Axillary Nerve and Quadrangular Space

During a difficult shoulder dislocation reduction, a 35-year-old man develops acute loss of sensation over the lateral aspect of the shoulder and upper arm, along with weakness of shoulder abduction. The axillary artery remains palpable and intact. Which anatomical relationship explains this nerve injury?

A 35-year-old male presents to the emergency department following a fall from a ladder with a suspected anterior shoulder dislocation. On examination before reduction, the structure marked **A** (axillary nerve) is tested. Which of the following clinical findings would indicate injury to the structure marked **A**?