Abstract
As human body finite element models become more integrated with the design of safety countermeasures and regulations, novel models need to be developed that reflect the variation in the population's anthropometry. However, these new models may be missing information which will need to be translated from existing models. During the development of a 5th percentile female occupant model (F05), cortical thickness information of the coxal bone was unavailable due to resolution limits in the computed tomography (CT) scans. In this study, a method for transferring cortical thickness information from a source to a target model with entirely different geometry and architecture is presented. The source and target models were the Global Human Body Models Consortium (GHBMC) 50th percentile male (M50) and F05 coxal bones, respectively. To project the coxal bone cortical thickness from the M50 to the F05, the M50 model was first morphed using a Kriging method with 132 optimized control points to the F05 anthropometry. This technique was found to be accurate with a mean nodal discrepancy of 1.27 mm between the F05 and morphed M50 (mM50) coxal bones. Cortical thickness at each F05 node was determined by taking the average cortical thickness of every mM50 node, non-linearly weighted by its distance to the F05 nodes. The non-linear weighting coefficient, β, had a large effect on the accuracy and smoothness of the projected cortical bone thickness. The optimal projection had β = 4 and was defined when the tradeoff between projection accuracy and smoothness was equal. Finally, a quasi-static pelvis compression was simulated to examine to effect of β. As β, increased from 0 to 4, the failure force decreased by ~100 N, whereas the failure displacement increased by 0.9 mm. Results from quasi-static compression tests of the F05 pelvis were comparable to experimental results. This method could be applied to other anatomical regions where cortical thickness variation is important, such as the femur and ribs and is not limited to GHBMC-family models. Furthermore, this process will aid the development of subject-specific finite element models where accurate cortical bone thickness measurements cannot be obtained.
Highlights
Pelvic fracture is a significant cause of disability and mortality (Gokcen et al, 1994; Inaba et al, 2004)
Finite element analysis (FEA) is widely used in the automotive injury for assessing human body models (HBM) in injurious loading conditions, such as pedestrian and automotive impacts (Nie et al, 2017, 2018; Wu et al, 2017; Chen et al, 2018)
The ability to predict pelvic fracture using FEA is largely contingent on an accurate representation of the cortical layer of the coxal bone, which has been shown to vary regionally throughout its structure (Besnault et al, 1998; Anderson et al, 2008; Kim et al, 2009; Salo et al, 2012; Ma et al, 2015)
Summary
Pelvic fracture is a significant cause of disability and mortality (Gokcen et al, 1994; Inaba et al, 2004). FEA is widely used in the automotive injury for assessing human body models (HBM) in injurious loading conditions, such as pedestrian and automotive impacts (Nie et al, 2017, 2018; Wu et al, 2017; Chen et al, 2018) These models have a large role as they have a profound impact on the development of new countermeasures and government safety regulations. Anderson et al demonstrated that by increasing the radiation dosage beyond clinically safe levels, the coxal bone cortical thickness measurements of a cadaveric specimen could be made with less than 10% error (Anderson et al, 2005) This method was limited to cadaveric pelves as radiation doses are strictly regulated in the clinical setting and is only practical for subject specific models where cadaveric CT images are used for both thickness calculations and to define the FE model geometry
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