Biomechanical effects of intraspecimen variations in trabecular architecture: A three-dimensional finite element study

Trabecular architecture is considered important in osteoporosis and has bee n quantified by a variety of mean parameters characteristic of a whole spec imen. Variations within a specimen, however, have been mostly ignored. In t his study, the theoretical effects of these intraspecimen variations in arc hitecture on predicted mechanical properties were investigated through a th ree-dimensional finite element parameter study that simulated variations in trabecular thickness in a controlled manner. An irregularly spaced lattice of different sized rods was used to simulate trabecular bone in three dist inct volume fraction ranges, representing young, middle-aged, and elderly v ertebral bone. Beta distributions (a type of non-normal distribution) of tr abecular thickness with coefficients of variation of either 25%, 40%, or 55 % were applied to the rods in each model, and 225 simulations of uniaxial c ompression tests were performed to obtain modulus values. Percent modulus r eductions of 22% and 43% were predicted when the intraspecimen coefficient of variation in trabecular thickness was increased from 25% to 40% and from 25% to 55%, respectively, for models of equal volume fraction. Furthermore , this trend was predicted to be independent of volume fraction. We conclud e, therefore, that consideration of the intraspecimen trabecular thickness variation in conjunction with volume fraction may improve the ability to pr edict trabecular modulus compared with use of volume fraction alone. Furthe r, the model suggests that if age, disease, or drug treatments increase tra becular thickness variation, this may be detrimental to mechanical properti es. (C) 1999 by Elsevier Science Inc. All rights reserved.