True about peripheral nerve injury in upper limb

The radial nerve is very commonly damaged in the region of the radial (spiral) groove. The common causes of injury are: (i) intramuscular injections in the arm (triceps), (ii) sleeping in an armchair with the limb hanging by the side of the chair (Saturday night palsy), or even the pressure by a crutch (crutch paralysis), and (iii) fractures of the shaft of the humerus. This results in the weakness or loss of power of extension at the wrist (wrist drop) and sensory loss over a narrow strip on the back of forearm, and on the lateral side of the dorsum of the hand. Ref : B D Chaurasia's Human Anatomy , seventh edition , volume 1 , pg. no., 101.