Anterior vs posterior approaches to suprascapular nerve block in arthroscopic shoulder surgery: a prospective randomised trial

SSNB is an alternative to interscalene block for shoulder analgesia. We compared anterior and posterior SSNB using 5 mL of local anaesthetic in arthroscopic shoulder surgery. This prospective, randomised, outcome-assessor-blinded, two-arm study enrolled ASA I–III adults aged 18–80 years undergoing arthroscopic shoulder surgery from July 2022 to June 2023. Participants were allocated 1:1 using computer-generated randomisation and sealed envelopes to anterior SSNB (GA) or posterior SSNB (GP). Both groups received ultrasound-guided SSNB with 5 mL of 0.5% bupivacaine. Pain was assessed on a 0–10 visual analogue scale (VAS), where 0 represents no pain and 10 the worst imaginable pain. The primary outcome was 24-h VAS area under the curve (AUC). Secondary outcomes included opioid consumption, change in diaphragmatic thickening fraction (ΔDTF), postoperative nausea and vomiting (PONV), patient satisfaction. Of 64 randomised participants, 60 were analysed (30 per group). The 24-h VAS AUC was lower in GA than GP (27.76 ± 17.18 vs. 55.73 ± 23.06 VAS cm × h; estimated difference − 27.00, 95% CI − 37.00 to − 16.75; p < 0.001), exceeding the prespecified minimal clinically important difference. Pain scores were lower in GA at 30 min, 4 h, 6 h, and 12 h, but not at 24 h after Bonferroni correction. Cumulative opioid consumption was lower in GA at 30 min and 4 h (both p = 0.001; estimated differences − 1.50 mg, 95% CI − 2.00 to − 0.50, and − 4.50 mg, 95% CI − 8.47 to − 2.00). Although DTF decreased significantly within GA, the between-group difference in ΔDTF was not significant (estimated difference − 6.47%, 95% CI − 15.02 to 2.09; p = 0.076). Patient satisfaction was higher ( p < 0.001) and PONV lower ( p = 0.021) in GA. No serious block-related adverse events occurred; one urticarial rash and one chest pain episode were recorded. In arthroscopic shoulder surgery, anterior SSNB with 5 mL of local anaesthetic may be a useful option, offering lower early pain scores and reduced early opioid consumption than the posterior approach. Given the proximal location of the anterior approach, possible phrenic nerve involvement should still be considered. ClinicalTrials.gov, NCT05442814. Prospectively registered on 18 April 2022 (first posted on 1 July 2022; first participant enrolled on 11 July 2022).