THE ABILITY OF ULTRASOUND VELOCITY TO PREDICT THE STIFFNESS OF CANCELLOUS BONE IN-VITRO

The mechanical status of bones is an important consideration in skelet al pathological conditions such as osteoporosis, which result in fract ure at predominantly cancellous bone sites, Density is a good predicto r of the stiffness and strength of cancellous bone, However, these mec hanical properties are also dependent on the cancellous bone's archite cture, The objective of this work was to investigate the ability of ul trasound velocity to predict the Young's modulus of elasticity of canc ellous bone, The cancellous bone specimens were 20 mm cubes from bovin e femur and 21 mm diameter mediolateral cylinders cored from human cal caneus, Ultrasound velocity (V) and Young's modulus (E) were determine d in three orthogonal directions for the bovine cubes [anteroposterior (AP), mediolateral (ML), and proximodistal (PD)], and mediolaterally in the calcaneus, Apparent density (rho) was determined after the othe r tests, Density alone explains 87.6% of the variance of Young's modul us in human calcaneal and bovine femoral bone tested in the PD directi on only, Velocity, however, explains 95% and a combination of density and velocity 97%. Velocity and stiffness are not random with respect t o the three directions in the bovine specimens, Further, for each cube we obtained the mean of the three values of E and of V, and character ized each value of E and V by their deviation from their mean, There i s an extremely strong positive correlation (r = 0.80) showing that the degree of deviation is consistent for E and V, and of the same sign, These results demonstrate that the velocity of ultrasound in cubes of cancellous bone can give structure-specific information, In particular , knowledge of both density and velocity allows better predictions of stiffness than do density or ultrasound velocity on their own, Because there are noninvasive methods of measuring density that do not depend on ultrasonic measurement the combination of these two measurements p romises, eventually, to give improved assessment of a bone's weakness and liability to facture. (C) 1997 by Elsevier Science Inc. All rights reserved.