Background: While rates of total hip replacement (THR) in spondyloarthritis are increasing, contemporary outcomes are not well described.
Objectives: This study analyzes 2-year outcomes in a contemporary cohort of ankylosing spondylitis (AS) patients undergoing THR.
Methods: A case-control study was performed using data from an institutional arthroplasty registry. Validated AS cases were matched 4:1 by age and procedure to patients with osteoarthritis (OA). Data were obtained prior to surgery and at 2 years. Multiple imputation techniques were performed to avoid systematic bias due to missing data.
Results: Thirty eligible AS cases were identified between May 2007 and February 2010. Ankylosing spondylitis cases had worse American Society of Anesthesia class (P < 0.001) and more comorbidities (P = 0.02) compared with OA. Ankylosing spondylitis had worse preoperative lower-extremity Western Ontario and McMaster Universities Arthritis Index pain (46.8 vs 55.4; P = 0.03), function (43.0 vs 55.1; P = 0.04), and general health status measured as SF-12 (Short-Form Health Survey) physical component scale (PCS) score (29.6 vs 36.0; P < 0.001), however, there was no difference at two years in pain (89.4 vs 92.5; P = 0.23) or function (83.9 vs 90.1; P = 0.04). Physical component scale score remained significantly worse (41.2 vs 50.1; P < 0.001). Better preoperative SF-12 PCS score significantly decreased the risk of a poor pain outcome (odds ratio, 0.06; 95% confidence interval, 0.01-0.40). Overall satisfaction was high.
Conclusions: Although patients with AS in a contemporary cohort have more comorbidities and worse physical function prior to THR, they achieve similar gains as OA. In a multivariate regression controlling for multiple potential confounders including back pain, only preoperative health status measured as SF-12 PCS score was a significant risk factor for a poor 2-year pain. Among contemporary patients, AS is not an independent risk factor for poor THR outcomes.Take-Home Message Patients with AS have significant improvement in pain and function after THR.Poor preoperative function and low-back pain are not risk factors for poor THR outcomes for patients with AS.Despite improvements, low SF-12 PCS scores indicate persistent limitations due to health.