Pericapsular nerve group (PENG) block at 10 mL vs. 20 mL for postoperative analgesia after total hip arthroplasty: a randomized controlled trial

Abstract Background The pericapsular nerve group (PENG) block is increasingly used for analgesia in hip-related procedures. However, the optimal local anesthetic volume remains unclear. This randomized non-inferiority trial aimed to compare the analgesic efficacy of 10 mL versus 20 mL PENG block after total hip arthroplasty, hypothesizing that the lower volume would provide non-inferior analgesia. Methods In this single-center randomized controlled non-inferiority trial, 50 patients undergoing hip replacement surgery received an ultrasound-guided PENG block with 0.25% bupivacaine, either 20 mL ( n = 25) or 10 mL ( n = 25). Postoperative analgesia was provided using morphine patient-controlled analgesia. Pain scores at rest and during movement were assessed at predefined time points up to 24 h postoperatively. The primary outcome was the NRS pain score at rest 1 h after surgery. Secondary outcomes included opioid consumption, quadriceps muscle strength, postoperative nausea and vomiting, and patient satisfaction. Results There were no significant differences between groups in opioid-related side effects, quadriceps muscle weakness, patient satisfaction, or length of hospital stay. Non-inferiority analysis demonstrated that the median differences in NRS scores between groups remained within the predefined non-inferiority margin of 1 NRS point at all assessment time points. Non-inferiority of the 10 mL PENG block was confirmed for the primary outcome. Conclusions A 10 mL PENG block provides postoperative analgesia non-inferior to a 20 mL volume without increasing opioid consumption or motor weakness, suggesting that lower volumes may be sufficient and potentially safer after total hip arthroplasty. Trial registration ClinicalTrials.gov, NCT06166602. Registered on December 04, 2023. Retrospectively registered (study start date July 30, 2023).