EXPERIMENTAL REPRODUCTION OF FREE-FLAP ERRORS - A NEW MODEL OF THROMBOSIS

Surgical errors in the length and orientation of a flap pedicle can re sult in kinks, twists, or tension on the pedicle vessels. When these e rrors occur together with the microvascular repairs associated with fr ee flap transfer, thrombosis and flap failure may be the outcome. A mo del was designed to simulate these events. The rabbit central ear arte ry and vein were dissected and all other tissue connections were sever ed in a near-complete amputation. The artery was transected, shortened by 2 mm, and repaired standardly. The ear was then rotated 360 degree s, twisting the vein around the repaired artery. The ear cartilage was shortened by 6 mm, then sutured, and the skin was closed. In a series of 20 ears, 95% necrosed, 18 from arterial thrombosis and 1 from veno us thrombosis. Several other groups were used in which aspects of the basic model were modified to determine the factors influencing failure . When the arterial anastomosis was not performed and the vascular ped icle was rotated with cartilage shortening, all ears survived; when th e cartilage was not resected in this paradigm, leaving tension on the pedicle, 50% of the ears necrosed from venous thrombosis. In counterpo int, when the artery was repaired without twisting the pedicle, all ea rs survived, whether or not the cartilage was shortened. When the arte ry was repaired without shortening it and with rotation of the ear, 50 % of the ears necrosed when the cartilage was shortened, 40% from veno us thrombosis and 10% from arterial thrombosis; all ears necrosed (of venous thrombosis) when the cartilage was not shortened. These finding s demonstrate the combined effects of a twisted pedicle, microvascular anastomosis, and vascular tension on thrombotic failure. This new mod el offers a clinically relevant experimental method for evaluating the rapies for the prevention of thrombosis-related free flap failure.