Subpectineal obturator nerve block reduces opioid consumption after hip arthroscopy: a triple-blind, randomized, placebo-controlled trial

Background Hip arthroscopy causes severe pain during the first few hours in the postoperative care unit. This is probably due to the intraoperative stretching of the hip joint capsule. Pain relief requires high doses of opioids which may prolong recovery and may cause opioid-related adverse events. The majority of hip joint capsule nociceptors are located anteriorly. The obturator nerve innervates the anteromedial part of the hip joint capsule. We hypothesized that a subpectineal obturator nerve block using 15 ml bupivacaine 5 mg/mL with added epinephrine 5 μg/mL would reduce the opioid consumption after hip arthroscopy. Methods 40 ambulatory hip arthroscopy patients were enrolled in this randomized, triple-blind controlled trial. All patients were allocated to a preoperative active or placebo subpectineal obturator nerve block. The primary outcome was opioid consumption for the first 3 hours in the postanesthesia care unit. Secondary outcomes were pain, nausea, and hip adductor strength. Results 34 patients were analyzed for the primary outcome. The mean intravenous morphine equivalent consumption in the subpectineal obturator nerve block group was 11.9 mg vs 19.7 mg in the placebo group (p<0.001). The hip adductor strength was significantly reduced in the active group. No other intergroup differences were observed regarding the secondary outcomes. Conclusion We found a significant reduction in the opioid consumption for patients receiving an active subpectineal obturator nerve block. The postoperative intravenous morphine equivalent reduction the first painful 3 hours was reduced by 40% for patients receiving a subpectineal obturator nerve block in this randomized, triple-blind trial. Trial registration number EudraCT database 2021-006575-42.