Experimental determination of mechanical shear stress about an anastomotic junction.

The present study is undertaken to determine whether the elastic tube model originally developed by Kuchar and Ostrach (Biomedical Fluid Mechanics Symposium, pp. 45-69, 1966) accurately provides a first approximation of the biomechanics of the anastomotic junction. The experimental protocol involves the use of canine carotid arteries as the host vessel and several graft materials including autogenous and prosthetic substitutes. The host artery-graft combinations are perfused in vitro in a pulsatile perfusion apparatus which simulates the natural hemodynamic environment. This apparatus provides accurate dynamic measurements of radial wall motion (measured at various longitudinal increments), associated pressures and rates of fluid flow. These data are then applied to the theoretical model for calculation of anastomotic induced bending stresses. The results indicate that the predictions derived from the elastic model consistently overestimate the measured radial change adjacent to the anastomotic junction. As a result shear stresses based on elastic theory deviate from values derived from a numerical curve fit to the experimental data.