Safe level for harvesting for ulnar and median nerve transfers: a microanatomical and histological study

In selective ulnar and median nerve transfers, donor nerve fascicles should be harvested in an area where motor and sensory fascicles are intermingled to minimize motor or sensory deficits. We aimed to define such an area for ulnar and median nerve harvesting through microanatomical dissection and histology in 12 fresh adult cadaveric upper extremities. Anatomically, we studied the arrangement, localization, and histological features of fascicle groups in two nerves at eight segments of the upper arms. Histological sections were examined to confirm the findings of the anatomical dissections. We found that sensory and motor fascicles were mixed proximally to the third most distal segment of the ulnar nerve and to the fourth most distal segment of the median nerve. We conclude that harvesting a part of the ulnar or median nerve proximal to these levels minimizes donor nerve deficits.