Reduced Ropivacaine Volume with Perineural Dexamethasone in PENG Block for Total Hip Arthroplasty: A Randomized Controlled Trial

Background/Objectives: The pericapsular nerve group (PENG) block is increasingly used as part of multimodal analgesia for total hip arthroplasty (THA). However, standard high-volume local anesthetic regimens may impair motor function. The addition of perineural dexamethasone could allow for volume reduction while maintaining analgesic efficacy and minimizing quadriceps weakness. This study evaluated whether adding dexamethasone to a low-volume PENG block prolongs analgesia, reduces opioid consumption, maintains pain control, and preserves motor function compared to a standard-volume PENG block. Materials and Methods: In this randomized controlled trial (NCT06470334), 60 adult patients undergoing THA via the direct superior approach received either a standard-volume PENG block with 20 mL of 0.2% ropivacaine (PENG group) or a low-volume block with 10 mL of 0.2% ropivacaine plus 4 mg of perineural dexamethasone (PENG + DEX group). The primary outcome was time to first rescue opioid. Secondary outcomes included total 48-h opioid consumption (oral morphine equivalents), pain scores (numeric rating scale, NRS) at rest and during movement, and quadriceps muscle strength at predefined postoperative intervals. Results: The PENG + DEX group demonstrated a significantly longer time to first opioid administration (15.0 ± 1.5 h vs. 9.1 ± 1.7 h; p < 0.0001) and reduced total opioid consumption within 48 h (2.3 ± 3.1 mEQ vs. 5.0 ± 4.4 mEQ; p = 0.0120). Pain scores were similar at 4 h but significantly lower in the PENG + DEX group at 8, 12, and 24 h postoperatively (all p < 0.01). Quadriceps strength was fully preserved in both groups at all assessed timepoints (p > 0.9999). Conclusions: The addition of perineural dexamethasone to a low-volume PENG block provides longer-lasting analgesia and reduces opioid requirements without compromising pain control or quadriceps function. This approach may improve the safety and efficacy of regional anesthesia in THA.