[Anatomic study and review of the literature on the Martin Gruber anastomosis].

We dissected 72 upper limbs of fresh cadavers and found 17 cases of the Martin-Gruber anastomosis. The incidence was 23.6%. They can be classified into 5 types. Type I (n = 5, 29.4%): Communication between the anterior interosseous and the ulnar nerves. Type II (n = 3, 17.6%): Communication between the median and the ulnar nerves. Type III (n = 3, 17.6%): Communication between the muscular branches of the flexor digitorum profundus muscle (FDP). Type IV (n = 3, 17.6%): Communication between the anterior interosseous and the ulnar nerves, the muscular branches of the flexor digitorum profundus muscle (FDP) originated from the connection. Type V (n = 3, 17.6%): The anastomotic branch originated from the median nerve and joined the ulnar at two different points as well as connecting with the ulnar branch of the FDP. Through histologic examination, we found the number and size of nerve fascicles which every connection contained to be very different. In one case of type II only one single nerve fascicle was found. We propose the hypothesis that the different amounts of nerve fascicles innervate different amounts of intrinsic hand musculature. The communication which contained one single nerve fascicle only innervate the first dorsal interosseous muscle (FDI).