ARE REGIONAL VARIATIONS IN BONE-GROWTH RELATED TO MECHANICAL-STRESS AND STRAIN PARAMETERS

A three-dimensional finite element analysis was used to quantify the p atterns of mechanical stresses within the rabbit distal femur growth p late, and test the hypothesis that these patterns are correlated to me asured patterns of bone growth rates. This investigation of normal dev elopment is the first step toward improving our understanding of the r ole of mechanical factors in bone growth abnormalities. Rabbits from f ive age groups ranging from 1 to 42 days were evaluated, and four diff erent loading conditions were analyzed, representing specific time poi nts in the normal gait cycle. Finite element models generated directly from micro-computed tomography images of the distal femurs identified regional variations in stress and strain parameters, similar to the v ariations in bone growth rates measured using fluorochrome labeling. A linear regression analysis supports the hypothesis that high compress ive stresses are correlated with lower bone growth rates. However, for the loading conditions considered in this study, the variations in me chanical stress and strain parameters explain no more than 15% of the overall variations in bone growth rates. The greatest variations in bo th growth rates and mechanical stresses were present in the anterior f rontal plane from the 42 day age group, in which correlations between reduced bone growth rates and compressive stresses were much stronger (r(2) up to 0.80). (C) 1998 Elsevier Science Ltd. All rights reserved.