Fibromyalgia as a Risk Factor for Postoperative Complications Following Total Knee Arthroplasty.

Fibromyalgia is characterized by chronic, diffuse musculoskeletal pain and tenderness, associated with fatigue, sleep issues, brain fog, and depression. The effects of fibromyalgia on total knee arthroplasty (TKA) are yet to be fully understood. Previous analyses looking at patients with fibromyalgia undergoing primary TKA have shown an increased risk of developing postoperative complications; however, all have been conducted without controlling for other risk factors, including opioid use. We conducted a retrospective cohort study using the National Inpatient Sample to identify patients with fibromyalgia undergoing unilateral, primary TKA from 2016 to 2021. Patients with fibromyalgia were matched 1:1 to patients without fibromyalgia, accounting for age, sex, race, ethnicity, insurance, modified Elixhauser comorbidities, smoking, and opioid use. After matching, there were a total of 96,870 (n = 48,435 per group) patients who met the inclusion and exclusion criteria for this study. For those undergoing primary TKA, fibromyalgia was associated with higher rates of postoperative hypotension (3.11% vs. 2.68%, OR: 1.16, p < 0.01), anemia (14.51% vs. 13.60%, OR: 1.07, p < 0.01), atelectasis (0.71% vs. 0.59%, OR: 1.21, p < 0.01), urinary retention (1.28% vs. 1.09%, OR: 1.17, p < 0.01), fluid and electrolyte imbalance (6.46% vs. 5.82%, OR: 1.11, p < 0.01), intestinal obstruction (0.44% vs. 0.23%, OR: 1.95, p < 0.01), constipation (3.59% vs. 3.31%, OR: 1.08, p = 0.01), and delirium (0.58% vs. 0.44%, OR: 1.30, p < 0.01). A higher percentage of patients in the fibromyalgia cohort were not discharged directly home compared with the control (18.1% vs. 15.4%, p < 0.01). This present study showed that patients with fibromyalgia had higher rates of postoperative complications compared with a matched control cohort, even when accounting for opioid use.