The surgical neck of humerus  is most common place of fracture.  Axillary nerve runs the surgical neck with the posterior circumflex humerus artery.

The fracture can cause :  

♣ Sever weakness in abduction of humerus. (Deltoid muscle) 

♣ Weakness in latera rotaion of humerus. (Teres minor muscle)

Also, axillary nerve innervate the superior and lateral arm sensory. Thus, injury to the axillary nerve can cause in parathesia in the area.