Sabine Compigne

Geometrical personalisation of human FE model using palpable markers on volunteers

It is well established that the tolerance of the human thorax under dynamic loading decreases as age increases (Foret- Bruno et al. 1998; Kent et al. 2003; Lafont and Laumon 2003). This trend may be linked to several concomitant changes in the properties of biological tissues (Zhou et al. 1996), costo-vertebral, costo-chondral joint stiffnesses and joint limits, but also to different thorax morphotypes (Gayzik et al. 2008; Vezin and Berthet November 2009). This study aims at quantifying the influence of main geometrical parameters on thorax mechanical response. To achieve this goal, finite element (FE) simulations using the total human model for safety (THUMS) are carried out by modifying only THUMS anthropometry and thorax geometry while keeping constant the other factors. Anthropometric measurements taken on volunteers of various age, gender and anthropometry were used to perform THUMS geometrical personalisation. In addition, the volunteers were submitted to a low deceleration pulse (Poulard et al. 2011) duringwhich their thoracic response under belt load was measured and which served as validation of the personalised THUMS model.

In-vivo analysis of thoracic mechanical response under belt loading: The role of body mass index in thorax stiffness

Thoracic injuries are a major cause of mortality in frontal collisions, especially for elderly and obese people. Car occupant individual characteristics like BMI are known to influence human vulnerability in crashes. In the present study, thoracic mechanical response of volunteers quantified by optical method was linked to individual characteristics. 13 relaxed volunteers of different anthropometries, genders and age were submitted to non-injurious sled tests (4 g, 8 km/h) with a sled buck representing the environment of a front passenger restrained by a 3-point belt. A resulting shoulder belt force was computed using the external and internal shoulder belt loads and considering shoulder belt geometry. The mid sternal deflection was calculated as the distance variation between markers placed at mid-sternum and the 7th vertebra spinous process of the subject. Force-deflection curves were constructed using resulting shoulder belt force and midsternal deflection. Average maximum chest compression was 7.9±2.3% and no significant difference was observed between overweight subjects (BMI≥25 kg/m²) and normal subject (BMI<25 kg/m²). The overweight subjects exhibited significantly greater resultant belt forces than normal subjects (715±132 N vs. 527±111 N, p<0.05), higher effective stiffness (30.9±10.6N/mm vs. 19.6±8.9 N/mm, p<0.05) and lower dynamic stiffness (42.7±8.71 N/mm vs. 61.7±15.5 N/mm, p<0.05).