Superior trunk versus interscalene brachial plexus block in humerus surgery: a randomised controlled trial

Ultrasound (US)-guided interscalene (IS) block is a commonly performed block for shoulder and humerus surgery. Though it provides excellent analgesia, it is associated with hemidiaphragmatic paralysis and dyspnoea. Superior trunk (ST) block has been described, wherein the local anaesthetic is deposited around the ST block (formed by fusion of C5 and C6 nerve roots). This study aimed to determine whether ST block provides similar analgesic efficacy with lower incidence of diaphragmatic paresis in patients undergoing proximal humerus surgery.

A total of 62 patients scheduled to undergo unilateral internal fixation (plating) for proximal or mid shaft humerus fracture were randomised to 2 groups. Patients in group I received US-guided ST block while those in group II received US-guided IS block. Both groups received 15 mL of 0.5% bupivacaine. Diaphragmatic excursion was noted at baseline and after 30 minutes after the block. Postoperatively, the numerical rating scale score and requirement of opioids were documented.

The incidence of complete/incomplete paresis was statistically significantly lower in the ST group. Thirty eight percent of the patients (11) had complete paresis in the IS group, compared to none in the ST group. Partial paresis was observed in 62% of patients in the IS block group and 19% in the ST block group ( P < 0.001). The percentage reduction of movement was significantly higher in the IS group vs. the ST group ( P < 0.001). There was no difference in pain scores or the amount of opioid consumption between groups.

ST block provides similar analgesia to IS block for proximal/mid humerus surgery with better preservation of diaphragmatic function. This could be a viable alternative in patients with compromised respiratory functions scheduled for such surgery.