The anatomy of the Berrettini branch: implications for carpal tunnel release

Dissections were performed in 100 fresh cadaver palms to determine the frequency with which superficial palmar communication between the median and ulnar nerves occurs and to what extent it might incur iatrogenic injury during endoscopic carpal tunnel release.

Superficial palmar communication between the median and ulnar nerves was present in 81% of the dissected hands. Superficial palmar communication, also known as the Berrettini branch, has been classified into four distinct types by Ferrari and Gilbert. Twelve hands were classified as Group 1 (communication in an oblique course from the ulnar to the median nerve originating >4 mm above the distal margin of the transverse carpal ligament [TCL]), 16 hands were classified as Group 2 (communication parallel to the distal margin of the TCL), and 53 hands were classified as Group 3 (communication in an oblique course from the ulnar nerve to the third common digital nerve, originating below the distal margin of the TCL). No hand fit the Group 4 classification (atypical communication).

The Berrettini branch can be considered a normal anatomical finding. In 28% of the hands in this study, the branch was proximal to the edge of the distal ligament and, therefore, prone to iatrogenic injury in both one-portal and two-portal endoscopic surgery.