Effect of different liposomal bupivacaine concentrations in ultrasound-guided superior trunk block on postoperative analgesia and mobility: a randomized double-blind controlled trial protocol for shoulder arthroscopy

BACKGROUND: Shoulder arthroscopy frequently causes severe postoperative pain that may impede recovery. Liposomal bupivacaine provides prolonged analgesia, and ultrasound-guided superior trunk block (STB) offers comparable analgesia to interscalene block with a lower risk of hemidiaphragmatic paralysis. However, the optimal concentration of liposomal bupivacaine for STB remains unknown. METHODS: This randomized, double-blind, controlled trial will enrol 282 adult patients scheduled for elective arthroscopic rotator cuff repair. Patients will be randomly allocated (1:1:1) to receive ultrasound-guided STB with liposomal bupivacaine 66 mg (Group A), 44 mg (Group B) or 33 mg (Group C), each diluted to 10 mL. The co-primary outcomes are (1) rest pain Numeric Rating Scale (NRS) score at 48 h post-surgery and (2) cumulative oral morphine milligram equivalents (MME) consumption within 0-48 h after surgery. Secondary outcomes include rest pain NRS scores at 6, 24 and 72 h; motor function assessed by Muscle Balance Scale, Bromage score and American Shoulder and Elbow Surgeons (ASES) score at 6, 24, 48 and 72 h; and Quality of Recovery-15 (QoR-15) score at 24 and 48 h. DISCUSSION: This study will provide evidence on the optimal concentration of liposomal bupivacaine for STB in arthroscopic shoulder surgery, aiming to achieve effective and prolonged analgesia without compromising shoulder mobility.