RELATIONS OF MECHANICAL-PROPERTIES TO DENSITY AND CT NUMBERS IN HUMANBONE

Mechanical properties of cortical and cancellous bone from eight human subjects were determined using art ultrasonic transmission technique Raw computerized tomography (CT) values obtained from scans of the bon es in water were corrected to Hounsfield units. The correlations betwe en CT numbers and mechanical property estimated from cortical bone wer e found to be low (r(2)<0.2), while these relationships for cancellous bone were found to be higher (r(2)>0.6). These results suggest that C T values may be useful in predicting mechanical properties only for ca ncellous bone. Poor correlations were found between modulus in the rad ial or circumferential direction. and modulus in the superior-inferior direction for cortical bone whereas good correlations were found betw een modulus in the anterior-posterior direction or medial-lateral dire ction, and modulus in the S-I direction for cancellous bone. These res ults indicate that modulus in. the radial or circumferential direction could not be predicted from modulus in the S-I direction for cortical bone, but could be predicted for cancellous bone. The predictive capa bilities of linear and power models evaluated for cancellous bone alon e were approximately equal. However, the power function gives a better fit of data at the low and high density values. The specific relation ships, depending on the types of bone, that Predict elastic modulus fr om density and CT numbers were suggested for human, cortical and cance llous bone. These specific correlations may help a number of researche rs develop more accurate models; however, these hypotheses should be p roven by further study.