During shoulder arthroplasty, the surgeon identifies a nerve running along the posterior aspect of the surgical neck of humerus. Injury to this nerve would result in which combination of deficits?
- A Loss of shoulder abduction beyond 15° and sensory loss over regimental badge area ✓
- B Weakness of elbow flexion and lateral forearm numbness
- C Wrist drop and loss of sensation over dorsum of hand
- D Loss of elbow extension and loss of sensation in the radial 3.5 fingers
Correct answer: A. Loss of shoulder abduction beyond 15° and sensory loss over regimental badge area
Explanation
The axillary nerve (C5, C6) winds around the surgical neck of the humerus in the quadrangular space. Its motor branches supply deltoid (shoulder abduction >15° — first 15° by supraspinatus) and teres minor. The superior lateral cutaneous nerve of arm (from axillary nerve) supplies the 'regimental badge area' — a patch over the lateral shoulder. Wrist drop (radial), lateral forearm (musculocutaneous), and elbow extension (radial) are unrelated to the axillary nerve.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.