Clinical anatomy of the internal oblique muscle

In recent years microvascular free tissue transfer has become a well accepted reconstructive technique. The current trend in flap research seems to be the development of more refined flaps to meet specific needs with minimal donor site morbidity. The internal oblique muscle provides a broad, thin, well-vascularized flap which is ideally suited for restoration of contour with excellent aesthetic results. In addition, the iliac crest may be raised in continuity based on the same vascular pedicle, i.e. the deep circumflex iliac vessels. The purpose of this article is to describe the anatomic details necessary for the clinical application of this versatile flap. Thirty specimens of the internal oblique muscle flap were dissected and studied using Microfil injection techniques, including xerograms. In about 80 percent of the flaps, a single ascending branch of the deep circumflex iliac artery (DCIA) enters the undersurface of the muscle, arborizing within the muscle. In the remaining 20 percent, two or three branches enter the muscle separately, originating on the DCIA. The arc of rotation extends into the ipsilateral groin for coverage of exposed femoral vessels, along the pubis and the anterior perineum. The length of the vascular pedicle is to 6 to 7 cm and the vessel diameter is 2.0 to 3.0 mm, making the flap suitable for free tissue transfer.