Low-Volume Versus Standard-Volume Pericapsular Nerve Group Block with and Without Dexamethasone for Postoperative Analgesia After Total Hip Arthroplasty: A Randomized Controlled Trial

Background: The pericapsular nerve group block provides motor-sparing analgesia after total hip arthroplasty, but the optimal injectate volume and the role of dexamethasone remain unclear. Methods: In this prospective, randomized, quadruple-blinded trial, 120 patients undergoing total hip arthroplasty under spinal anesthesia were allocated to receive ultrasound-guided pericapsular nerve group block with 20 mL or 10 mL of 0.2% ropivacaine, with or without 4 mg dexamethasone. The primary outcome was time to first rescue opioid within 24 h. Secondary outcomes included opioid consumption, pain scores, quadriceps strength, inflammatory markers, and safety. The study was designed as a superiority trial and was not powered to assess non-inferiority between volume groups. Results: Dexamethasone significantly prolonged time to first rescue opioid (hazard ratio 0.08, 95% confidence interval 0.04–0.16; p < 0.0001). Injectate volume had no significant effect on the primary outcome (p = 0.13), and no interaction between dexamethasone and volume was observed. Total opioid consumption at 48 h was lower in patients receiving dexamethasone (mean difference −3.88 mg oral morphine equivalents; p < 0.0001). Pain scores were consistently lower with dexamethasone, while injectate volume had no effect. Quadriceps strength was preserved in all groups. No nerve injury or clinically relevant hyperglycemia was observed. Conclusions: Dexamethasone improves analgesic efficacy of the pericapsular nerve group block after total hip arthroplasty. Reducing injectate volume from 20 mL to 10 mL did not significantly affect the analgesic outcomes; however, the study was not designed to assess non-inferiority. These findings support a strategy of volume optimization in regional anesthesia.