IMPACT OF OFFSET POLYETHYLENE LINERS ON ACETABULAR COMPONENT LOOSENING: AN AOANJRR REGISTRY-BASED ANALYSIS

Abstract Background Restoring native hip biomechanics is essential for the long-term success of total hip arthroplasty (THA). Lateralized (offset) acetabular liners were developed to increase global offset and improve soft-tissue tension, but their effect on implant fixation and revision risk remains uncertain. Methods A retrospective cohort study was conducted using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). All primary conventional THAs for osteoarthritis performed between 2012 and 2022 using uncemented acetabular components with highly cross-linked polyethylene (HXLPE) liners were included. Procedures were categorized as lateralized liners (LL) or standard liners (SL). The primary outcome was revision for any reason; secondary outcomes included revision for loosening and acetabular loosening. Cumulative percent revision (CPR) was estimated with the Kaplan–Meier method, and Cox proportional hazards models were used to compare groups after adjusting for age, sex, BMI, ASA score, and surgical approach. Results A total of 68,435 primary THAs were analyzed, including 1,182 LL and 67,253 SL procedures. Revision for any reason occurred in 3.21% of LL and 2.44% of SL cases. At 9-year follow-up, CPR was 4.1% (95% CI 2.8–6.0) for LL and 3.5% (95% CI 3.2–3.7) for SL. The adjusted hazard ratio for revision was 1.15 (95% CI 0.83–1.60, p=0.386), indicating no significant difference between groups. Revision for acetabular loosening was rare and comparable (0.17% LL vs 0.12% SL). Conclusion In this large registry-based study, lateralized liners did not increase the risk of revision or loosening compared with standard liners. Despite being more frequently used in younger, male patients and in association with the posterior approach, lateralized liners demonstrated equivalent mid-term survivorship, supporting their safe use to optimize hip biomechanics without compromising implant fixation. Keywords: Total hip arthroplasty; Lateralized liner; Offset liner; Acetabular loosening; Implant survivorship; AOANJRR; Highly cross-linked polyethylene