The rates of total knee replacement (TKR) continue to rise in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Studies done in previous years suggested that TKR was less successful in improving function in patients with RA than in those with OA. The good news is that a new study finds similar and excellent outcomes for TKR in RA compared with OA in the contemporary era.
"Despite having significantly worse preoperative pain and function, patients with RA undergoing primary TKR have excellent 2-year outcomes, comparable with those of OA patients. A contemporary cohort of patients with RA [with a high prevalence of disease-modifying antirheumatic drug (DMARD) and biological therapy use] no longer lag behind patients with OA. In addition to having worse preoperative pain and function, RA patients had more comorbidities, another known risk factor for poor outcomes in patients with OA after TKR," said first author Susan M. Goodman, MD, Weill Cornell Medical School and Hospital for Special Surgery, New York City.
The study was based on primary TKR cases enrolled between May 1, 2007, and July 1, 2010, in a single-institution TKR registry. Validated RA cases were compared with OA cases at baseline and at 2 years to evaluate pain, function, and quality of life after primary TKR in contemporary cohorts of patients.
"Our hypothesis was that among patients with RA and high DMARD and biologic use who undergo TKR will have comparable outcomes after TKR to those with OA," Dr Goodman stated.
During the study period, 9830 cases of primary TKR were identified; of these, 4456 were eligible for the analysis: 4320 OA cases and 136 validated RA cases. Two-year data were available for 94.7% of the OA cases and 79% of the RA cases. However, the authors included all patients with RA in the analysis, regardless of whether 2-year data were available, to maximize the size of the RA cohort.
At baseline, RA patients were significantly younger than OA patients (63.5 years vs 67.2 years, respectively; P =.0002); were more likely to be women (90% vs 58%; P <.0001); and had significantly lower body mass index (28.5 kg/m2 vs 30.7 kg/m2; P <.0001).
Patients with OA had higher educational status at baseline; 65% of patients with RA had some college education versus 78% of OA patients (P =.015). Fewer RA patients were white (77% vs 86%) and more were African American (12% vs 6%). Patients with RA had significantly more comorbidities than did patients with OA (60% vs 29%, respectively; P <.0001).
Despite having significantly worse Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) pain at baseline, at 2 years patients with RA had similar and excellent WOMAC pain scores compared with patients with OA (13.3 vs 12.7, respectively). Almost all RA and OA patients achieved a clinically meaningful improvement from baseline in WOMAC pain (89% in both cohorts). The percentage with poor WOMAC pain outcomes was similar between patients with RA and those with OA (10% vs 7%, respectively). Among the patients with RA, there was no association between use of a biologic DMARD and poor pain outcome.
A similar pattern was seen for WOMAC function. Patients with RA had significantly worse WOMAC function at baseline than did patients with OA, but at 2 years post TKR, WOMAC function scores were equivalent and excellent for both groups (17.4 vs 14.7, respectively). Almost all patients in both cohorts achieved a clinically meaningful change in WOMAC function from baseline (93% for RA vs 87% for OA).
Satisfaction at 2 years was high in both cohorts, and about 75% in both groups reported "more improvement than I ever dreamed possible" and "great improvement."
Multivariate analyses performed to identify predictors of poor WOMAC pain and poor WOMAC function at 2 years found that RA was not an independent risk factor for poor postoperative pain or function.
Dr Goodman and coauthors say that this is the first study to show equivalent functional outcomes with TKR for both RA and OA patients.
"The improved overall quality of life for RA has been attributed to the widespread use of potent DMARD and biologic agents...among patients with RA. In our cohort, 86.7% of patients with RA undergoing primary TKR were receiving DMARD, biologics, and corticosteroids with no difference in outcomes compared with those not receiving synthetic DMARD or biologics," the researchers wrote.
The authors note that all surgery was performed at a high-volume tertiary referral center, and TKR was performed by surgeons with high RA-specific volume, potentially limiting the generalizability of these findings.
The authors hope that their findings will be used to counsel patients with RA about expectations following TKR.
- Goodman SM, Johnson B, Zhang M, et al. Patients with rheumatoid arthritis have similar excellent outcomes after total knee replacement compared with patients with osteoarthritis. J Rheumatol. 2016;43:46-53.