Effects of dehydration-induced structural and material changes on the apparent modulus of cancellous bone

Dehydration is known to cause an increase in the elastic modulus of bone tissue. However, it also causes structural changes (i.e. shrinkage) which can themselves significantly alter the mechanical properties, particularly in cancellous bone. The current study attempts to estimate the contribution of these two competing factors to the net change of dehydration on the apparent modulus of bovine cancellous bone. Cylindrical cores from the lumbar vertebrae were tested in tension, while hydrated and again after dehydration. The bone volume fractions (BV/TV) were measured in both conditions. The results indicate that the average overall increase in the apparent modulus after dehydration is 14 ± 14% (mean ± SD), which represents the net effect of a 27% increase in modulus due to increased tissue modulus offset by a modulus decrease of 13% due to reductions in bone volume fraction. These observations underscore the need to consider both structural and material changes when comparing hydrated and dehydrated mechanical behaviour.