Tracheal neovascularization: a method involving mobilization of a complete tracheal neovascularized segment using a sternohyoid muscle flap.

Tracheal segmental free grafts always tend to undergo necrosis with consequent occlusion of the airway. Revascularized grafts are impossible to carry out, since the trachea is devoid of a major vascular pedicle that would permit microvascular reconstruction. On the other hand, neovascularized grafts carry a potential for success but have not been sufficiently studied. Neovascularization of a six-ring circumferential tracheal segment (CTS) was studied in dogs using a sternohyoid muscle (SM) flap. Three different procedures were carried out. In group 1 the six-ring CTS was inside a free graft. In group 2 the SM was freed from its proximal connection and rotated to wrap a corresponding six-ring CTS; it was then sutured and left in place for 21 days. After this period it was again approached, and the six-ring CTS was sectioned and sutured back in place, leaving the distally pedicled SM untouched. In group 3 an identical procedure was carried out, but the SM flap was left with a proximally rather than a distally based flap. All surviving animals were followed up for at least 1 year, and the results were analyzed by clinical and tracheoscopic observations and by macroscopic and microscopic studies after the animals were killed. All animals in group 1 died within 18 days; the studies showed necrosis and occlusion of the CTS. In groups 2 and 3 there was no degenerative change of the CTS, whose aspect was close to normal on macroscopic and microscopic examination. We conclude that the free CTS graft is totally inviable. In contrast, neovascularization of the CTS occurs when the segment is first wrapped around with an SM flap. This ensures CTS viability and opens new perspectives for homotransplantation.