Close-range stereophotogrammetry and coupled stress analysis as tools in the development of prosthetic devices

The combination of molding at physiologic pressures, close-range stereophotogrammetric processing, geometric smoothing, finite element analysis, leaflet thickness measurements, and a knowledge of leaflet properties have provided a description of asymmetric geometry and stress patterns within a normal human aortic leaflet which are consistent with anatomic observations. A predominantly circumferential, tensile pattern of stress resultants was found. The higher values of stress resultants coincide with thinner regions of the leaflet. And those in a coronary leaflet. A design stress magnitude of 80 Gm/mm2 for a long pressure of 110 mm Hg, based on the actual thickness of the leaflet, was considerably greater than that previously reported in the literature. Those responsible for device development in the future must consider the mechanical properties and asymmetric geometries in design. Future generation devices will depend on the ability of the designer and the fabricator to incorporate features of asymmetry, anisotrophy, and deformation characteristics which match those of living tissue. Through such efforts more durable devices will result.