Anterior Suprascapular Versus Interscalene Block for Postoperative Analgesia After Arthroscopic Shoulder Surgery in the Outpatient Setting

Shoulder surgery performed in the outpatient setting can be associated with moderate to severe postoperative pain, especially during the first hours after surgery. Regional anesthesia is commonly used to improve postoperative pain control, reduce opioid use, and support early recovery and safe discharge. The interscalene block (ISB) is widely considered an effective regional anesthesia technique for shoulder surgery, but it may be associated with adverse effects such as diaphragmatic impairment, dyspnea, hoarseness, Horner syndrome, and prolonged upper limb motor block. The anterior suprascapular nerve block (SSNB-A) is a more selective regional anesthesia technique that may provide comparable postoperative analgesia with fewer block-related adverse effects. This prospective, randomized, single-blind, noninferiority trial compares SSNB-A with ISB in adult patients undergoing unilateral shoulder surgery in the outpatient setting. All participants receive general anesthesia and the same multimodal analgesic strategy. The primary objective is to determine whether SSNB-A is noninferior to ISB for postoperative pain control, assessed using the Numeric Rating Scale (NRS). Secondary outcomes include quality of recovery measured with the QoR-15 questionnaire, block-related adverse events, sensory and motor block characteristics, and the need for rescue analgesic medication.

Inclusion Criteria: * Age \> 18 years. * ASA physical status I, II, or III. * Scheduled for unilateral shoulder orthopedic surgery in the outpatient/day surgery setting under general anesthesia. * Surgical procedures may include long head of biceps tenotomy, biceps anchor repair, Bankart procedure, rotator cuff repair with or without biological membrane augmentation, subacromial decompression, acromioplasty, or acromioclavicular stabilization. * Ability to understand the study procedures and provide written informed consent. Exclusion Criteria: * Contraindication to regional anesthesia, including allergy to local anesthetics, infection at the injection site, bleeding diathesis, or other contraindications according to applicable clinical practice recommendations. * Allergy to paracetamol or to any drug used in the multimodal rescue analgesic strategy. * Known neuropathy or sensory/motor deficit in the surgical area or in the territory of innervation of the study blocks. * History of psychiatric or behavioral disorders that may interfere with study participation or outcome assessment. * Severe obesity, defined as body mass index (BMI) \> 40 kg/m2. * Severe chronic obstructive pulmonary disease, GOLD stage III-IV. * Pregnancy. * Known phrenic nerve palsy associated with diaphragmatic paralysis. * Chronic opioid use during the previous 3 months. * Severe chronic pain during the previous 3 months, defined as NRS \> 4. * Non-adherence to the postoperative analgesic protocol.