A study of some properties of a sample of bovine cortical bone using ultrasound

Summary Both collagen fibers and long bone exhibit similar anisotropy in several respects, strongly supporting the concept that the anisotropy of bone has its source in the contained collagen fibers which are parallel to the bone axis in mature adult mammalian bone. Experimental information was obtained for a sample of adult bovine tibia from the midregion of the bone prepared as 22 specimens, 2 mm thick, in three orientations—axial, tangential, and radial—with respect to the measurement of sonic velocity. Thickness, sonic transit time, and weight were obtained for the original wet specimens in 0.15M saline, after dehydration at room temperature, after rehydration, and after demineralization in 0.5M EDTA solution. The average density and volume fractions of water, mineral, and organic components closely matched those reported by Biltz and Pellegrino for bovine bone. The distribution of orientation-dependent properties (velocity, change in velocity, and change in thickness) kept the same pattern in every state, although the intensity of the anisotropy varied. The fractional dimensional changes when samples were dehydrated were greatest in the radial direction and least in the axial, just as for collagen fibers. An almost identical decrease in thickness was observed in magnitude and distribution when the specimens were demineralized. Estimates of the sonic velocity for bone collagen were obtained with the aid of the Lees-Davidson hypothesis. These values often matched the published values for collagen fibers, summarized as follows: -1107-1