Tracheal anastomoses are, even more so than other sutures, often only possible to prepare under tension and thus in danger of breakage. No information is available regarding native tracheae and freshly sutured tracheae. For this reason, our objective was to examine the tensile strength of native tracheae and compare it with freshly sutured specimens. Fresh tracheae were collected from the local slaughterhouse within 30 min of slaughter. With the help of a suitable holding device, 24 fresh tracheae were mounted on a material testing machine and stretched to breaking point, during which the force and distance required were recorded. The same study was carried out on each 10 freshly anastomosed tracheae using three different suturing techniques. The mean value of the maximum force required for native tracheae was 198 N. With continuous suturing (polypropylene), a mean value of 171 N was attained, and with single interrupted suturing (polydioxanone and polyglactin 910), 123 N, respectively, 108 N. Differences between the groups proved to be highly significant. With respect to the mechanical strain from traction, the continuous suture proved to be statistically identical to native tracheae, whereas single interrupted sutures revealed a considerably lower stability under burden. Therefore, the continuous suture is of advantage in respect of the mechanical strain from traction and the suture protection of tracheal anastomoses. Further studies with differing survival times in vivo with this method provide insight into the stability of tracheal anastomoses during the healing process.

Tissue engineering is an attractive concept for facilitating the transplantation of different tissue types with a low immunogeneity and a well-preserved tissue structure. We examined the influence of treatment with trypsin/ethylenediamine tetraacetic acid (EDTA) on the mechanical properties of tracheae. Fresh sheep tracheae were stored in a trypsin/EDTA solution for various periods of time (24, 46, and 72 h) and their breaking strength was subsequently examined. The results were compared with native trachea. The treatment with trypsin/EDTA results in a considerable reduction of the mechanical stability under load, in this case compared with the tensile strength, that does not correlate with the results obtained from light-optical microscopy. The results from this study reveal that tissue preparation with trypsin/EDTA does not seem to be a suitable method of preparatory treatment of tracheae intended for transplantation.

During the first postoperative days, the stability under load of tracheal anastomoses is slightly lower than that of healthy trachea. This difference is, however, far from those values that can be measured intraoperatively on tracheal anastomoses. Thus, supplementary measures for the mechanical protection against suture line separation do not seem necessary.

The results from this animal experiment reveal-contrary to data published to date-that tracheal homografts are not incorporated but absorbed. They are replaced by scar/granulation tissue that cannot secure the stability of the trachea. Therefore, further experiments with respect to the biocompatability of homografts appear to be necessary.

The necessity of a cervical tracheal replacement arises with thyroid carcinoma, which occasionally infiltrates the trachea extensively, the rare primary tracheal tumors and, sporadically, benign stenoses. In the present study, we used an uncoated porous polypropylene prosthesis as cervical tracheal replacement in sheep. Specifically, we implanted a tracheal prosthesis of polypropylene mesh as a cervical tracheal replacement in five sheep, protecting the airways with self-expanding stents. Healing-in of the prostheses was checked bronchoscopically. The animals were killed after increasing survival times (7, 28, 64, 68, and >90 days), and incorporation of the prosthesis was examined macroscopically, microangiographically and histologically. Although medium-term survival was possible with a sufficiently wide airway, all animals were ultimately euthanized because of complications (airway stenosis, prolapse of prosthesis). Nevertheless, the results show that replacement of the cervical trachea with a polypropylene mesh can be successful under different experimental conditions.