Effect of the Pericapsular Nerve Group (PENG) Block on Postoperative Pain after Elective Total Hip Arthroplasty: study protocol for a randomized, double-blind, 4-arm factorial trial

Background The pericapsular nerve group (PENG) block has emerged as a promising motor-sparing regional anesthesia technique for hip surgery. However, its definitive role in reducing postoperative pain and opioid consumption following total hip arthroplasty (THA) remains a matter of debate. This study aims to evaluate the analgesic efficacy of the PENG block with and without a lateral femoral cutaneous nerve (LFCN) block. Methods This is a prospective, randomized, double-blind, controlled trial conducted at a single academic center. A total of 168 patients undergoing elective primary THA under general anesthesia will be randomly assigned to one of four groups: (1) low-volume PENG + LFCN block; (2) high-volume PENG + LFCN block; (3) high-volume PENG + sham LFCN; (4) sham PENG + sham LFCN. The primary outcome is the numeric rating scale (NRS) pain score at rest four hours postoperatively. Secondary outcomes include opioid consumption, motor strength, sensory block success, incidence of PONV, patient satisfaction, and adverse events. Discussion This trial will provide evidence on the optimal volume of PENG block and the additive value of LFCN block in multimodal analgesia for THA. Findings may influence future clinical decision-making on regional techniques for motor-sparing analgesia in hip arthroplasty, particularly in the context of “enhanced recovery after surgery”. Protocol version: 1.0, 13 October 2025 Trial registration: German Clinical Trials Register (DRKS): DRKS00037861