A Synthetic Form of Cannabinoid Does Not Decrease Opioid Use After Total Knee Arthroplasty: A Prospective, Randomized, Triple-Blind, Placebo-Controlled Study.

Abstract

Self-reported cannabis use in patients undergoing total knee arthroplasty (TKA) has increased since its legalization. Despite endorsement, its efficacy has never been studied in a prospective randomized study in orthopaedic surgery. The purpose of this study was to determine whether a synthetic delta-9-tetrahydrocannabinol (sTHC), dronabinol, decreases opioid use after TKA. There were 163 patients who underwent primary unilateral TKA who were prospectively randomized into receiving dronabinol (2.5 mg twice a day, n = 81) versus a placebo pill (2.5 mg twice a day, n = 82) as an adjunct to pain management. Patients, providers, our statistician, and the research team were blinded to the groups. Patients were cannabis naïve and had drug screening prior to surgery. Patients received our standard perioperative multimodal pain regimen (including opioids) regardless of randomization. The primary outcome was opioid morphine milligram equivalents (MME) at two weeks. Secondary outcomes included self-reported pain, sleep scores, nausea/vomiting, knee range of motion, and patient-reported outcomes. Patients were followed for six weeks after TKA. Statistical significance was accepted at P ≤ 0.05. There were no differences for in-hospital MME consumed (sTHC 40.1 ± 74.8 versus placebo 38.8 ± 76.4, P = 0.901), or in total MME noted at two weeks (sTHC 383.6 ± 309.8 versus placebo 367.6 ± 246.3, P = 0.717). Self-reported pain (P = 0.581; 0.710), hours of sleep per night (P = 0.103; 0.140), and nausea/vomiting (P = 0.689; 0.158) showed no differences between the groups at two and four weeks. No differences in patient-reported outcome measures at six weeks were noted between groups. There were no drug- or placebo-related complications were noted in either group. Despite enthusiasm for cannabis after orthopaedic surgical procedures, this sTHC does not appear to limit opioid intake after primary TKA. Based on these data, THC may offer no benefit for patients after TKA.