Dominant trabecular patterns of the calcaneus are aligned with the principal stress flow during standing

The calcaneus plays a critical role in bearing loads during body support or locomotion. In this study, the manifestation of Wolff´s law of trabecular bone adaptation in the calcaneus has been analyzed. For this purpose, finite element (FE) analysis of the foot during standing was elaborated. Orientation of the principal stress flow through the calcaneus was compared with the trabecular alignment in cadaveric calcaneal specimens, by fitting second-order polynoms to real and FE-predicted trabecular paths and calculating their derivation around the calcaneal cortex. The dominant trabecular patterns observed in cadaveric sagittal specimens of the calcaneus could be classified into four groups; subsequent numerical simulations showed that the dorsal-plantar oriented and posterior oblique trabecular paths are aimed to support compressive stresses, while the antero-posteriorly directed and anterior oblique groups act to bear tension. Insertion angles of real trabecular paths into the calcaneal cortex did not differ significantly from simulations (maximal difference of 13 degrees). This suggests that the trabecular patterns of the calcaneus are mainly shaped by the isostatics (static principal stress flow) developing during the standing posture. The present modeling approach can be utilized to explore effects of abnormal alterations in the isostatic flow on the microarchitecture of the calcaneal trabeculae.