Neovascularity of a tracheal prosthesis/tissue complex

Abstract

Permanent bioincorporation of a microporous tracheal prosthesis will require a stable blood supply to connective tissue supporting an epithelial surface. In experience with over 80 tracheal implants in dogs, we have observed that end-on ingrowth and epithelialization does not occur in the absence of lateral ingrowth, epithelialization is marked by the appearance of a subepithelial network of vessels, and this process must be well advanced by 6 to 8 weeks for long-term stability. These observations were extended by using microangiography to delineate the blood supply of the prosthesis/tissue complex. Six implants of bioelectric polyurethane with 10% gentamicin (3 cm length, 2 cm diameter, 1 to 1.25 mm wall thickness, 60 to 120 mu micropore diameter) were interposed in the dog thoracic trachea and wrapped with an omental pedicle. The aorta was perfused with a barium suspension at elective sacrifice between 10 weeks and 21 months. Radiographs of specimens were correlated with bronchoscopic, gross, and histopathological findings. Neovascularity of the prosthesis/tissue complex can be described in three categories: outer capsule, prosthetic wall, and inner lining. Outer capsule vessels were oriented circumferentially immediately adjacent to the prosthetic wall. They resembled arteries up to 75 mu diameter on microscopy and appeared to develop from the omentum with connections developing to the bronchial circulation. Prosthetic wall vessels up to 75 mu with thin muscular walls were noted to traverse the porous prosthetic wall. The inner lining had a network of subepithelial vessels that connected to the lamina propria vasculature of the native trachea across the anastomoses with vessels up to 120 mu in diameter. We conclude that the omentum provides an immediate blood supply and a base for early connective tissue ingrowth. Epithelialization occurs as early as 3 weeks on the favorable bed, accompanied by vascular connections to the existing lamina propria tracheal vessels. This dual organization of blood supply with connections across the prosthetic wall is probably important to long-term stability of healing.