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.