Comparison of interscalene block versus shoulder anterior capsule block for postoperative pain management in rotator cuff surgery: a randomized controlled trial

PURPOSE: Interscalene (ISC) block is the gold standard for regional anesthesia in shoulder surgery but can cause phrenic nerve involvement and motor weakness. The shoulder anterior capsule (SHAC) block has emerged as a potential alternative with motor-sparing benefits. This study compared their analgesic efficacy and motor preservation in arthroscopic rotator cuff repair. METHODS: In a single-center, single-blinded, randomized controlled trial, 46 adult patients (ASA I-III) who underwent arthroscopic rotator cuff repair were assigned to receive either an ultrasound-guided ISC block (n = 23) or SHAC block (n = 23), followed by general anesthesia. The primary outcome was the pain score at the 8th postoperative hour. The secondary outcomes included motor strength, opioid consumption, intraoperative fentanyl requirement, and satisfaction scores. RESULTS: 40 participants (ISC = 20, SHAC = 20) were included in the final analysis. The ISC group had significantly lower pain scores at 1, 2, 4, 8, 12, 16, and 24 h postoperatively (p < 0.05). Motor function was better preserved in the SHAC group during the first 4 h postoperatively, with median (25th - 75th percentile) elbow strength scores of 2.0 (1.25-2.75) at 1 h and 3.0 (3, 4) at 4 h, compared with 0.0 (0-1) and 1.0 (0.25-2.75) in the ISC group, respectively (p < 0.01). However, no significant differences were observed beyond 8 h. Intraoperative fentanyl consumption was higher in the SHAC group (105 100-150 mcg) than in the ISC group (50 50-50 mcg), and 24-hour postoperative fentanyl use was also greater in the SHAC group (140 82.5-170 mcg vs. 5 0-27.5 mcg; both p < 0.001). Patient satisfaction at 24 h was lower in the SHAC group (4.0 3.25-5.0) compared with the ISC group (5.0 5-5; p = 0.001), whereas surgeon satisfaction was similar between the groups. CONCLUSION: Although SHAC block preserves shoulder motor function, it provides less effective analgesia and requires more opioids, which is associated with lower patient satisfaction. TRIAL REGISTRATION (CLINICALTRIALS.GOV): Number: NCT06827912 Date when the study was first posted on ClinicalTrials.gov: 02/10/2025 Date of enrollment of the first research participant: 02/20/2025.