Dual-mobility THR reduces dislocation risk in THR recipients

In individuals who underwent a total hip replacement (THR) for a displaced femoral neck fracture, the risk of dislocation over the first year after surgery was lower among those who were treated with a dual-mobility THR (DM-THR) compared with those who received a standard THR, results from the Duality trial suggest.

In the modified intention-to-treat population, only 1.3 percent of participants in the DM-THR group had a dislocation within 1 year compared with 4.2 percent of standard THR recipients (adjusted hazard ratio [aHR], 0.27; p<0.0001). The per-protocol analysis showed a similar result (aHR, 0.16; p<0.0001). [Lancet 2026;408:348-356]

The DM-THR and THR groups had similar proportions of participants who underwent a re-operation of the index replacement for any indication (1.5 percent vs 1.9 percent; aHR, 0.77; p=0.49), who had a diagnosis of prosthetic joint infection (1.5 percent vs 1.9 percent; aHR 0.81; p=0.59), and who had died after a year (4.9 percent vs 4.8 percent; aHR, 1; p=1).

Compared with the THR group, the DM-THR group had a lower incidence of any surgical complication, including dislocation, prosthetic joint infection, or re-operation for any reason within 1 year (3 percent vs 6.1 percent; aHR, 0.45; p=0.001).

The cumulative incidence of the composite outcome of dislocation or death within 1 year was lower in the experimental vs control group (6.2 percent vs 8.8 percent; aHR, 0.66; p=0.026).

In the subgroup analysis, the incidence of dislocation within a year was lower with DM-THR vs THR among participants who underwent a posterior surgical approach (2.4 percent vs 7 percent) and a direct lateral surgical approach (0 percent vs 1.5 percent).

EQ-5D-5L* was similar between groups at 1 year (mean, 0.77 for both; p=0.79).

Two articulations

A standard THR, which involves a single joint between a small ball and the socket, is associated with a risk of dislocation when the ball disengages from the socket. This is the most common early surgical complication of THR. [Curr Rev Musculoskelet Med 2013;6:350-356]

“This complication often leads to revision surgery and impaired quality of life with the anxiety of re-dislocating, imposing a substantial resource burden. Dislocation and revision for dislocation are associated with poorer outcomes,” the investigators said.

With DM-THR, the small ball is encased in a much larger plastic ball, creating two articulations, the researchers said. “This design improves stability by increasing the range of motion of the joint before dislocation.”

In this superiority study, 1,566 participants (mean age 76.1 years, 64.5 percent women) were randomized 1:1 to receive either a DM-THR or a standard THR. Seventeen participants crossed over from THR to DM-THR, 35 did from DM-THR to THR, and 48 underwent hemiarthroplasty. The most common type of replacement was cemented THR (80 percent), followed by hybrid THR (15 percent).

“Duality provides evidence that DM-THR reduces the risk of the most common surgical complication for patients with a displaced femoral neck fracture treated with a THR,” the researchers said.

“[These data are] important for clinicians and policymakers alike, and implementation into clinical practice is both feasible and desirable to improve care of older adults with this common and hazardous injury,” they added.