Introduction The posterior lumbar plexus block (LPB) has been used for decades to provide acute pain management after hip surgery. Unfamiliarity with the technique and its perceived difficulty, potential risks, and possible adverse effects such as quadriceps weakness have limited broader use. The quadratus lumborum block (QLB) has been reported to be effective for postoperative pain control following hip surgery and may thus offer another regional alternative for practitioners. This study hypothesized that the QLB type 3 (QLB3) can produce a non-inferior analgesic effect compared with LPB for primary hip replacement.

Methods This double-blinded, non-inferiority trial randomized 46 patients undergoing primary hip replacement to receive either QLB3 or LPB. Outcomes were assessed on postanesthesia care unit arrival and at postoperative hours 6, 12, and 24. The primary outcome measured was numeric rating scale (NRS) pain score 24 hours after surgery. Secondary outcomes included opioid consumption, presence of quadriceps weakness at first postoperative physical therapy (PT) session, and time to achieve 100 feet of walking.

Results The QLB3 did not cross the non-inferiority delta of 2 points on the NRS pain score (mean difference −0.43 (95% CI −1.74 to 0.87)). There were no significant differences between groups in total opioid consumption at 24 hours or in time to achieve 100 feet of walking. Quadriceps weakness at first PT session was less common with QLB3 (26% vs 65%) and time to perform the block was significantly less with QLB3 (10 min vs 5 min).

Conclusion This trial supported the hypothesis that the QLB3 yields non-inferior analgesia compared with LPB for hip replacement surgery.

Trial registration number NCT03801265.