]> 2026-07-31T07:52:02+00:00 WBR0496 0 en Thumb adduction The ulnar nerve is responsible for adduction of the thumb. Forearm pronation The radial nerve is responsible for innervating the supinators of the forearm. Arm abduction beyond 15 degrees The deltoid muscle is responsible for arm abduction beyond 15 degrees. The deltoid is innervated by the axillary nerve, which is typically affected by fractures at the surgical neck of the humerus. Wrist extension The radial nerve is responsible for innervating the extensors of the wrist. The radial nerve is damaged by midshaft humeral fractures, such as the one pictured above. Wrist flexion The median and ulnar nerves are responsible for wrist flexion. Anatomy D Musculoskeletal/Rheumatology General Principles 2020-10-28T00:46:01Z 2459150.531956 WBR0496