Late treatment of facial paralysis continues to be a challenge for plastic surgeons. New trends for facial reanimation began with the transfer of neurovascularized muscle flaps. In 2002, Wang described the use of the internal oblique muscle (IOM) flap with a vascular pedicle and multiple neural pedicles for single stage treatment of facial paralysis, besides correcting the buccal and orbital region at the same time8. The objective of this study is to obtain anatomic data of the IOM flap and to evaluate histomorphometry feature of the flap pedicles, as well as considering its employment for reanimation of the paralyzed face.

An anatomical study in twelve fresh cadavers was done totalizing 22 dissected flaps. Blood supply to the IOM is based on three main vascular pedicles: deep circumflex iliac artery, intercostal artery of the 11th rib and the infracostal artery. (fig.1) The proximal portion of the pedicles was submitted to histomorphometric analysis with evaluation of the arterial diameter and its degenerative changes (elastosis, fibrosis and focal thickening). The following parameters were analyzed in this anatomic study: length of vascular and nerve pedicles, thickness of IOM flap, measured in the center of the triangle formed by the three pedicles, minimum size of flap and diameter of artery and its degenerative changes through histomorphometry.

Our anatomic study demonstrated that the mean length of the pedicles of the deep circumflex iliac artery, infracostal and intercostal arteries are, respectively, 10.6cm (±2.4cm), 9.7cm (±2.0), and 9.4cm (±3.13). (fig.2) This data confirms a suitable length of the deep circumflwx iliac artery for microsurgical anastomosis, but the results are different from that reported in Wang’s study. The mean thickness of the flap is 0.79 (±0.15), confirming that it is a thin flap and the transferred volume is small. The histomorphometric study measured the arterial diameters and degenerative changes of the walls.

 The anatomic and histomorphometric study of IOM flap indicated that the length of the infracostal and intercostal pedicles is insufficient, in the majority of cases for correction of paralysis at a single stage (according to Wang the pedicle must be a minimum of 12 cm for the anastomosis in the unaffected hemiface8). The IOM flap can be transferred with a very reduced volume, resulting in little change in facial contour. The incidence of major degenerative changes in arterial pedicles of this flap is low (fig. 3); hence it is safe for microsurgical anastomosis and the diameter of the deep circumflex iliac artery is the largest of the three pedicles, so is the option of choice for vascular anastomosis, followed by the intercostal and lastly by the infracostal.