Comparison of Shoulder Field Anesthesia (SFA) with Interscalene Block (ISB) for Analgesia After Arthroscopic Shoulder Surgery: A Randomized Noninferiority Trial.

BACKGROUND: An interscalene brachial plexus block (ISB) is commonly used for analgesia after shoulder surgery but is associated with neurologic and respiratory complications, including hemidiaphragmatic paralysis. Surgeon-performed shoulder field anesthesia (SFA) is a landmark-guided, phrenic nerve-sparing technique that may provide effective analgesia with fewer complications. The purpose of this study was to compare SFA with ISB for pain control after arthroscopic shoulder surgery. We investigated whether SFA would provide noninferior analgesia as measured by cumulative 48-hour postoperative pain scores.

METHODS: In this randomized trial, patients undergoing arthroscopic shoulder surgery were assigned to SFA or ISB. Postoperative pain was assessed using the numeric rating scale (NRS) at 2, 4, 8, 24, and 48 hours. Patient satisfaction was assessed at 48 hours. Other secondary outcomes included opioid consumption, hospital stay, and block-related complications.

RESULTS: Eighty patients (mean age, 47.7 ± 15.7 years; 53 men) completed the study. All patients were classified as White; 80% were of Middle Eastern ethnicity. Baseline characteristics were comparable between the SFA and ISB groups. The primary outcome analysis demonstrated a mean difference in the cumulative 48-hour NRS pain score of -0.824 (ISB - SFA), with a 95% confidence interval of -1.853 to 0.206. The upper limit of the confidence interval remained below the prespecified noninferiority margin of 1.5 NRS points, demonstrating noninferiority of SFA. ISB provided lower pain scores during the early postoperative period (4 to 8 hours), and pain scores converged thereafter. Hospital stay was shorter in the SFA group. Opioid consumption, patient satisfaction, and oxygen desaturation rates were similar between groups. Two cases of Horner syndrome and 1 respiratory event requiring intensive care occurred in the ISB group; none occurred in the SFA group.

CONCLUSIONS: SFA was noninferior to ISB for the prespecified cumulative 48-hour pain end point. ISB provided superior pain relief during the first 4 to 8 hours, but SFA offered a lung-sparing alternative with similar cumulative opioid requirements and patient satisfaction, fewer clinically apparent block-related complications, and a shorter hospital stay. These findings support a risk-benefit framework to guide individualized analgesic selection.

LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.