[Alloplastic tracheal prosthesis with biocarbone. A study of animal experiments (author's transl)]

Experimental bioprosthetic reconstruction of the trachea

We removed the tracheas from sacrificed laboratory animals and subjected this tissue to multi-step chemical processing. This method allowed us to preserve the cartilage and reduce its antigenicity, thus creating a bioprosthesis very similar to the host tissue. By using allogeneic and xenogeneic prostheses so prepared, no signs of immune rejections were seen following heterotopic or orthotopic implantations. The transplanted cartilage remained stable for periods ranging up to 21 weeks in recipient rats, while partial morphologic integrity of the cartilage was seen up to 1 year in pigs. Reepithelialization of the transplant with ciliated epithelium was completed in all specimens 12-24 weeks following surgery. Segmental replacement of up to one third of the whole trachea was possible in rats, whereas similar segmental replacements failed in pigs. We also found that successful reconstruction of window-shaped defects was possible. We consider our tracheal bioprosthesis to be superior to cialit-preserved grafts and also to most other biological reconstruction procedures.

[Regeneration of the trachea following partial or total replacement by synthetic resorbable material (polyglactin 910)]

Though longer distances of the trachea and segments of the bronchi can be resected and the blunts be joined by end-to-end anastomosis, the replacement of parts of the wall of the tracheobronchial tree may become necessary. Alloplastic not absorbable material like silicone was not successful because of its disposition to infections and development of stenosis. Absorbable suture material proved to be suitable in tracheal surgery and it was shown that texture of Polyglactin 910 (Vicryl) could even be used for replacement of the aortic wall. We used weaved tubes of 2.5 mm diameter as prostheses of this material. We partly resected the trachea in the throat of 30 rats and in a microsurgical procedure we replaced in 17 animals the whole circumference by the tube shaped prosthesis and in 13 animals a window in the trachea by a patch, cut from such a prosthesis. By pneumonia or granulation in the anastomosis region 11 rats died or had to be sacrificed untimely. The others survived in several periods up to 10 weeks. At the time of autopsy starting after 3 weeks, a newly formed trachea could be demonstrated, which is covered more and more with respiratory epithelium. By light microscopic and scanning microscopic examinations, the development of a new wall, similar to the normal one, was seen. This wall lacks only mucus glands, but contains structures similar to hyaline cartilage. Our absorbable prosthesis cannot prevent the development of stenosis by overshooting granulation in the early postoperative period, but very soon the material is absorbed and replaced by a structure similar to the normal wall. After biodegradation, problems appear by instability of the new tissue, because of collapsing during inspiration. This problem could be solved by covering the prosthesis by an additional supporting scaffold.