Neural anatomy of the radial forearm flap

Typically the lateral antebrachial cutaneous nerve alone is used to innervate the radial forearm free flap when a sensate flap is required. The authors desired, by means of fresh cadaveric microdissections and by means of local anesthetic injections in living subjects, to map the sensory nerve territories of this flap. Eight radial forearm flaps were elevated and the medial antebrachial cutaneous nerve (MABC), lateral antebrachial cutaneous nerve (LABC), and superficial radial sensory nerve (SRSN) were dissected with the aid of an operating microscope (2.5-10x) and traced to their dermal insertions. In the injection study, the MABC, LABC, and SRSN in eight forearms of 4 subjects were blocked sequentially with 2% lidocaine injections. The resulting sensory deficit from each injection was mapped on the skin and superimposed on the marked radial forearm flap territory. Distribution of the three dissected nerve regions and the sensory deficit after injection were determined by digital images and computer analysis. During flap dissections, mean nerve distributions of total flap area were as follows: LABC, 61.8% (range, 48.3-71.6%); MABC, 33.8% (range, 30.5-38.9%); and SRSN, 34.6% (range, 26.8-44.1%). After nerve block the mapped sensory areas were as follows: LABC, 62.3% (range, 44.5-88.5%); MABC, 19.6% (range, 8.0-35.8%); and SRSN, 19.5% (range, 9.9-26.3%). At least 40% of the total flap area was not innervated by the LABC as identified both by nerve dissection and sensory local anesthetic blockade. By including the LABC, MABC, and SRSN in the radial forearm flap, both the theoretical and the clinically determined useful sensory innervation of the radial forearm flap potentially would be increased.