Tracheal transplantation: defining the vascular territory of the canine cranial thyroid artery

The management of long-segment tracheal stenosis remains an unsolved clinical problem that has significant implications for the survival of some patients and the quality of life of others. However, recent advances in microvascular tissue transfer may allow tracheal transplantation to be used as a treatment option. Studies in dogs have demonstrated that the reanastomosis of the cranial thyroid artery (CTA) after the transplantation of a short segment of trachea sustains cartilage viability. However, the distal perfusion zone of the CTA within the canine trachea has not been described. Hence it is unclear what length of trachea can be safely harvested, with use of the CTA as the donor artery, without risking ischemia of the distal trachea. This study determined the perfusion territory of the CTA by use of latex or dye infusion via the thyroid branches of the CTA. Findings in five perfusion-fixed cadaver mongrel dogs (8 to 12 kg) were studied. In each dog, both common carotid arteries were dissected and the CTAs identified. The right CTA was ligated and the left common carotid artery was ligated cranial to the CTA. The left common carotid artery was perfused for 10 minutes under 100 mm Hg pressure with black india ink/saline solution (20:1000 ml) or with blue latex solution. Perfusion territories were determined by grossly and microscopically measuring the region of stain in the endolaryngeal and endotracheal airways. The results demonstrated that up to 18 ipsilateral rings of the canine trachea are perfused after injection of dye under physiologic pressure into the CTA. Contralateral staining was also noted, but to a lesser degree. These results suggest that the canine CTA may perfuse, on average, a 16- to 17-ring tracheal segment.