JOA - 2026-03-11 - Journal Article
Effects of Ankylosing Spondylitis on Total Knee Arthroplasty Outcomes and Postoperative Manipulation Under Anesthesia Rates.
Gadda MN, Norton JB, Mittal MM, Collett GA, Huo MH, Weinschenk RC
Topics
Key Takeaway
AS patients undergoing TKA showed no increased MUA rates at 90 days (2.36% vs 2.90%), 1 year (3.42% vs 3.95%), or 2 years (3.62% vs 4.08%) compared to propensity-matched non-AS controls, but had higher rates of postoperative anemia (6.44% vs 5.40%) and UTI (4.53% vs 3.47%).
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Summary
This study asked whether AS patients undergoing primary TKA have higher MUA rates due to their chronic inflammatory state and propensity for synovial hypertrophy. Using a national insurance claims database (2010–2020) with 1:5 propensity score matching, 3,512 AS-TKA patients were compared to 17,560 controls. No significant differences were found in MUA, PJI, periprosthetic fracture, aseptic loosening, or dislocation rates, though AS patients had significantly higher postoperative anemia and UTI rates.
Key Limitation
Claims data cannot capture preoperative knee ROM, AS disease activity scores, or biologic/DMARD therapy status, making it impossible to determine whether disease severity or immunosuppression modulates the observed complication rates.
Original Abstract
BACKGROUND
Ankylosing spondylitis (AS) is a chronic autoimmune spondyloarthropathy primarily affecting the spine and sacroiliac joints, with up to 70% of patients developing asymmetric oligoarthritis in lower-limb joints. With the rise in total knee arthroplasty (TKA) among the elderly, more AS patients are undergoing this procedure. This study aimed to assess whether AS patients undergoing TKA have a higher rate of manipulation under anesthesia (MUA) compared to non-AS patients, hypothesizing that AS patients' increased inflammatory state would lead to more synovial hypertrophy, scarring, and stiffness, resulting in a higher need for MUA.
METHODS
We conducted a retrospective analysis using a national insurance claims database, identifying patients who underwent primary TKA from 2010 to 2020. Patients were divided into AS-TKA (who had a preoperative AS diagnosis) and non-AS-TKA groups. Propensity score matching (1:5 ratio) was used to compare outcomes between the groups. Postoperative complications, including MUA, were analyzed using Chi-square tests. Out of 2,055,785 TKAs, 4,131 involved AS patients. After exclusions and matching, the AS-TKA group had 3,512 patients, and the non-AS-TKA group had 17,560.
RESULTS
There were no differences in MUA rates postoperatively at 90 days (2.36 versus 2.90%, P = 0.08), one year (3.42 versus 3.95%, P = 0.14), and two years (3.62 versus 4.08%, P = 0.20). There were no significant differences found in prosthetic joint infection, periprosthetic fracture, aseptic loosening, or prosthetic dislocation rates. However, AS-TKA patients had higher rates of postoperative anemia (6.44 versus 5.40%, P < 0.05) and urinary tract infection (4.53 versus 3.47%, P < 0.05).
CONCLUSIONS
The AS patients undergoing TKA do not demonstrate an increased risk of joint-related complications or MUA compared to non-AS patients within the limits of this claims-based analysis; however, AS patients exhibited higher rates of postoperative anemia and UTIs.