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

Shoulder surgery in the outpatient setting requires an anesthetic and analgesic strategy that provides effective postoperative pain control while allowing early recovery and safe discharge. Unilateral shoulder procedures may be associated with moderate to severe postoperative pain, particularly during the first 24 to 48 hours after surgery. In this context, regional anesthesia is an important component of perioperative pain management because it can reduce postoperative pain, decrease the need for opioid analgesics, limit postoperative nausea and vomiting, and facilitate early rehabilitation and recovery.

The interscalene brachial plexus block (ISB) is commonly used for postoperative analgesia after shoulder surgery and is considered one of the most effective regional anesthesia techniques for this indication. However, ISB may be associated with block-related adverse effects, including variable phrenic nerve involvement with diaphragmatic impairment, dyspnea, Horner syndrome, hoarseness, and prolonged motor block of the upper limb. These effects may be particularly relevant in the outpatient setting, where delayed discharge, unplanned admission, or reduced quality of recovery may occur if adverse effects persist after surgery.

The anterior suprascapular nerve block (SSNB-A) has been proposed as a regional anesthesia technique for shoulder surgery that may provide effective analgesia while potentially reducing some of the adverse effects associated with ISB. The suprascapular nerve contributes substantially to the sensory innervation of the shoulder. The anterior approach targets the nerve in the supraclavicular region and may also allow local anesthetic spread toward relevant components of the superior trunk region involved in shoulder innervation. Available evidence suggests that SSNB-A may provide postoperative analgesia comparable to ISB in selected shoulder procedures, with a potentially more favorable side-effect profile.

This study is a prospective, monocentric, randomized, single-blind, noninferiority trial comparing SSNB-A with ISB for postoperative analgesia in adult patients undergoing unilateral shoulder surgery in the outpatient setting. Participants are randomized to receive either an ultrasound-guided interscalene block or an ultrasound-guided anterior suprascapular nerve block before surgery. Randomization is performed shortly before the procedure using block randomization in order to ensure balanced allocation between the two study groups.

Eligible participants are adult patients scheduled for unilateral shoulder surgery in the outpatient 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, and acromioclavicular stabilization. Participants are screened according to predefined inclusion and exclusion criteria. Exclusion criteria include contraindications to regional anesthesia, allergy to local anesthetics or study analgesic drugs, known neuropathy or sensory or motor deficits in the surgical area or block territory, severe obesity, severe chronic obstructive pulmonary disease, pregnancy, known phrenic nerve paralysis with diaphragmatic paralysis, chronic opioid use, severe chronic pain, and inability or unwillingness to follow the postoperative analgesic protocol.

Both regional anesthesia techniques are routinely used at the study center and are performed by anesthesiologists experienced in ultrasound-guided upper limb nerve blocks. In the ISB group, the block is performed with the patient in the supine or semi-sitting position, with the head turned away from the surgical side. The brachial plexus is identified between the anterior and middle scalene muscles at the level of the cricoid cartilage using a linear ultrasound probe. An echogenic 21-gauge needle is advanced with an in-plane technique toward the space between the C5 and C6 nerve roots. After negative aspiration, 10 mL of ropivacaine 0.5% is injected in divided boluses to obtain adequate local anesthetic spread.

In the SSNB-A group, the block is performed with the patient in the supine or semi-sitting position, with the head turned away from the surgical side. The superior trunk of the brachial plexus is identified using a linear ultrasound probe, and the suprascapular nerve is visualized in the supraclavicular fossa as it separates from the superior trunk and courses beneath the inferior belly of the omohyoid muscle. An echogenic 21-gauge needle is advanced with an in-plane technique toward the suprascapular nerve. After negative aspiration, 10 mL of ropivacaine 0.5% is injected in divided boluses to obtain adequate spread around the nerve.

All participants undergo general anesthesia according to the study protocol. Intraoperative monitoring includes oxygen saturation, heart rate, noninvasive blood pressure, 5-lead electrocardiography, bispectral index monitoring, end-tidal carbon dioxide, and body temperature. Dexamethasone 0.15 mg/kg is administered intravenously before surgical incision. General anesthesia is maintained with inhaled anesthetics and opioids. Before the end of surgery, paracetamol 15 mg/kg and ondansetron 0.1 mg/kg are administered according to the protocol. After emergence from anesthesia, participants are observed in the post-anesthesia care unit.

Postoperative analgesia is standardized in both study groups. In the post-anesthesia care unit, if postoperative pain is rated as NRS 4 or higher, ketorolac 30 mg intravenously is administered as first-line rescue analgesia. If pain remains uncontrolled after 30 minutes, tramadol 1 mg/kg intravenously is administered as second-line rescue analgesia. Participants are discharged from the post-anesthesia care unit to the day surgery ward when Aldrete discharge criteria are met. During the day surgery stay, participants continue the standardized recovery pathway, including monitoring of vital signs, pain control, mobilization, oral intake, hydration, and spontaneous urination. Additional postoperative analgesia during the ward stay includes oral paracetamol and ibuprofen as rescue therapy according to the study protocol.

At discharge, participants receive instructions for the postoperative multimodal analgesic regimen and the data collection forms. Post-discharge follow-up is performed by telephone at predefined time points in order to assess pain control, adherence to the analgesic regimen, recovery, adverse events, and outcome measures. Quality of recovery is assessed using the QoR-15 questionnaire during follow-up. Postoperative pain is assessed using the Numeric Rating Scale at predefined time points after surgery.

The primary objective of the study is to determine whether SSNB-A is noninferior to ISB in terms of postoperative pain control after shoulder surgery in the outpatient setting. The primary endpoint is postoperative pain measured by the Numeric Rating Scale, with the main analysis focused on the NRS score at 6 hours after surgery. The noninferiority margin is defined as 1.1 points on the 0-to-10 NRS scale.

Secondary objectives include comparison of block-related adverse events, including dyspnea, oxygen desaturation, hoarseness, Horner syndrome, pneumothorax, and neurologic complications; assessment of quality of recovery using the QoR-15 questionnaire at discharge and during postoperative follow-up up to postoperative day 5 and at 30 days; comparison of sensory and motor block characteristics in the relevant dermatomes and myotomes; and comparison of rescue analgesic use within a standardized multimodal analgesic protocol.

Baseline demographic and clinical data are collected before the anesthetic procedures, including age, sex, weight, height, ASA physical status, previous surgery, allergies, current medications, and relevant medical history. Intraoperative and postoperative data are collected according to the study protocol. Participants and postoperative outcome assessors are blinded to group allocation, while the anesthesiologist performing the block is not blinded. Statistical analyses are planned before completion of data collection and are performed by an investigator blinded to treatment allocation.

The planned sample size is 100 participants. The sample size calculation is based on the primary noninferiority analysis of postoperative NRS pain scores, assuming a noninferiority margin of 1.1, an estimated standard deviation of 2, a one-sided type I error rate of 5%, and a type II error rate below 20%. The sample size is increased to account for protocol deviations and exclusions, as the primary analysis is planned according to a per-protocol approach.

The study is conducted in accordance with the principles of Good Clinical Practice, the Declaration of Helsinki, and applicable national and international regulations regarding personal data protection. Written informed consent is obtained from all participants before enrollment.

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.