Adjunctive Muscle Relaxants and Opioid Use Following Total Knee Arthroplasty

The opioid-abuse crisis in the United States is an area of concern within orthopedic practices. Postoperative pain following total knee arthroplasty (TKA) is one of the most common scenarios for opioid prescribing by orthopedic surgeons. Our study explores whether skeletal muscle relaxants (SMRs) may have utility as adjunct treatments to decrease opioid use postoperatively. A retrospective cohort study of patients that underwent elective TKA from July 2012 to July 2020 was performed. Patients prescribed scheduled SMRs while hospitalized were matched in a 1:2 fashion with control patients who were not prescribed SMRs. The primary outcome was Morphine Milligram Equivalents (MME) administered per day postoperatively. Secondary outcomes included pain score, length of stay, and postoperative complications. In total, 157 patients were included: 55 in the muscle relaxant group, and 102 in the control group. Median MMEs administered per day were similar between the two groups (80.2 vs 78.2, p = 0.37). There were no significant differences in adverse events between the two groups. Utilization of SMRs did not significantly decrease opioid use in the immediate postoperative period following TKA in this retrospective cohort. Patients that did receive SMRs did have higher POD1 pain scores and length of admission. All safety outcomes were similar between the groups. Further prospective studies are warranted to appropriately assess the potential of adjunct SMRs use to decrease opioid usage following TKA.