Ultrasound-Guided Infraspinatus-Teres Minor Interfascial Block versus Interscalene Brachial Plexus Block for...

This randomized non-inferiority trial was designed to verify whether ultrasound-guided infraspinatus-teres minor interfascial block (ITMB) could produce non-inferior postoperative analgesia in adult patients undergoing arthroscopic shoulder surgery compared with ultrasound-guided interscalene brachial plexus block (ISB), while also comparing the early respiratory safety profiles and postoperative adverse events of the two techniques.

This trial adopted a two-arm parallel-group design with blinding for participants and all outcome assessors. A total of 82 eligible patients were randomly assigned 1:1 to receive either ITMB (n=41) or ISB (n=41) with 25 mL 0.375% ropivacaine for each nerve block. Two participants in the ITMB group were excluded from the per-protocol (PP) analysis due to intraoperative conversion to open surgery and unplanned intensive care unit admission, leaving 39 ITMB patients and 41 ISB patients for primary PP analysis; intention-to-treat (ITT) analysis covering all 82 randomized patients was additionally conducted to validate robustness. The primary prespecified outcome was 24-hour postoperative total oxycodone consumption, with a predefined non-inferiority margin of -5 mg (ISB minus ITMB). Non-inferiority was established if the lower limit of the 95% confidence interval (CI) for the between-group mean difference was no less than -5 mg. Secondary endpoints comprised the maximum 11-point resting NRS pain score within 24 h, incidence of rebound pain, and rescue analgesia requirements. Safety endpoints included dyspnea, diaphragmatic paralysis, Horner's syndrome, and postoperative nausea and vomiting.

PP analysis showed the mean 24-hour oxycodone consumption was 11.26 (SD 4.38) mg in the ISB group (95% CI 9.89 to 12.65) versus 10.92 (SD 3.48) mg in the ITMB group (95% CI 9.79 to 12.05), with a between-group mean difference of 0.34 mg (95% CI -1.42 to 2.11, P<0.001). The lower bound of the 95% CI (-1.42 mg) substantially exceeded the pre-specified non-inferiority margin of -5 mg, satisfying the non-inferiority criterion (one-sided non-inferiority P<0.001). ITT analysis yielded consistent non-inferiority results (mean difference 0.26 mg, 95% CI -1.46 to 1.99, P<0.001). For secondary pain outcomes, the median worst resting NRS score within 24 h was significantly lower in the ITMB group [3.0 (IQR 3.0-4.0)] than the ISB group [4.0 (IQR 3.0-7.0), median difference 1.0, 95% CI 0 to 1.0, P<0.001]. ITMB also brought significantly lower rebound pain rate (2.6% vs 26.8%, P=0.006) and less frequent rescue analgesia requirements (7.7% vs 29.3%, P=0.016). Safety outcomes revealed significantly lower early hemidiaphragmatic paralysis and dyspnea in the ITMB group: hemidiaphragmatic paralysis occurred in only 2.6% of ITMB patients vs 90.2% of ISB patients (P<0.001); dyspnea incidence was 2.6% (ITMB) vs 19.5% (ISB, P=0.016); Horner's syndrome was absent in the ITMB group while occurring in 29% of ISB patients (P<0.001). Postoperative nausea and vomiting rates were comparable between two groups (P=0.655). No severe block-related complications such as nerve injury, local anesthetic systemic toxicity or pneumothorax were observed in either group.

Ultrasound-guided ITMB provided non-inferior 24-hour postoperative opioid analgesia compared with ISB and reduced the incidence of early hemidiaphragmatic paralysis in patients undergoing arthroscopic shoulder surgery. The comparable total 24-hour oxycodone consumption reflected distinct time-dependent analgesic profiles, with ISB providing greater analgesic benefit during the early postoperative period, whereas ITMB demonstrated more sustained analgesic effects during the later postoperative period.

This trial was registered at the Chinese Clinical Trial Registry (ChiCTR2400084716). Date of registration: May 23, 2024.