Nerve · Shoulders

Axillary nerve

Nervus axillaris

The axillary nerve supplies the deltoid and teres minor and carries sensation from a coin-sized patch of skin over the shoulder cap — the "regimental badge" area. It reaches them by wrapping backward around the surgical neck of the humerus through the quadrangular space, and that intimate wrap around bone is exactly why it is at risk: a dislocated shoulder or a fracture of the humeral neck stretches or tears it. The tell is a shoulder that cannot be lifted out to the side after an injury, together with a numb patch over the outer shoulder — a check worth making before and after any shoulder is relocated.