Total Hip Replacement Outcomes in Ankylosing Spondylitis
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.
Ankylosing spondylitis (AS) is the prototype axial spondyloarthritis, a chronic inflammatory condition affecting the spine and sacroiliac joints, which may be associated with enthesitis, ocular inflammation, and peripheral arthritis. Ankylosing spondylitis of the spine is characterized by inflammation with the potential for subsequent formation of bony syndesmophytes, which may bridge vertebra and result in severe loss of function from spinal rigidity. Ankylosing spondylitis also affects the hips, and up to 25% of patients develop inflammatory arthritis, which may lead to end-stage hip damage. Hip disease in AS is typically seen in those with severe spine disease and is associated with worse functional status, younger age at onset, and persistent active inflammation. Concurrent hip and spine involvement can lead to significant deformity and disability, as patients assume the characteristic flexed hip and flexed knee gait, which may be necessary to maintain forward gaze. Although widespread use of potent disease-modifying drugs has improved overall functional status and quality of life for patients with inflammatory arthritis, benefits in AS have not been as significant as in other diseases such as rheumatoid arthritis.6 This is reflected in the observations that although current rates of total hip replacement (THR) for RA have stabilized and even decreased in some studies, THR rates for patients with spondyloarthritis have increased by 50%.
Total hip replacement is the treatment of choice for advanced hip arthritis, and patients with osteoarthritis (OA) have well accepted improvements after THR. Patients with AS historically report significant improvements in pain and quality of life, as well as satisfaction with THR. However, improvement in function is not clearly described. Previous retrospective studies have compared THR outcomes for AS undergoing THR with AS who have not undergone THR, which are not equivalent groups. Using this comparison group, lower scores on functional measures such as the Bath AS functional index have been reported for the AS who have undergone THR. Hip disease in AS is highly associated with severe spine disease, so benefits from THR may be understated if the presence of back pain is not considered in the analysis. The purpose of this study was to assess 2-year outcomes among contemporary patients with AS undergoing THR compared with matched OA control subjects, controlling for multiple potential confounders, including the presence of back pain.
Abstract and Introduction
Abstract
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.
Introduction
Ankylosing spondylitis (AS) is the prototype axial spondyloarthritis, a chronic inflammatory condition affecting the spine and sacroiliac joints, which may be associated with enthesitis, ocular inflammation, and peripheral arthritis. Ankylosing spondylitis of the spine is characterized by inflammation with the potential for subsequent formation of bony syndesmophytes, which may bridge vertebra and result in severe loss of function from spinal rigidity. Ankylosing spondylitis also affects the hips, and up to 25% of patients develop inflammatory arthritis, which may lead to end-stage hip damage. Hip disease in AS is typically seen in those with severe spine disease and is associated with worse functional status, younger age at onset, and persistent active inflammation. Concurrent hip and spine involvement can lead to significant deformity and disability, as patients assume the characteristic flexed hip and flexed knee gait, which may be necessary to maintain forward gaze. Although widespread use of potent disease-modifying drugs has improved overall functional status and quality of life for patients with inflammatory arthritis, benefits in AS have not been as significant as in other diseases such as rheumatoid arthritis.6 This is reflected in the observations that although current rates of total hip replacement (THR) for RA have stabilized and even decreased in some studies, THR rates for patients with spondyloarthritis have increased by 50%.
Total hip replacement is the treatment of choice for advanced hip arthritis, and patients with osteoarthritis (OA) have well accepted improvements after THR. Patients with AS historically report significant improvements in pain and quality of life, as well as satisfaction with THR. However, improvement in function is not clearly described. Previous retrospective studies have compared THR outcomes for AS undergoing THR with AS who have not undergone THR, which are not equivalent groups. Using this comparison group, lower scores on functional measures such as the Bath AS functional index have been reported for the AS who have undergone THR. Hip disease in AS is highly associated with severe spine disease, so benefits from THR may be understated if the presence of back pain is not considered in the analysis. The purpose of this study was to assess 2-year outcomes among contemporary patients with AS undergoing THR compared with matched OA control subjects, controlling for multiple potential confounders, including the presence of back pain.
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