Study of structure of porous biomaterials. Application of ultrasonic method

It is commonly accepted that, in modelling of the mechanical behavior of bi ological tissues (e.g cortical and trabecular bones) and porous bone implan ts "working" in their natural environment, one should take into account the fact that such biomaterials have a multiphase nature and they are composed of solid porous matrix filled with interstitial fluid. Spatial arrangement of matrix structure strongly influences mechanical properties, transport p henomena, and acoustic waves propagating in saturated biomaterials. The well known two-phase model of dynamics of saturated porous materials de veloped by Blot [1], and extended by other authors includes three pore stru cture macro-parameters (porosity, permeability, and tortuosity). The attenu ation and dispersion of wave velocity predicted by the model results mainly from relative motion of phases. On the other hand, a disease like osteoporosis is identified in both cortic al and trabecular bone by an increase of pore space and related changes in the microscopic pore characteristic that does not appear in Blot's model. S uch micro-quantity (characteristic pore or grain size) plays an important r ole for scattering phenomena at microinhomogeneities in the two-phase porou s materials when the ratio of waves length and average size of pores/grain is not too large. Taking these facts into account, and using the model which incorporates the relative motion of phases and scattering effects, both the micro- and macr o-structure parameters can be determined from wave propagation analysis usi ng the ultrasonic technique and applying wide band spectroscopy.