Allograft replacement of the trachea. Experimental synchronous revascularization of composite thyrotracheal transplant.

We describe a method for experimental tracheal transplantation that uses synchronous revascularization based on the blood supply of the related thyroid gland. This study compares the structural integrity and histologic features of nonvascularized tracheal transplants, revascularized thyrotracheal composite allografts, with and without immunosuppression. Eighteen adult beagle dogs underwent tracheal transplant operations with one of the preceding methods. Postmortem specimens were studied macroscopically and histologically, 3 to 28 days postoperatively. Proximal, mid, and distal segments of each graft (twelve-ring segments) were examined microscopically. Nonvascularized tracheal transplants necrosed completely as early as 3 days postoperatively. The vascularized composite thyrotracheal allografts survived for up to 28 days. Six dogs did not receive immunosuppressive agents; tracheal cartilage was preserved in this group, but soft tissue necrosis developed. Six dogs received cyclosporine; tracheal cartilages and all soft tissues remained histologically intact. This difference may be due to early tracheal cartilage ischemia in the nonvascularized group, rejection of the soft tissues in the nonimmunosuppressed group, and viability of all structures in the vascularized and immunosuppressed group. Revascularization of the transplanted trachea with the thyroid arteries maintains the vascularity and hence the viability of the trachea. A reliable substitute for long-segment tracheal resections is finally found. We predict that clinical application of this technique will solve a major problem in the surgery of the airways.