Rheumatoid Arthritis Flares After Total Hip and Total Knee Arthroplasty: Outcomes at One Year

Objective Most patients with rheumatoid arthritis (RA) undergoing total hip arthroplasty ( THA ) and total knee arthroplasty (TKA) have active RA and report postoperative flares; whether RA disease activity or flares increase the risk of worse pain and function scores 1 year later is unknown. Methods Patients with RA were enrolled before THA / TKA . Patient‐reported outcomes, including the Hip disability and Osteoarthritis Outcome Score ( HOOS )/Knee Injury and Osteoarthritis Outcome Score ( KOOS ) and physician assessments of disease characteristics and activity (Disease Activity Score in 28 joints [ DAS 28] and Clinical Disease Activity Index), were collected before surgery. Patient‐reported outcomes were repeated at 1 year. Postoperative flares were identified using the RA Flare Questionnaire weekly for 6 weeks and were defined by concordance between patient report plus physician assessment. We compared baseline characteristics and HOOS / KOOS scores using 2‐sample t ‐test/Wilcoxon's rank sum test as well as chi‐square/Fisher's exact tests. We used multivariate linear and logistic regression to determine the association of baseline characteristics, disease activity, and flares with 1‐year outcomes. Results One‐year HOOS / KOOS scores were available for 122 patients (56 with THA and 66 with TKA ). Although HOOS / KOOS pain was worse for patients who experienced a flare within 6 weeks of surgery, absolute improvement was not different. In multivariable models, baseline DAS 28 predicted 1‐year HOOS / KOOS pain and function; each 1‐unit increase in DAS 28 worsened 1‐year pain by 2.41 ( SE 1.05; P = 0.02) and 1‐year function by 4.96 ( SE 1.17; P = 0.0001). Postoperative flares were not independent risk factors for pain or function scores. Conclusion Higher disease activity increased the risk of worse pain and function 1 year after arthroplasty, but postoperative flares did not.