Introduction Ankylosing spondylitis (AS) patients undergoing total hip arthroplasty (THA) face unique challenges, including higher dislocation and complication rates compared to non-AS populations. This study evaluates the long-term incidence and predictors of dislocation in AS patients after THA, with a highlight comparing robotic-assisted and conventional techniques. Methods We retrospectively analysed 80 primary THAs in 49 AS patients (41 male and 8 female) from December 2001 to June 2024. Demographics, surgical factors (robotic vs. conventional THA, prostheses), and radiographic parameters (cup inclination, anteversion) were assessed. Complications including dislocation, loosening, fracture and revision were recorded. Survivorship was analysed using Kaplan-Meier curves, and dislocation predictors were evaluated via Cox regression. Results Mean follow-up was 130 months (range: 14 months–23.5 years). The dislocation rate was 3.8% (3/80), all occurring in conventional THAs (n=67, 4.5%) vs 0% in robotic THAs (n=13). There was one anterior dislocation with cup within Lewinnek safe zone, while the two posterior dislocations were outside the safe zone. Upon regression analysis, no demographic, surgical or radiological parameters predicted dislocation. Other complications included periprosthetic fracture (n=1), periprosthetic joint infection (n=3) and aseptic loosening (n=1). Dislocation-free survivorship was 96.2%, while overall revision-free survivorship was 90% at 10 years’ mean follow-up. Conclusion THA in AS is associated with higher dislocation rate than reported in non-AS patients, with favourable long-term survivorship. Although no specific radiological or surgical factors was predictive of dislocation, it was observed that robotic assistance might prevent THA dislocation in AS. However, large-scale prospective trials are needed to validate its benefits.
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