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Background and Aims Hip arthroscopy causes severe pain the first hours postoperative, probably due to the stretching of the hip joint capsule during surgery. Postoperative pain control is often achieved by high doses of opioids. This may cause opioid related adverse events and prolong recovery. The nociceptors in the hip joint capsule are mainly located anteriorly where the obturator nerve innervates the anteromedial part. We hypothesized that a subpectineal obturator nerve block would reduce the postoperative opioid consumption.

Methods Forty ambulatory hip arthroscopy patients were enrolled in this randomized, triple-blind controlled trial approved by the Danish National Center for Ethics. All patients were allocated to a preoperative active or placebo subpectineal obturator nerve block. The primary outcome was opioid consumption the first three hours. Secondary outcomes were pain, nausea, and adductor strength.

Results Thirty-four patients were analyzed. The mean intravenous morphine equivalent consumption was reduced by 40% in the subpectineal obturator nerve block group versus the placebo group, 11.9 mg versus 19.7 mg respectively (p<0.001). See figure 1. The hip adductor strength was significantly reduced in the active group versus the placebo group, with a relative pre-/postoperative adductor strength reduction, 80% versus 38% respectively (p<0.001). No other intergroup differences were observed regarding the secondary outcomes.

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Abstract EP054 Figure 1

Scatter plot of the difference between an active and placebo subpectineal obturator nerve block on consumption of intravenous morphine equivalents during the first three postoperative hours. SOB, Subpectineal Obturator Nerve Block; IV, Intravenous; mg, milligram; Gray/Black diamond, mean opioid consumption

Conclusions A subpectineal obturator nerve block significantly reduced the postoperative opioid consumption by 40% after hip arthroscopy in this randomized, triple-blind trial.