RESUMEN
Late Miocene fossils from the Lukeino Formation in Kenya's Tugen Hills are assigned to Orrorin tugenensis. Of 20 fossils recovered there to date, 3 are proximal femurs. One of these, BAR 1002'00, preserves an intact head connected to the proximal shaft by an elongated neck. Although this fossil is comparable in size to Pan troglodytes, computerized tomography scans of the neck-shaft junction of BAR 1002'00 reveal that the cortex is markedly thinner superiorly than inferiorly, differing from the approximately equal cortical thicknesses observed in extant African apes, approaching the condition in later hominids, and indicating that O. tugenensis was bipedal.
Asunto(s)
Fémur/anatomía & histología , Fósiles , Hominidae/anatomía & histología , Animales , Fenómenos Biomecánicos , Fémur/diagnóstico por imagen , Cuello Femoral/anatomía & histología , Hominidae/fisiología , Humanos , Kenia , Locomoción , Modelos Anatómicos , Músculo Esquelético/anatomía & histología , Filogenia , Postura , Tomografía Computarizada por Rayos XRESUMEN
A finite element model of a semiconstrained ankle implant with the tibia and fibula was constructed so that the stresses in the polyethylene liner could be computed. Two different widths of talar components were studied and proximal boundary conditions were computed from an inverse process providing a load of five times body weight appropriately distributed across the osseous structures. von Mises stresses indicated small regions of localized yielding and contact stresses that were similar to those in acetabular cup liners. A wider talar component with 36% more surface area reduced contact stress and von Mises stresses at the center of the polyethylene component by 17%.