Deltoid Atrophy

I had an automobile accident in the USA in 1967 when I was 16 years old. As a result, the left shoulder nerve of the Deltoid muscle (please forgive me if I am wording it incorrectly) was severed rendering it inactive.

Although it has been 43 years since, and I can practice any sport, do chin ups, push ups, ride motorcycles, the physical strength as well as the esthetic difference between the two arms is enormous.

I was wondering if there is any chance for a recovery of the nerve through surgery at this juncture.