Background Whether restored mobility bestowed by Total Knee Arthroplasty (TKA) facilitates weight loss in rheumatoid arthritis (RA) patients has not been studied specifically  RA patients may face barriers to post-operative weight loss, such as corticosteroid use and upper extremity arthritis limiting rehabilitation  Clinicians need to counsel RA patients regarding expectations for weight loss after TKA.
Objectives To determine if significant weight loss occurred in overweight and obese RA patients 6-18 months after TKA compared to non-RA patients
Methods All TKAs done at Montefiore Medical Center from 2001-2012 were identified in the electronic medical record. The RA group was defined as patients with at least 2 visits with International Classification of Diseases, Ninth Revision (ICD9) code 714.0 for rheumatoid arthritis and a prescription for ≥1 disease modifying anti-rheumatic drug . The non-RA group was defined as those without RA (714.0), spondyloarthritis (720.x, 696.1, 099.3), inflammatory bowel disease (555.x), or connective tissue disease (710.x). Peri-operative (30 days before to 7 days after) and post-operative (6-18 months after) weight (kg) and body mass index (BMI) (kg/m2) was obtained. Overweight (BMI ≥25-29.9) and obese (BMI ≥30.0) patients were included in the analysis . Bivariate analysis compared baseline characteristics (demographics, Charlson comorbidity index ) and post-operative weight changes of RA and non-RA groups. Multivariate analysis adjusted for gender, ethnicity, race, and comorbidity index. Weight change of >±5% was considered clinically significant .
Results Using defined criteria, 46 RA and 1348 non-RA patients were identified. Of these, 14 (30%) RA and 331 (25%) non-RA were overweight; 31 (67%) RA and 894 (66%) non-RA were obese, p<0.218. Peri-operatively, RA patients were younger, with mean age of 60±10 years, compared to non-RA, 65±10, p<0.002. There was no difference in gender or comorbidity score between the groups. Post-operatively, 20% of RA patients and 20% of non-RA patients lost >5% of their peri-operative body weight, p<0.811. However, 24% of RA and 14% of non-RA gained >5% body weight, p<0.039. In a logistic regression model, age was a predictor of weight gain, p<0.044.
Conclusions A small minority of RA patients lost significant weight 6-18 months after TKA. In contrast, more RA patients gained significant weight, compared to non-RA patients. This data apprises clinicians who counsel RA patients regarding weight loss after TKA. Future studies can identify factors associated with significant weight change.
Stets K, et al. Weight and body mass index change after total joint arthroplasty. Orthopedics. 2010 Jun 9;33(6):386.
Danoff JR, et al. Total Knee Arthroplasty Considerations in Rheumatoid Arthritis. Autoimmune Dis. 2013;2013:185340.
Kim SY, et al. Validation of rheumatoid arthritis diagnoses in health care utilization data. Arthritis Res Ther. 2011 Feb 23;13(1):R32.
Centers for Disease Control and Prevention. Overweight and obesity: defining overweight and obesity. http://www.cdc.gov/nccdphp/dnpa/obesity/defining.htm.
Charlson M, et al. Validation of a combined comorbidity index. J Clin Epidemiol. 1994 Nov;47(11):1245-51.
Overweight, obesity, and health risk. National Task Force on the Prevention and Treatment of Obesity. Arch Intern Med. 2000; 160(7):898-904.
Disclosure of Interest : None declared