Introduction: Shoulder arthroscopy is associated with significant postoperative pain. Interscalene brachial plexus block (ISBPB) provides excellent analgesia but frequently causes hemidiaphragmatic paralysis (HDP) and respiratory impairment. Cervical erector spinae plane block (ESPB) has been proposed as a possible alternative approach, but its comparative efficacy, safety, and anatomical spread remain uncertain.
Methods: In this randomized non-inferiority trial, 70 patients undergoing arthroscopic shoulder surgery received cervical ESPB or ISBPB with 20 ml 0.375% ropivacaine. The primary endpoint was resting visual analog scale (VAS) pain at 6 h. Secondary outcomes included static and dynamic VAS, diaphragm ultrasound, respiratory function, handgrip strength, opioid use, adverse events, and satisfaction.
Results: The median between-group difference in resting VAS at 6 h was 0 (range 0-1), meeting the non-inferiority margin. VAS pain scores were lower with ISBPB at 1 and 3 h at rest (p = 0.008 and p = 0.003) and at 3 and 6 h during movement (p < 0.001 and p = 0.007); however, all 95% confidence intervals for median differences were < 1, confirming non-inferiority of ESPB. Cumulative sufentanil use and rescue analgesia were similar. ESPB was associated with greater diaphragmatic excursion and thickening fraction and a lower HDP incidence (RR 0.2 post-block; 0.4 in the PACU; both p < 0.001). Respiratory declines were smaller with ESPB for FVC (5.8% vs. 14.8%; p < 0.001), FEV₁ (4.9% vs. 18.8%; p < 0.001), MIP and MEP (both p < 0.001). Handgrip strength was better maintained and Horner syndrome was less frequent (8.6% vs. 34.3%; p = 0.018). Other adverse events and patient satisfaction were similar between groups.
Conclusions: In this low-risk study population, cervical ESPB met the predefined non-inferiority criterion for postoperative analgesia compared with ISBPB and was associated with less diaphragmatic and respiratory impairment. However, cervical ESPB should not be considered risk-free, and further anatomical, dose-finding, and clinical studies are needed before any broader clinical role can be defined.
Trial registration: ClinicalTrials.gov identifier no. ChiCTR2200060019.
Keywords: Diaphragm; Erector spinae plane block; Interscalene brachial plexus block; Postoperative pain; Randomized controlled trial; Shoulder arthroscopy.
© 2026. The Author(s).