Effects of Ankylosing Spondylitis on Total Knee Arthroplasty Outcomes and Postoperative Manipulation Under Anesthesia Rates.

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.