The vast majority of comparative analyses of bone form focus on external or midshaft cross-sectional shape of whole bones. Bones, however, are more morphologically complex than their external form alone would suggest, comprising two fundamentally different tissue types, a compact cortical bone shell and, particularly in the epiphyses of long bones and the bodies of vertebrae, carpals, and tarsals, a non-random, three-dimensionally complex network of trabecular bone filling. This highly patterned trabecular tissue has been believed since mid 1800s to preserve records of the trajectories of principal stresses through the skeleton, but it has proven difficult to study structure/function relationships in trabecular bone due to its enormous architectural and mechanical complexity and the inherent difficulties in documenting the loads experienced by and hence the stress trajectories through a joint.
