Effects of external beam irradiation on the TRAM flap: An experimental model

The rat model of the transverse rectus abdominis musculocutaneous (TRAM) fl ap was used in the present stud! to determine the effects of external beam radiation on myocutaneous flap histology and pathophysiology. A total of 57 adult Sprague-Dawley rats underwent a TRAM procedure. A pilot study with 1 7 animals was first performed to determine proper radiation dosages, and th e remaining 40 rats were then used in the definitive study. in half of the definitive e study group, the flaps were subjected to fractionated doses of external beam radiation, whereas tile other half served as controls. Six w eeks after the last radiation dose, all animals were killed and tile naps w ere harvested for mechanical assessment and histopathologic evaluation. All TRAM flaps survived in both groups. The irradiated and nonirradiated flaps were minimally distinguishable in viscoelastic properties, as well as by h is topathologic examination. Growth of the flap in the irradiated animals w as significantly diminished (48 percent average surface area increase in ir radiated flaps, versus 92 percent increase in nonirradiated flaps, P < 0.05 ). These findings suggest that the myocutaneous flap is relatively resistan t to some of the known adverse affects of radiation on living tissues.