Tag Archives: skull

FEA, Validity & Sensitivity

fea-validity-smlThe Finite Element Method (FEM) was developed within the framework of Engineering but has become a popular tool in bio-mechanical studies. It is natural that computational bio-mechanics and Finite Element Analysis (FEA) became increasingly promising in fossil studies where there are no examples of some taxa still living. To study the bio-mechanical responses of fossil hominids, modern humans and non-human primates are often used as comparative samples for which there are already known values. Despite this, precisely how accurately computational bio-mechanics compares with physical studies is still not well understood. The biological composition of bone and dentition is hard to replicate in computational terms with the cranium a mixture of trabecular and cortical bone while teeth comprise variable layers of enamel and dentine. The resolution required from Computed Tomography (CT) scans to accurately capture these finer biological compositions is not feasible for the heavy demands on software to analyze such FEA models with flow-effects for the number of specimens that can be included into any single study.

Godinho et al investigated the validity and sensitivity of Finite Element (FE) models using a direct comparison with a human cadaver. Results were particularly affected if the model was simplified by assigning all materials as cortical bone, including dentition and trabecular bone components. Results showed that the real and virtual skull showed no differences in strain magnitude; differences in strain pattern (high or low strain distribution) were only partially different; simplifying the virtual model decreased the strain magnitude; simplifying the virtual model partially affected the strain pattern with the regions near the dentition, particularly the alveolar ridge, most affected.

For bio-mechanical studies, by not simplifying virtual models and attempting to designate dental and bone tissues properly acknowledges the underpinning biology of the cranium while potentially revealing sensitive adaptations of this biological structure. By adopting these changes, new variations between living and fossil humans, that have so-far been obscured by less time-consuming computational methods, could reveal unique adaptational trends that have real significance for human evolution.

Alannah Pearson


Burning skulls

ight-Gizeh-Rangel-de-LázaroTransluminescence (also called “transillumination“) has been used in medicine as a complement to radiography and other imaging techniques. Basically, it uses a beam of visible light to analyse the opacity patterns of solid object, associated with its thickness or composition. It was used in early craniological studies, and it is practical when you can’t rely on computed tomography. Putting a light behind an object, thinner or less dense areas will transmit more light than thicker or denser parts. We have tried to evaluate the actual efficiency of this methods designing a basic equipment for trans-luminescence, and appling this technique to a sample of robust modern humans sample. The equipment was made with two LED bulbs located on a 1.5 x 2.0 cm PCB (printed circuit board). The pieces were connected to a flexible aluminium arm, joined to a support of the same material which also contained the battery power source. The high luminescence LEDs requires thermal management, so it was necessary to attach an external ventilation system to the PCB bottom. The luminous flux was provided by two Cool-White LEDs, of 1500 lumens each, according to their data sheet specifications. The predominant wavelengths were 450 nm and 600 nm, with a minimum peak at 490 nm and the CCT (correlated color temperature) was in the range of 5000-8300 K. The equipment was introduced into ten skulls, males and females of a modern European population. Although they belong to a recent population, the skulls were robust and heavy, suggesting thick walls and dense bones. In most individuals only the vertex, pterion, and lower part of the temporal squama display a visible and patent light signal. In some cases part of the imprints of the middle meningeal vessels were visible. Generally, it seems that this approach is not much informative, at least with skulls presenting a robust morphology.

Gizéh Rangel de Lázaro