Association between pericapsular nerve group (PENG) block and postoperative inflammatory indices and analgesic outcomes in total hip arthroplasty: a randomized controlled trial.

Abstract

Background: Total hip arthroplasty (THA) induces a pronounced postoperative inflammatory response that contributes to pain, increased opioid requirements, and delayed recovery, particularly in older adults. Although the pericapsular nerve group (PENG) block provides effective analgesia, its impact on systemic inflammation remains insufficiently defined.

Methods: In this prospective, randomized, quadruple-blinded controlled trial, patients aged ≥ 60 years undergoing elective unilateral THA performed under spinal anesthesia were randomized (1:1) to receive an ultrasound-guided PENG block with ropivacaine or a sham block. The primary outcome was the neutrophil-to-lymphocyte ratio (NLR) at 12 h postoperatively. Secondary outcomes included platelet-to-lymphocyte ratio (PLR) at 12, 24, and 48 h, postoperative pain scores, time to first opioid administration, and cumulative opioid consumption within 48 h.

Results: Sixty patients completed the study (30 per group). Baseline inflammatory markers were comparable between groups. At 12 h, NLR was significantly lower in the PENG group than in the control group (5.98 ± 1.42 vs. 9.60 ± 1.83; adjusted p < 0.0001), with sustained reductions at 24 h (2.47 ± 0.77 vs. 5.71 ± 1.74; adjusted p < 0.0001) and 48 h (1.84 ± 0.71 vs. 3.53 ± 1.08; adjusted p < 0.0001). PLR was also significantly lower in the PENG group at all postoperative time points (all adjusted p < 0.0001), with a significantly different postoperative trajectory between groups over time. The PENG block significantly prolonged time to first opioid administration (15.0 ± 1.5 vs. 9.3 ± 1.7 h; p < 0.001) and reduced cumulative 48-h opioid consumption (13.2 ± 2.7 vs. 20.8 ± 3.2 mg; p < 0.001). Pain scores at rest and during mobilization were consistently lower in the PENG group throughout the first 24 h.

Conclusions: In older adults undergoing THA, the PENG block was associated with lower postoperative inflammatory indices, improved pain control, and reduced opioid requirements. Because NLR and PLR are indirect inflammatory markers, these findings should be interpreted cautiously and viewed as associative rather than mechanistic. Further studies are required to determine whether these physiological differences translate into improved clinical recovery outcomes.

Trial registration: ClinicalTrials.gov (NCT07023107), registered on 8 June 2025.