Does the presence of a lipped highly crosslinked polyethylene liner affect the survival of total hip arthroplasty implants?

Aims: This study aimed to evaluate the effect of lipped liners (LL) on implant survival in primary total hip arthroplasty (THA), focusing on mechanical complications such as dislocation and aseptic loosening. Given the conflicting evidence on LL performance, we conducted a large-scale registry analysis to clarify their long-term safety and effectiveness compared to flat liners (FL). Methods: We analyzed 15,222 primary THAs performed in 13,989 patients between 1 January 2000 and 31 December 2021, using data from the Emilia-Romagna Registry of Orthopaedic Prosthetic Implants (RIPO). Patients were allocated into two groups: 7,619 received FL and 7,603 received LL. The primary outcome was implant survival, with mechanical complications as key endpoints. Kaplan-Meier survival analysis and multivariate Cox regression were employed to assess the revision risk, adjusted for age, sex, type of stem fixation, femoral head material, and liner design. Results: Overall, no significant difference in revision rates was observed comparing groups when all the causes of revisions were considered (log-rank p = 0.088); at 15 years, cumulative implant survival was 96.9% for FL and 96.4% for LL. Revisions for dislocation (28.2% vs 19.0%) and aseptic acetabular loosening (19.2% vs 13.8%) were more frequent in the LL group. When considering mechanical complications alone, 15-year survival was 98.9% for FL versus 98.1% for LL; a similar trend was observed at 20 years (98.9% vs 96.2%; p = 0.002). In multivariable analysis, LL use was independently associated with an increased hazard of revision (HR 1.53, 95% CI 1.05 to 2.23; p = 0.026). Conclusion: LL use in THA is linked to a higher risk of mechanical complications and implant revision compared to FL. Although LL may provide enhanced stability in select cases, optimal outcomes depend on patient-specific factors and precise implant positioning, warranting a cautious approach to their widespread use.