Trabecular architecture of the great ape and human femoral head

<jats:title>Abstract</jats:title><jats:p>Studies of femoral trabecular structure have shown that the orientation and volume of bone are associated with variation in loading and could be informative about individual joint positioning during locomotion. In this study, we analyse for the first time trabecular bone patterns throughout the femoral head using a whole‐epiphysis approach to investigate how potential trabecular variation in humans and great apes relates to differences in locomotor modes. Trabecular architecture was analysed using micro<jats:styled-content style="fixed-case">CT</jats:styled-content> scans of <jats:italic>Pan troglodytes</jats:italic> (<jats:italic>n</jats:italic> = 20), <jats:italic>Gorilla gorilla</jats:italic> (<jats:italic>n</jats:italic> = 14), <jats:italic>Pongo</jats:italic> sp. (<jats:italic>n</jats:italic> = 5) and <jats:italic>Homo sapiens</jats:italic> (<jats:italic>n</jats:italic> = 12) in <jats:sc>medtool</jats:sc> 4.1. Our results revealed differences in bone volume fraction (<jats:styled-content style="fixed-case">BV</jats:styled-content>/<jats:styled-content style="fixed-case">TV</jats:styled-content>) distribution patterns, as well as overall trabecular parameters of the femoral head between great apes and humans. <jats:italic>Pan</jats:italic> and <jats:italic>Gorilla</jats:italic> showed two regions of high <jats:styled-content style="fixed-case">BV</jats:styled-content>/<jats:styled-content style="fixed-case">TV</jats:styled-content> in the femoral head, consistent with hip posture and loading during two discrete locomotor modes: knuckle‐walking and climbing. Most <jats:italic>Pongo</jats:italic> specimens also displayed two regions of high <jats:styled-content style="fixed-case">BV</jats:styled-content>/<jats:styled-content style="fixed-case">TV</jats:styled-content>, but these regions were less discrete and there was more variability across the sample. In contrast, <jats:italic>Homo</jats:italic> showed only one main region of high <jats:styled-content style="fixed-case">BV</jats:styled-content>/<jats:styled-content style="fixed-case">TV</jats:styled-content> in the femoral head and had the lowest <jats:styled-content style="fixed-case">BV</jats:styled-content>/<jats:styled-content style="fixed-case">TV</jats:styled-content>, as well as the most anisotropic trabeculae. The <jats:italic>Homo</jats:italic> trabecular structure is consistent with stereotypical loading with a more extended hip compared with great apes, which is characteristic of modern human bipedalism. Our results suggest that holistic evaluations of femoral head trabecular architecture can reveal previously undetected patterns linked to locomotor behaviour in extant apes and can provide further insight into hip joint loading in fossil hominins and other primates.</jats:p>