Clinical anatomy of the subcutaneous veins in the dorsum of the hand.

Ninety adult upper extremities from human cadavers were used to study the patterns of the subcutaneous veins in the dorsum of the hand, with careful dissection and measurement under magnification. In our series, the distribution of the veins was not symmetrical in the dorsum of the hand. In 83.3% of the cases, the veins were arranged in two groups, radial and ulnar, above the transverse midline of the dorsum. The area between these two groups, corresponding to the proximal halves of the second metacarpal bone, the second intermetacarpal space and the third metacarpal bone, might be called "vein lacking area". Crossing branches of veins were found in all cases. There were on average three crossing branches in each case, and their internal diameters were 0.9 +/- 0.2 mm. This study established that the subcutaneous veins in the dorsum of the hand are arranged in two layers. They communicate freely with the veins in the palmar aspect through the intermetacarpal spaces. The average number of perforating branches was 3.9, and their internal diameters were 1.0 +/- 0.4 mm. The perforating branch in the first intermetacarpal space was wide (internal diameter: 1.8 +/- 0.3 mm) and very constant (appearance rate: 100%). This branch may be the most important communication between the superficial and deep veins. We found the venous values in 70.0% of the perforating branches, which prevent the blood flowing from the dorsum to the palm.