Total knee or hip arthroplasty (TKA and THA, respectively) surgeries are painful procedures, especially for patients with fibromyalgia. Although it is common belief that psychosocial factors contribute to poor outcomes of treatment, the contribution of fibromyalgia to the perception of pain following the procedure is less well known. A group from the Department of Anesthesiology in the Division of Pain Medicine at the University of Michigan Health System led by Chad M. Brummett, MD, conducted a study delving into this unknown and determined that fibromyalgia robustly predicts the outcome of arthroplasty.

“In the multivariate linear regression model predicting change in knee/hip pain (primary outcome), a higher fibromyalgia survey score was independently predictive of less improvement in pain,” wrote Dr. Brummett, in the article, “Fibromyalgia Survey Scores Predictive of Poor Outcomes in THA, TKA,” which was published in Arthritis & Rheumatology.

Patients undergoing a single TKA or THA were considered for the study. All patients were given a self-reported questionnaire assessing widespread body pain via the Widespread Pain Index (WPI) and comorbid symptoms via the comorbid Symptom Severity (SS) scale. When added together, these two scores gave a total fibromyalgia survey score with possible values of 0 to 31. A WPI score of greater than 7 and an SS score of greater than 5 or a WPI score between 3 and 6 and an SS score greater than 9 qualified patients as fibromyalgia positive. Finally, pain was quantified using three descriptive scores, an anxiety scale, and recorded use of painkillers.

Compiling the results for the 464 patients with 6-month data showed that for every one-point increase in fibromyalgia survey score, patients’ odds to failure increased by 17.8%. Failure was considered not meeting the threshold of 50% improvement in knee/hip pain. Patients with higher fibromyaliga survey scores had higher rates of failure and higher scores for overall body pain.

Interestingly, only 6% of patients were categorized as having fibormyalgia when entering the study, yet the fibromyalgia score was highly predictive. “This single, simple-to-administer measure was a powerful predictor of a poor outcome and was the only preoperative phenotypic measure to consistently show predictive utility across the different outcome domains,” wrote Dr. Brummett. “As such, the measure may have value in screening for appropriateness for arthroplasty in the clinical setting.” Patients may be advised to seek alternative treatment options or receive more aggressive anti-pain measures following surgery.