What are the considerations for suprascapular nerve sparing during a supraclavicular nerve block in patients undergoing shoulder surgery, particularly those with pre-existing nerve conditions or previous surgeries in the region?

Suprascapular Nerve Sparing During Supraclavicular Block

The supraclavicular block does not intentionally target the suprascapular nerve, but inadvertent suprascapular nerve injury can occur as a rare complication, particularly when the block is performed too medially or superiorly near the nerve's anatomic course. 1

Understanding the Anatomic Risk

The suprascapular nerve originates from C5-C6 nerve roots and travels posteriorly through the suprascapular notch to innervate the supraspinatus and infraspinatus muscles, as well as providing sensory innervation to the posterior shoulder capsule, acromioclavicular joint, and subacromial bursa. 2 During supraclavicular block, the needle is typically directed toward the brachial plexus at the level of the first rib, but if the injection is performed too medially or the needle trajectory is misdirected superiorly, there is potential for direct trauma or local anesthetic spread to affect the suprascapular nerve as it branches from the upper trunk. 1

Clinical Evidence of Suprascapular Nerve Injury

Three documented cases of suprascapular nerve palsy following ultrasound-guided supraclavicular block have been reported, all occurring in male patients who initially presented with shoulder pain that resolved, followed by persistent weakness in supraspinatus and infraspinatus muscles that improved but did not fully resolve over time. 1 One case was complicated by concurrent ipsilateral phrenic nerve palsy. 1

Technical Recommendations to Minimize Risk

Use ultrasound guidance for all supraclavicular blocks to visualize the brachial plexus and avoid misdirected needle placement that could injure the suprascapular nerve. 3 The ultrasound allows direct visualization of the needle trajectory and ensures proper placement at the first rib level rather than more superior or medial locations where the suprascapular nerve courses. 3

• Avoid directing the needle too medially toward the scapular spine or too superiorly toward the suprascapular notch region during supraclavicular block placement. 1
• Calculate and use safe doses of local anesthetic to reduce the risk of local anesthetic systemic toxicity and minimize excessive spread that could affect adjacent neural structures. 3
• Consider alternative block techniques when shoulder surgery is planned: axillary or infraclavicular brachial plexus blocks are preferred over supraclavicular blocks when respiratory function preservation is a priority. 3

Alternative Approaches for Shoulder Surgery

For shoulder procedures specifically, interscalene block remains the first-choice regional technique, with combined axillary nerve block and suprascapular nerve block recommended as an alternative only when interscalene block is contraindicated. 4, 5 Supraclavicular blocks provide excellent anesthesia for shoulder surgery but have predictable gaps in posterior arm coverage. 6 However, for shoulder procedures, this missed coverage is typically not clinically significant since the surgical field is primarily innervated by the suprascapular and axillary nerves, which are reliably blocked by interscalene approaches. 6

Special Considerations for High-Risk Patients

In patients with pre-existing nerve conditions or previous shoulder surgeries, the risk-benefit ratio must be carefully evaluated:

• Document baseline neurologic function before performing any regional block in patients with pre-existing shoulder pathology or previous surgeries. 1
• In patients with known suprascapular nerve dysfunction, consider avoiding supraclavicular blocks entirely and opt for more distal approaches (axillary or infraclavicular) that do not risk further injury to the already compromised nerve. 3
• For shoulder surgery in these high-risk patients, direct suprascapular nerve block combined with axillary nerve block provides targeted analgesia without the anatomic proximity risks of supraclavicular approaches. 4, 7

Monitoring and Follow-Up

Thorough testing for block success is essential before proceeding with surgery to minimize the risk of conversion to general anesthesia and to identify any unexpected neurologic deficits early. 3 In the postoperative period, assess shoulder abduction strength (supraspinatus) and external rotation strength (infraspinatus) to detect suprascapular nerve injury, particularly if patients report new-onset shoulder pain followed by weakness. 1