Background and objectives Although regional analgesia is considered an important component of optimal pain management, use of peripheral nerve blocks for total hip arthroplasty remains controversial. Since the obturator nerve innervates the anteromedial part of the joint capsule, we hypothesized that an obturator nerve block would decrease the opioid consumption after total hip arthroplasty.

Methods In this single center, prospective, triple blinded study, we randomly allocated 60 patients undergoing total hip arthroplasty under opioid-sparing total intravenous general anesthesia to a preoperative obturator nerve block or a sham block (placebo group) using 20 mL of ropivacaine 0.2% or saline, respectively. All patients received a multimodal analgesic regimen with non-opioid analgesics including periarticular local infiltration analgesia. The primary outcome was the intravenous opioid consumption in the post-anesthesia care unit.

Results Median (IQR) intravenous oxycodone consumption in the post-anesthesia care unit was 4 (2, 7.5) mg in the obturator nerve block group and 3 (0, 4) mg in the placebo group (p=0.05). There were no differences in pain scores between groups in the first 24 hours except at arrival on the surgical ward with significant higher pain scores in the placebo group (p=0.03). The ability to stand up and walk within 24 hours was comparable between groups as was the time to first walk (180 (90, 720) vs 240 (120, 780) min for the obturator nerve block and placebo groups, respectively; p=0.62).

Conclusions Obturator nerve block did not improve postoperative opioid consumption after total hip arthroplasty performed under general anesthesia with a multimodal analgesic regimen.

Trial registration number NCT04085640.