Martin-Gruber communicating branch: anatomical and histological study

We dissected 72 upper Limbs of fresh cadavers and found 17 cases with a Mar tin-Gruber communicating branch (23.6%). These were classified into 4 types : type I(n=5, 29.4%): communicating branch between the anterior interosseou s and ulnar nn, type II (n=3, 17.6%): Communicating branch between the medi an and ulnar nn., type III (n=3, 17.6%): Communicating branch between the m uscular branches to the flexor digitorum profundus m., type IV (n=6, 35.3%) : combination of type I or II and type m. At histologic examination the num ber and size of the nerve bundles each communicating branch contained prove d to be very different. In one case of type II only a single nerve bundle w as found. We suggest that the different numbers of nerve bundles innervate different amounts of the intrinsic hand musculature. The communicating bran ch with a single nerve bundle probably innervated only the first dorsal int erosseous muscle.