1Department of Paleoanthropology and Messel Research, Senckenberg Research Institute Frankfurt, 2Département de Préhistoire, UMR 7194, MNHN Paris,, 3Société Etudes Recherches Matériaux, Poitiers, 4Département Géosciences, Université de Poitiers
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Relative to extant humans, the Neanderthal lower limb skeleton exhibits greater diaphyseal robusticity, which is consistent with a higher level of mechanical loads experienced throughout life. The adult tibial diaphysis is reported to have thickened cortical bone and greater strength in the medio-lateral plane. At the knee joint, the distribution of the cortico-trabecular complex (CTC) beneath the tibial plateau indicates bone reinforcement at both condyles compared to the modern condition.
As the structural organization and textural properties of the cancellous bone provide direct information about the nature, direction, and magnitude of the habitual loads, we have assessed the still unreported pattern characterizing the trabecular network underlying the Neanderthal tibial plateau in the right specimen La Ferrassie 2 (France).
By using a synchrotron radiation microtomographic record realised at the ESRF medical beamline ID17 of Grenoble (45.5×45.5×43.6 µm voxel size), we have quantified the parameters of bone volume fraction, degree of anisotropy, and trabecular thickness topographic variation in a selected number of regions (ROI) and volumes (VOI) of interest under the CTC of each condyle.
Immediately below the cortical shell and along the coronal plane, this young adult Neanderthal plateau shows a layer composed of relatively and absolutely thick trabeculae, significantly thicker than those measured at homologous sites in the modern human sample available to us. This transitional layer overlaps a more finely structured/oriented trabecular network.
Our analysis shows that the medial condyle records a preferential strengthening of the cancellous pattern expressed by a greater density and degree of anisotropy.