engleski

Trabecular properties - loading history of the hallux at toe-off

Unlike African apes, human experience very high loads on their hallux just prior to toe-off at the end of stance phase of locomotion. Because of this difference, trying to determine the habitual loading regime of the hallux in fossil hominins would prove to be a useful endeavour to better characterize the evolution of human locomotor biomechanics. A few studies have successfully shown that cortical bone cross- sectional properties in the hallucal metatarsal differ between apes and humans, with fossil hominins tending to have an intermediate morphology. While these finding are valuable, they do not necessarily reflect the loading history of the hallux at toe-off since it is the distal hallucal phalanx (DHP) that bears the majority of weight (in humans) at this point in the gait cycle. In the current study, we investigated trabecular bone architecture of the DHP in a small sample of humans (n=10), African apes (n=8 each for gorilla and chimpanzee) and fossil hominins. The fossil hominin sample included specimens attributed to Au. africanus, early Homo, and H. erectus. We predicted that modern humans would differ from African apes, and that fossil hominins would have an intermediate morphology between these extant groups. The following properties were calculated: bone volume fraction, trabecular number, trabecular thickness, trabecular separation and degree of anisotropy. Estimated body mass was used for scaling purposes. Our preliminary results demonstrate that humans are different from African apes in most trabecular properties. But, the principal orientation of trabecular bone struts between groups run in a similar direction - The Homo erectus specimen is most similar to modern humans, while the other hominin DHPs show different patterns. However, neither of these are ape-like. These findings allow us to discuss possible scenarios of the evolution of human locomotor biomechanics, especially the toe-off mechanism specialized in humans.

hallux; trabecular bone architecture; African apes; fossil hominins; locomotor biomechanics

nije evidentirano