Biometric study of the relationships between palmar neurovascular structures, the flexor retinaculum and the distal wrist crease

During surgical exposure of the carpal tunnel it is possible to injure the neurovascular structures closely related to the flexor retinaculum, such as the superficial palmar arch and the communicating branch between the ulnar and median nerves. Because of the importance of these structures and with the purpose of increasing knowledge of anatomical details concerning to the ir location, a biometric study was performed on the retinaculum and the com municating branch, and between the communicating branch and the distal wris t crease, as well as between the retinaculum and the superficial palmar arc h. We dissected 56 hands from 28 Brazilian formalin-preserved cadavers of b oth sexes (24 male) at the Federal University of Sao Paulo-Escola Paulista de Medicina, Brazil. The communicating branch was observed in 96.4% of case s and the superficial palmar arch in 78.6 %. The communicating branch was f ound between the common palmar digital nerve of the 4th interosseous space (from the ulnar nerve) to the homonymous nerve of the 3rd interosseous spac e (from the median nerve). In males, the distance between the distal wrist crease and the site where the communicating branch originates from the ulna r component had an average of 33.9 +/- 5.5 mm on the right side and 30.2 +/ - 8.2 mm on the left. The distance between the distal wrist crease and the junction of the communicating branch with the common palmar digital nerve o f the 3rd interosseous space was 43.6 +/- 6.9 mm on the right and 40.2 +/- 6.2 mm on the left side. Conversely, in 14.8 % of cases (1 female)? the com municating branch was observed to emerge from the common palmar digital ner ve of the 3rd interosseous space. The distance between the retinaculum and the superficial palmar arch in the axial line of the 4th metacarpal bone wa s on average 7.3 +/- 4.3 mm on the right and 8.3 +/- 3.5 mm on the left sid e. At the same level, the distance between the retinaculum and the communic ating branch was 6.2 +/- 3.7 mm on the right side and 5.1 +/- 2.8 mm on the left. These results can be used as a reference during surgical procedures in the palmar region.