Dissection properties and mechanical strength of tissue components in human carotid bifurcations

Carotid artery dissections can be triggered by several factors. The underlying biomechanical phenomena and properties are unclear. This study investigates the dissection properties of 62 human carotid bifurcations using two experimental methods: direct tension and peeling tests. Direct tension tests study the mechanical strength of the tissue components in radial direction, while peeling tests quantify the fracture energy required to propagate a dissection in a tissue. Results show that the interface between the healthy adventitia and media has the highest radial failure stress (132 ± 20 kPa, mean ± SD, n = 25), whereas the lowest value occurs between the diseased intima and media (104 ± 24 kPa, n = 18). The radial tissue strength at the bifurcation is the highest compared with locations that are away from the central region of the bifurcation. Force/width values required to separate the individual layers and to dissect the media in the circumferential direction are always lower than related values in the axial direction, suggesting anisotropic dissection properties. Dissection energies per reference area generated during the peeling tests are also lower for strips in the circumferential direction than for axial strips, and they vary significantly with the location, as shown for the media. Histological investigations demonstrate that interfacial ruptures mainly occur in the media in both types of tests and are 2-5 elastic lamellae away from the external and internal elastic laminae. A remarkably "rougher" dissection surface is generated during axial peeling tests when compared with tests performed in the circumferential direction.