A patient’s examination reveals weakness with scapular upward rotation and protraction. Which nerve is MOST likely affected?

• A. Axillary
• B. Subscapular
• C. Suprascapular
• D. Long thoracic

Answer: (D)

Upward rotation and protraction of the scapula are primarily carried out by the serratus anterior. This muscle is innervated by the long thoracic nerve, which originates from C5–C7. When the long thoracic nerve is compromised, serratus anterior becomes weak, so the scapula cannot protract effectively and cannot upwardly rotate properly. This leads to a scapular weakness pattern and often a winged medial border as the scapula loses its stable, protracted position during pushing or reaching.

The other nerves listed innervate different muscles around the shoulder girdle. The axillary nerve mainly affects the deltoid and teres minor, influencing arm abduction and lateral rotation. The suprascapular nerve supplies the supraspinatus and infraspinatus, impacting initial arm abduction and external rotation. The subscapular nerves feed the subscapularis (and teres major), influencing medial rotation and stabilization. None of these pathways best explain weakness in scapular protraction and upward rotation like the long thoracic nerve does, making it the most likely affected nerve.