Daniel P. Moreno

An Evaluation of Objective Rating Methods for Full-Body Finite Element Model Comparison to PMHS Tests

Objective: Objective evaluation methods of time history signals are used to quantify how well simulated human body responses match experimental data. As the use of simulations grows in the field of biomechanics, there is a need to establish standard approaches for comparisons. There are 2 aims of this study. The first is to apply 3 objective evaluation methods found in the literature to a set of data from a human body finite element model. The second is to compare the results of each method, examining how they are correlated to each other and the relative strengths and weaknesses of the algorithms. Methods: In this study, the methods proposed by Sprague and Geers (magnitude and phase error, SGM and SGP), Rhule et al. (cumulative standard deviation, CSD), and Gehre et al. (CORrelation and Analysis, or CORA, size, phase, shape, corridor) were compared. A 40 kph frontal sled test presented by Shaw et al. was simulated using the Global Human Body Models Consortium midsized male full-body finite element model (v. 3.5). Mean and standard deviation experimental data (n = 5) from Shaw et al. were used as the benchmark. Simulated data were output from the model at the appropriate anatomical locations for kinematic comparison. Force data were output at the seat belts, seat pan, knee, and foot restraints. Results: Objective comparisons from 53 time history data channels were compared to the experimental results. To compare the different methods, all objective comparison metrics were cross-plotted and linear regressions were calculated. The following ratings were found to be statistically significantly correlated (P < .01): SGM and CORrelation and Analysis (CORA) size, R 2 = 0.73; SGP and CORA shape, R 2 = 0.82; and CSD and CORAs corridor factor, R 2 = 0.59. Relative strengths of the correlated ratings were then investigated. For example, though correlated to CORA size, SGM carries a sign to indicate whether the simulated response is greater than or less than the benchmark signal. A further analysis of the advantages and drawbacks of each method is discussed. Conclusions: The results demonstrate that a single metric is insufficient to provide a complete assessment of how well the simulated results match the experiments. The CORA method provided the most comprehensive evaluation of the signal. Regardless of the method selected, one primary recommendation of this work is that for any comparison, the results should be reported to provide separate assessments of a signals match to experimental variance, magnitude, phase, and shape. Future work planned includes implementing any forthcoming International Organization for Standardization standards for objective evaluations. Supplemental materials are available for this article. Go to the publishers online edition of Traffic Injury Prevention to view the supplemental file.

Validation of Simulated Chestband Data in Frontal and Lateral Loading Using a Human Body Finite Element Model

Objective: Finite element (FE) computer models are an emerging tool to examine the thoracic response of the human body in the simulated environment. In this study, a recently developed human body model, the Global Human Body Models Consortium (GHBMC) mid-sized male, was used to examine chestband contour deformations in a frontal and lateral impact. The objective of this study was 2-fold. First, a methodology for extracting and analyzing virtual chestband data from a full-body FE model is presented. Then, this method is applied to virtual chestband data from 2 simulations to evaluate the models performance against experimental data. Methods: One frontal and one lateral impact case were simulated using the FE model, which was preprogrammed with upper, middle, and lower chestbands. Maximum compression was determined using established techniques. Furthermore, a quadrant-based analysis technique for the results was introduced that enabled regional comparisons between the model and the experimental data in the anterior, posterior, right, and left sections of the chestband. Results: For the frontal case at 13.3 m/s, the model predicted a peak compression of 13.6 and 12.9 percent for the upper and middle chestbands. For the lateral case at 6.7 m/s, the model predicted peak compression of the upper, middle, and lower chestbands of 27.9, 26.0, and 20.4 percent. Regional analysis showed average differences at maximum deformation between the model and experiments ranging from 0.9 percent (posterior) to 6.3 percent (anterior) in the frontal case and 2.3 percent (posterior) to 10.8 percent (anterior) in the lateral case. The greatest difference between model and experimental findings was found in the anterior quadrant. Conclusions: Though this work was focused on techniques to extract and analyze chestband data from FE models, the comparative results provide further validation of the model used in this study. The results suggest the importance of evaluating comparisons between virtual and experimental chestband data on a regional basis. These data also provide the potential to correlate chestband deformations to the loading of underlying thoraco-abdominal structures. Supplemental materials are available for this article. Go to the publishers online edition of Traffic Injury Prevention to view the supplemental file.

