Does Melatonin Improve Subjective Sleep Quality after Total Knee Arthroplasty? A Randomized, Placebo-Controlled Trial.

INTRODUCTION: Sleep disturbance is a common problem following total knee arthroplasty (TKA). The objective of this study was to determine if exogenous melatonin improves sleep quality following primary TKA.

METHODS: A randomized, double-blind, placebo-controlled trial was conducted. A total of 172 patients undergoing unilateral TKA for primary knee osteoarthritis were randomized to receive either 5 mg melatonin (n=86) or 125 mg vitamin C placebo (n=86) nightly for 6 weeks. The primary outcome was the Pittsburgh Sleep Quality Index (PSQI) at 6 weeks and 90 days postoperatively. Secondary outcomes included 6-week and 90-day patient-reported outcome measures (PROMs), morphine milligram equivalents (MMEs) prescribed, medication compliance, adverse events, and 90-day readmissions.

RESULTS: Mean PSQI scores worsened at 6 weeks before returning to the preoperative baseline at 90 days in both groups. There were no differences in PSQI scores between melatonin and placebo groups at 6 weeks (10.2±4.2 versus 10.5±4.4, P=0.66) or 90 days (8.1±4.1 versus 7.5±4.0, P=0.43). Melatonin did not improve the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR), Lower Extremity Activity Scale (LEAS), Visual Analog Scale (VAS) for pain, or Veterans Rand 12 (VR-12) Physical Component Score (PCS) or Mental Component Score (MCS) at 6 weeks or 90 days. Poor sleep quality was associated with worse PROMs at 6 weeks and 90 days on univariate and multivariable analyses, but melatonin did not modify these associations. There were no differences in MMEs prescribed, medication compliances, adverse events, or 90-day readmissions between both groups.

CONCLUSION: Exogenous melatonin did not improve subjective sleep quality or PROMs at 6 weeks or 90 days following TKA. Poor sleep quality was associated with worse patient-reported function and pain. Our results do not support the routine use of melatonin after TKA.