Serval Factors Contribute to Prevalent Low Back Pain in Rheumatoid Arthritis Patients

For patients with rheumatoid arthritis (RA), the prevalence of dysfunctional low back pain (LBP) is influenced by multiple factors such as vertebral fractures, higher body mass index (BMI), age, and longer disease duration, according to Japanese researchers in a study published in European Spine Journal.

In this cross-sectional study, from August 2015 to March 2016 researchers queried 1,276 (mean age, 64.6) RA outpatients from Nagaoka Red Cross and Niigata University Hospital in Japan, using the Roland-Morris Disability Questionnaire (RQD) to address the functional-dysfunctional state criterion. They then compared clinical variables such as medical status, disease activity, bone mineral density, and spinopelvic alignment parameters between patients with and without dysfunctional LBP. At the initiation of the survey, researchers canvassed for the following demographic characteristics, variables, and medications: age, sex, BMI, weight and height, age at RA onset, disease duration, serum level of matrix metalloprotease (MMP)-3, visual analog scale (VAS) score for LBP, disease activity score in 28 joints-CRP (DAS-28CRP), history of surgery, daily corticosteroid use, methotrexate (MTX) use, and biological agents (BIO) use.

LBP Caused by Several Components

The survey results showed that dysfunctional LBP occurred in 419 of the 1,276 patients (32.8%). On univariate analysis, notable differences were present in most variables except sex, body weight, C-reactive protein (CRP) level, and prevalence of BIO agent users between patients with and without LBP. Moreover, a multivariate logistic regression analysis unveiled factors associated with dysfunctional LBP in RA patients are BMI (OR=1.116; P<0.001), onset age of RA (OR=1.020; P=0.020) disease duration of RA (OR=1.43; P<0.001), MTX use (OR=0.609; P=0.007), vertebral fractures (OR=2.189; P=0.001), vertebral endplate and/or facet erosion (OR=1.411; P=0.043), DAS-28CRP (OR=1.587; P=0.001), pelvic tilt (OR=1.023; P=0.019), and sagittal vertical axis (SVA, OR=1.007; P=0.043).

Limitations

Although revealing, the authors noted that the study had its limitations.

“We did not evaluate the influence of psychological factors,” they wrote. “Among the various complications of RA, depression is the most common, affecting approximately 15% of RA patients.”

Secondly, they noted that they studied the surgical history of joints, but not joint lesions and lower extremity alignment.

“Several studies indicated that hip lesion and leg length alignment had played an important role in the occurrence of LBP in non-RA patients.” they added. “[Additionally], dysfunctional threshold of RDQ>4 was provided by a report in the general population, not in RA patients. Thus, it is unknown whether this criterion is applicable to RA patients.”

The researchers wrote in their conclusion that strict “control of the body weight and disease activity in RA patients with MTX and avoiding spinopelvic malalignment by preventing vertebral fractures are important.”