The John Charnley Award: A Randomized Controlled Trial of Dual Mobility and Single Bearings for Patients at High Risk of Dislocation Following Primary Total Hip Arthroplasty.

BACKGROUND

This multicenter randomized controlled trial sought to determine if dual-mobility (DM) bearings reduce dislocations in patients at high-risk for instability undergoing primary total hip arthroplasty compared to single bearing (SB) femoral heads.

METHODS

A total of 555 patients undergoing primary posterior approach total hip arthroplasty were randomized to DM (n = 271; 42 mm mean effective head, range 36 to 55) or SB heads (n = 284; 28 mm [n = 2], 32 mm [n = 42], 36 mm [n = 168], 40 mm [n = 61], 44 mm [n = 11]). High-risk criteria included the following: prior lumbo-sacral fusion (n = 170) or other inclusions (age ≥ 75 years , preoperative combined flexion-adduction-internal rotation ≥ 115°, substance abuse, inflammatory arthritis, neuromuscular disorder, removal of hardware, cognitive impairment, acute displaced femoral neck fracture, and kyphosis/scoliosis; n = 385). There were 28 patients (5.0%) lost to follow-up before 90 days, leaving 527 patients followed for a median of 23 months (range, 3.0 to 87.2).

RESULTS

There were two dislocations in the DM group and six in the SB group (0.7 versus 2.1%, P = 0.29). There was no difference in 2-year dislocation-free survivorship between cohorts (DM: 99.0 versus SB: 97.6%; P = 0.63). There were 16 hips revised (DM: 2.2 versus SB: 3.5%; P = 0.45), with no difference in 2-year all-cause revision-free survivorship (DM: 97.5 versus SB: 96.4%; P = 0.53). Infection was the most common revision indication (two DM [0.7%] versus five SB [1.8%]). There were no differences in patient-reported outcome measures at any time point (P > 0.05).

CONCLUSION

In this multicenter randomized controlled trial, DM bearings were associated with a threefold reduction in dislocation risk, but given the lower than anticipated overall dislocation rate, this difference did not reach statistical significance. Further follow-up is required to capture late dislocations or instability.