LONGITUDINAL FORCES ACTING AT SIDE-TO-END AND END-TO-SIDE ANASTOMOSESWHEN A KNITTED POLYESTER ARTERIAL PROSTHESIS IS IMPLANTED IN THE DOG

In a previous study, which investigated the tensions at the proximal a nd distal end-to-end anastomoses of a vascular prosthesis, no signific ant differences were found in the longitudinal forces between the two anastomotic sites after different periods of implantation. The present follow-up study was devised to study the longitudinal forces at a pro ximal side-to-end and a distal end-to-side anastomosis using a warp kn itted polyester prosthesis implanted as a canine thoracoabdominal bypa ss. The external surface of the prosthesis contained a specially print ed ''tension indicator'' design, which enabled changes in length to be assessed photographically at the two anastomoses at the time of impla ntation and at sacrifice. The longitudinal force at each sire was then calculated using a relationship obtained experimentally between the t otal longitudinal force and the changes in length of the virgin graft in vitro. The in vitro measurements an the prosthesis were performed u sing a computer-controlled laser calibration system. Although the resu lts showed a tendency toward a gradual loss in longitudinal force at b oth anastomoses over 7 months in situ, statistical analysis showed no significant difference in the longitudinal force at the two anastomoti c sites after any period of implantation. Histopathological and textil e analysis also showed that the characteristics of the prostheses were similar at both anastomotic sites. This does not mean, however, that the intramural stress concentrations experienced by the two sites were the same. While comparing the level of the longitudinal forces measur ed in this study with those observed in the previous thoracic aorta st udy using end-to-end anastomoses, no significant differences were obse rved due to the different types of anastomoses. It would appear that t he longitudinal force is not one of the main etiological factors that cause the formation and localization of anastomotic failure.