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Morphological variations of the femoral head-neck junction in historical skeletal material
Background Poirier’s facet, Allen’s fossa and femoral plague are the main morphological variations of the femoral head-neck junction. The study aimed to answer questions about the association between the shape of the proximal end of the femoral bone and acetabulum in bones with head-neck junction changes and the differences in shape and size between joints with the above changes and joints without ones. Methods The analyses were performed on the computed tomography scans (CTs) of the 52 sets of bones (femur and pelvic bone) from the Polish skeletal material dated to the 14th–19th centuries. Based on CTs, three-dimensional models of the femurs and pelvic bones were created and then analysed using linear measurements and a geometric morphometric approach. Analysis of variance (ANOVA) was calculated to analyse differences in size; in turn, canonical variate analysis (CVA) was calculated to investigate changes in shape between bones with femoral-neck changes and bones without ones. Results According to the CVA, there were no significant differences in shape between bones with Allen’s fossa, femoral plaque, or Porier’s facet and hip joints without any observable changes (p > 0.05). Bones with observable Allen’s fossa, femoral plaque, Porier’s facet and hip joints without changes showed similar variations in femoral head shape. The difference was in the femoral head height between bones femoral plaque and bones with Allen’s fossa (p = 0.047, mean difference = 3.78 mm). Acetabula in the sets of bones without head-neck junction changes showed slightly lower shape variation than acetabulum in the sets of bones with changes. In joints with head-neck junction changes, a more indented antero-posterior part of the lunate surface and indented inferior edge along its entire length were observed. Conclusions Geometric morphometrics and measurements showed similarities in the shape of the joints with and without changes in head-neck junction region. This may indicate that morphological changes in the femoral head-neck junction do not significantly affect the morphology of the femur and acetabulum. However, understanding the role and efficiency of this influence needs further studies.
Brain vs. endocast: Does size differ? A unique experiment based on a cohort of 75 volunteers
AbstractResearch on brain evolution centres mainly on internal mouldings of the skull, known as endocasts; however, the relationship between the size and asymmetry of the brain and endocasts has been poorly investigated in humans. Therefore, the main objective of this study was to investigate whether endocasts can be reliable indicators of brain size and asymmetry. Magnetic Resonance Imaging (MRI) of 75 participants was used to calculate the volume and surface area of the brain, the endocast, and their respective hemispheres. Two asymmetry indices (i.e. directional and absolute asymmetry) were used to assess the differences in volume and surface area between the sides of the brain and endocast. The Pearson correlation coefficient was calculated to assess the relationships between the parameters, and a Monte Carlo simulation for linear regression was performed to generate prediction equations for brain volume. The relationships between the level and direction of asymmetry indices were investigated using the Pearson correlation and McNemar's test, respectively. All correlations were statistically significant; however, correlation coefficients between volumes were stronger (0.894–0.931) than between volumes and surface areas (0.783–0.834). Brain volume can be predicted with high accuracy (ranging between 0.80 and 0.87) using the endocast total volume or the volume of one of the sides. The associations between the levels of asymmetry indices of the brain and endocast were non‐significant; however, the McNemar's test indicated that endocasts show the same left‐ or right‐biased asymmetry as the brain. This was the first study conducted on a large sample of brain and endocast data from the same individuals. The results demonstrated that brain volume can be accurately reconstructed using the volume of the endocast or one of its sides. This finding is especially important in the context of reconstructing fossil skulls, which are usually fragmented. Conversely, the asymmetry levels of endocast parameters are not reliable indicators of the actual level of brain volume asymmetry. Future research on fossils should focus on endocast asymmetry direction (left‐ or right‐biased) as this closely corresponds with brain lateralisation.