Abstract

Although interscalene brachial plexus block provides effective analgesia for arthroscopic shoulder surgery, a subset of patients develops a marked increase in pain as the block resolves. Advances in the understanding of the brachial plexus sheath have led to wider use of intraplexus and extraplexus injection techniques; however, their comparative effects on rebound pain remain unclear. In this prospective, randomized, double-blind clinical trial, patients aged 18–65 years with ASA physical status I–II undergoing arthroscopic shoulder surgery under ISB with sedation were enrolled. Patients were randomly assigned to receive ultrasound-guided intraplexus ISB or extraplexus ISB using a total of 20 mL of 0.5% bupivacaine. Rebound pain was operationally defined as the onset of severe pain (numerical rating scale [NRS] ≥ 7) following an initial phase of satisfactory analgesia (NRS ≤ 3) coinciding with resolution of the block. Among the 94 enrolled participants, outcome data from 85 patients were available for analysis. Rebound pain occurred more frequently in patients receiving the intraplexus approach than in those treated with the extraplexus technique (37.2% vs. 16.7%). In addition, rebound pain duration was shorter and Quality of Recovery-15 scores on postoperative day 1 were higher in patients receiving the extraplexus approach. Although sensory and motor block onset was delayed with the extraplexus technique, paresthesia occurred more frequently in the intraplexus group. No meaningful differences were observed between groups with respect to postoperative pain intensity or rescue analgesic use. Overall, the extraplexus ISB technique appears to attenuate rebound pain and support better early postoperative recovery, offering a favorable safety profile.

Key words: Interscalene brachial plexus block, arthroscopic shoulder surgery, rebound pain, extraplexus injection, intraplexus injection