Cross-sectional neck response of a total human body FE model during simulated frontal and side automobile impacts

Human body finite element (FE) models are beginning to play a more prevalent role in the advancement of automotive safety. A methodology has been developed to evaluate neck response at multiple levels in a human body FE model during simulated automotive impacts. Three different impact scenarios were simulated: a frontal impact of a belted driver with airbag deployment, a frontal impact of a belted passenger without airbag deployment and an unbelted side impact sled test. Cross sections were created at each vertebral level of the cervical spine to calculate the force and moment contributions of different anatomical components of the neck. Adjacent level axial force ratios varied between 0.74 and 1.11 and adjacent level bending moment ratios between 0.55 and 1.15. The present technique is ideal for comparing neck forces and moments to existing injury threshold values, calculating injury criteria and for better understanding the biomechanical mechanisms of neck injury and load sharing during sub-injurious and injurious loading.

Comparison of Organ Location, Morphology, and Rib Coverage of a Midsized Male in the Supine and Seated Positions

The location and morphology of abdominal organs due to postural changes have implications in the prediction of trauma via computational models. The purpose of this study is to use data from a multimodality image set to devise a method for examining changes in organ location, morphology, and rib coverage from the supine to seated postures. Medical images of a male volunteer (78.6 ± 0.77 kg, 175 cm) in three modalities (Computed Tomography, Magnetic Resonance Imaging (MRI), and Upright MRI) were used. Through image segmentation and registration, an analysis between organs in each posture was conducted. For the organs analyzed (liver, spleen, and kidneys), location was found to vary between postures. Increases in rib coverage from the supine to seated posture were observed for the liver, with a 9.6% increase in a lateral projection and a 4.6% increase in a frontal projection. Rib coverage area was found to increase 11.7% for the spleen. Morphological changes in the organs were also observed. The liver expanded 7.8% cranially and compressed 3.4% and 5.2% in the anterior-posterior and medial-lateral directions, respectively. Similar trends were observed in the spleen and kidneys. These findings indicate that the posture of the subject has implications in computational human body model development.

Investigation of the mass distribution of a detailed seated male finite element model.

Accurate mass distribution in computational human body models is essential for proper kinematic and kinetic simulations. The purpose of this study was to investigate the mass distribution of a 50th percentile male (M50) full body finite element model (FEM) in the seated position. The FEM was partitioned into 10 segments, using segment planes constructed from bony landmarks per the methods described in previous research studies. Body segment masses and centers of gravity (CGs) of the FEM were compared with values found from these studies, which unlike the present work assumed homogeneous body density. Segment masses compared well to literature while CGs showed an average deviation of 6.0% to 7.0% when normalized by regional characteristic lengths. The discrete mass distribution of the FEM appears to affect the mass and CGs of some segments, particularly those with low-density soft tissues. The locations of the segment CGs are provided in local coordinate systems, thus facilitating comparison with other full body FEMs and human surrogates. The model provides insights into the effects of inhomogeneous mass on the location of body segment CGs.

Effects of cervical arthrodesis and arthroplasty on neck response during a simulated frontal automobile collision

BACKGROUND CONTEXT Whereas arthrodesis is the most common surgical intervention for the treatment of symptomatic cervical degenerative disc disease, arthroplasty has become increasingly more popular over the past decade. Although literature exists comparing the effects of anterior cervical discectomy and fusion and cervical total disc replacement (CTDR) on neck kinematics and loading, the vast majority of these studies apply only quasi-static, noninjurious loading conditions to a segment of the cervical spine. PURPOSE The objective of this study was to investigate the effects of arthrodesis and arthroplasty on biomechanical neck response during a simulated frontal automobile collision with air bag deployment. STUDY DESIGN This study used a full-body, 50th percentile seated male finite element (FE) model to evaluate neck response during a dynamic impact event. The cervical spine was modified to simulate either an arthrodesis or arthroplasty procedure at C5-C6. METHODS Five simulations of a belted driver, subjected to a 13.3 m/s ΔV frontal impact with air bag deployment, were run in LS-DYNA with the Global Human Body Models Consortium full-body FE model. The first simulation used the original model, with no modifications to the neck, whereas the remaining four were modified to represent either interbody arthrodesis or arthroplasty of C5-C6. Cross-sectional forces and moments at the C5 and C6 cervical levels of the neck, along with interbody and facet forces between C5 and C6, were reported. RESULTS Adjacent-level, cross-sectional neck loading was maintained in all simulations without exceeding any established injury thresholds. Interbody compression was greatest for the CTDRs, and interbody tension occurred only in the fused and nonmodified spines. Some interbody separation occurred between the superior and inferior components of the CTDRs during flexion-induced tension of the cervical spine, increasing the facet loads. CONCLUSIONS This study evaluated the effects of C5-C6 cervical arthrodesis and arthroplasty on neck response during a simulated frontal automobile impact. Although cervical arthrodesis and arthroplasty at C5-C6 did not appear to significantly alter the adjacent-level, cross-sectional neck responses during a simulated frontal automobile impact, key differences were noted in the interbody and facet loading.

