Contemporary Isolated Bearing Exchange for The Management of Hip Instability Following Primary Total Hip Arthroplasty.

INTRODUCTION: Isolated ball and liner exchanges (IBLE) can be performed to increase hip joint stability, but historical results have been mixed due to a lack of head size options or dual mobility articulations. The purpose of this study was to evaluate the contemporary results of isolated ball and liner exchanges in patients who have instability following primary THA.

METHODS: We retrospectively reviewed 65 primary THAs from 2016 to 2020 with hip instability undergoing isolated ball and liner exchange or conversion to dual mobility articulation. There were 31 men and 34 women who had an average age of 70 years (range, 26 to 92). The mean time to revision from primary was 40.1 months (range, 1 to 120). In 52 cases, IBLE was performed using conventional bearings, while 13 hips were converted to dual mobility. Radiographic factors, including acetabular component orientation, reproduction of hip joint offset, leg lengths, and outcomes such as recurrent instability requiring subsequent revision and patient reported outcome measure (PROM), were recorded and compared.

RESULTS: There were twelve (18.4%) hips that experienced subsequent instability and required another revision (17.3% ball and liner exchange versus 23.1% dual mobility articulation, P = 0.615). The mean time to re-revision for instability was 17.1 months. There were no significant differences in either acetabular component anteversion (P = 0.25) or restoration of hip joint offset (P = 0.87) in patients who required another revision for instability compared to those who did not, respectively. At 1 year, patients undergoing conventional bearing exchange reported higher Hip Dysfunction Osteoarthritis Outcome Score (HOOS) JR (P = 0.002) and Veterans Rand (VR-12) physical component (P = 0.023) scores compared to those who underwent a conversion to dual mobility articulation. Only age > 75 years at the time of surgery was associated with increased risk for dislocation (OR [odds ratio] 7.2, CI [confidence interval] 1.2 to 43.7, P = 0.032).

CONCLUSIONS: Isolated bearing exchanges for instability following THA remained at high risk for subsequent instability. Conversion to dual mobility articulations did not reduce the risk of reoperation.