Anatomical study of the motor branches of the median nerve to the forearm and guidelines for selective neurectomy

The median nerve is responsible for the motor innervation of most of the muscles usually involved in upper limb spasticity. Selective neurectomy is one of the treatments utilized to reduce spasticity. The purpose of this study was to describe the variations of the motor branches of the median nerve in the forearm and draw recommendations for an appropriate planning of selective neurectomy. The median nerve was dissected in the forearm of 20 fresh cadaver upper limbs. Measurements included number, origin, division, and entry point of each motor branch into the muscles. One branch for the pronator teres was the most common pattern. In 9/20 cases, it arose as a common trunk with other branches. A single trunk innervated the flexor carpi radialis with a common origin with other branches in 17/20 cases. Two, three or four branches innervated the flexor digitorum superficialis, the first one frequently through a common trunk with other branches. They were very difficult to identify unless insertions of pronator teres and flexor digitorum superficialis were detached. The flexor digitorum profundus received one to five branches and flexor pollicis longus one to two branches from the anterior interosseous nerve. There is no regular pattern of the motor branches of the median nerve in the forearm. Our findings differ in many points from the classical literature. Because of the frequency of common trunks for different muscles, we recommend the use of peroperative electrical stimulation. Selective neurotomy of flexor digitorum superficialis is technically difficult, because the entry point of some of their terminal branches occurs just below the arch and deep to the muscle belly.