A Multi-Modality Dataset for the Development of a Small Female Full Body Finite Element Model

Motor vehicle fatalities and injuries remain a leading public health problem worldwide. In 2009, the World Health Organization reported more than 1.2 million people die each year worldwide as a result of motor vehicle crash [1]. Researchers are using a wide array of tools to mitigate the societal tool of this epidemic, and finite element (FE) computer models are one method gaining interest in the biomechanics field. Full body FE models are used to examine the potential for occupant injury in vehicle crash. Such models are often built to represent an average (50th percentile) male occupant [2]. However computational models can be made to represent essentially any driving cohort.© 2013 ASME

Application of a Standard Quantitative Comparison Method to Assess a Full Body Finite Element Model in Frontal Impact

Advanced human body finite element models (FEMs) are gaining popularity in the study of injury biomechanics [1, 2]. FEMs must be validated to ensure that model outputs correspond to experimentally-observed phenomena. During the validation process researchers often qualitatively compare the model response to a laboratory experiment. However, a more rigorous approach is to use quantitative methods. Often, these methods attempt to parse the error contributions of phase, magnitude, and a shape factor. The purpose of this study is to apply one such method for validation quantification, called the enhanced error assessment of response time histories (EEARTH), to a model that was recently developed. The EEARTH method is anticipated to be part of the forthcoming ISO standard (ISO/TC 22/SC 10/WG 4) on comparing model outcomes to experimental data. The subject of this study is the Global Human Body Models Consortium (GHBMC) 50th percentile male seated model (M50). The mission statement of the consortium is to develop a set of biofidelic computational human body models to aid in the study injury biomechanics and safety system enhancement.Copyright

Methods for Comparison of Liver and Spleen Location in the Supine and Upright Positions of the 50th Percentile Male

The location and shape variation of the liver and spleen due to postural changes has implications in the prediction of blunt abdominal trauma via computational models or other human surrogates. Although abdominal injuries occur in only 3–5% of injuries in car crashes, they are often seen in serious crashes with AIS≥4 injuries. The location and shape variation of the liver and spleen due to postural changes are likely to play a role in the severity of injury, as a result of rib coverage and location. One means of studying this variation is through computational modeling for impact biomechanics studies. This study reviews the methods used to quantify variation in the location of the liver and the spleen relative to surrounding bony structures for two different postures, supine and seated. Through the use of various imaging modalities three-dimensional datasets depicting the affect of posture change on the size and shape of the liver and spleen can be investigated through three-dimensional renderings and center of gravity measurements.Copyright

The Effect of Impactor Location on the Validation of a Full Body Finite Element Model in Two Loading Cases

Finite element analysis (FEA) is a tool used by many in the injury biomechanics field. FEA allows researchers to study the stresses and strains in complex loading scenarios that would be impossible to determine experimentally. A vital step toward ensuring accurate results is validation of the finite element model (FEM), which is often based on matching model results to experimental results. While care is taken in performing experiments, there are still sources of variance in empirical results like experimental error and cadaver variation. In order to mimic these, location variations of two validation cases were studied, an oblique impact to the right thoracoabdominal region and a lateral impact to the right shoulder. Five locations were studied for each case, the nominal and four variations. The object of this study was to determine model robustness, conduct a sensitivity study of the model, and to simulate experimental subject variation without the use of subject-specific models. This study utilizes the Global Human Body Models Consortium (GHBMC) midsized male model. The model reflects a global effort to develop a set of state-of-the-art full body finite element models.Copyright