In humeral fractures, the main nerves in the arm may have been damaged or compressed (by the cast) after manual reduction. The sensory nerve involved in this case is the musculocutaneous nerve which provide sensation in the hands, particularly here in the right hand. Compression by the cast interrupts nerve impulses in the musculocutaneous nerve owing to the loss of sensation and the removal of cast relieves the compression therefore there is regain of sensation.
