PREDICTION OF MECHANICAL-PROPERTIES OF THE HUMAN CALCANEUS BY BROAD-BAND ULTRASONIC-ATTENUATION

Broadband ultrasonic attenuation (dB MHz cm(-1), nBUA) was determined for specimens from 20 human calcanei, along with apparent density, ela sticity (Young's modulus), and compressive strength, The calcanei were modified to provide ''whole'' (only soft tissue removed), ''core'' (m ediolateral cores corresponding to in vivo measurement region), ''can' ' (cortical end plates removed from core), and ''def'' (core defatted) samples. The nBUA values for the various modifications were highly co rrelated. The presence of the cortical endplates creates a significant nBUA, probably due to complex phase interactions, nBUA(can) was a goo d predictor of elasticity (R(2) = 75.7%) and strength (R(2) = 73.6%). Apparent density was a better predictor of the mechanical variables th an nBUA, with R(2) values of 88.5% for elasticity and 87.6% for streng th, The morphological anisotropy defined by ''fabric'' for the specime ns was extremely uniform, The coefficient of variation in nBUA (40.5%) and compressive strength (64.4%) was significantly greater than for a pparent density (23.5%) and fabric (6.7%). It is well known that a pow er law relationship exists between apparent density and elasticity or strength in cancellous bone, An interesting finding in this work is th at there also appears to be a power law relationship between nBUA and apparent density, with an exponent of approximately 2, which, in the l ight of clinical implications, warrants further investigation.