a dual mobility implant dislocated within a year, versus 4.2% with a standard one, roughly a 70% reduction.1
A Ball Inside a Ball
A standard hip replacement swaps the damaged ball and socket for a metal or ceramic ball moving inside a fixed cup. The dual mobility design adds a middle layer. Its small metal ball snaps into a larger free-spinning plastic ball, which then glides inside the cup, the way a ball bearing rolls inside its race. That extra layer lets the hip move further before it can lever itself out. Surgeons already know how to implant both kinds, so nothing new has to be learned. The dual mobility version simply costs more, which is why proof has mattered.
Sixteen Hundred Patients, Two Countries, One Year
The Duality trial enrolled 1,600 adults aged 65 and older with a displaced femoral neck fracture, a break just below the ball of the hip, at 44 hospitals in the UK and Sweden. A computer draw, not the surgeon’s preference, decided which implant each patient received. Neither design was modified for the study. Researchers then tracked everyone for a year, counting dislocations, infections, repeat operations and deaths. These weren’t hand-picked healthy patients. Nearly one in twenty died within the year, which is the sober reality of hip fracture at this age.
Fewer Dislocations, and Fewer Complications Overall
Ten of 779 dual mobility patients dislocated, against 33 of 787 with the standard cup.1 The combined rate of any surgical complication was halved, 3.0% versus 6.1%. Infections and repeat operations on their own showed no meaningful difference, and deaths were essentially identical in both groups. The designers had planned around a 7% dislocation rate with standard cups and hoped the new design might cut that in half. Standard cups did better than feared, and the dual mobility advantage ran deeper than the team had assumed. Earlier small studies had hinted the design might trade fewer dislocations for more infections. That trade never showed up here.
What’s Still Unsettled
One year can’t reveal slow problems, such as the plastic layer wearing down over a decade. Quality-of-life scores came out the same in both groups, probably because most people in either group never had a complication at all. And the economics are still being worked out: the implant is pricier up front, while its complications cost less to treat. The researchers, funded by the Swedish and UK public research agencies, concluded the dual mobility design should be considered the preferred option for older patients having a hip replaced after this kind of fracture.
Key Takeaways
- Dislocation within a year happened to 1.3% of hip-fracture patients given a dual mobility implant versus 4.2% with a standard one, in a randomized trial of 1,600 older adults.
- Overall surgical complications were about half as common with the newer design, while infections, reoperations and deaths on their own didn’t differ.
- Follow-up lasted one year, so long-term wear of the extra plastic layer remains an open question, as does cost-effectiveness.
References
- Hailer NP, Griffin XL, Mukka S, et al. Dual mobility versus standard cups in total hip replacement for displaced femoral neck fractures (Duality): an international, multicentre, randomised, controlled, superiority trial. The Lancet. 2026;408(10552):348–356. link