Short-term total hip replacement outcomes in ankylosing spondylitis.

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.