June 9, 2015Slide 1 of 21 Unveiling the structural response of the ribcage: Contribution of the intercostal muscles to the thoracic mechanical response David Poulard Center for Applied Biomechanics, University of Virginia USA Damien Subit Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech France

June 9, 2015Slide 2 of 21 Thoracic injuries in motor vehicle crashes = most common blunt trauma

June 9, 2015Slide 3 of 21 Number of Rib fractures (NFR): Indicator of a crash severity Straight forward to detectInternal injuries (↗) Aorta Lungs Heart

June 9, 2015Slide 4 of 21 Human FE models Allow to: – Consider new designs for safety – Interpret experimental results – Investigate response to impact (sensitivity studies) Rely on – Experimental data for evaluation – Material and geometrical information GHBMC Based on PMHS

June 9, 2015Slide 5 of 21 Experimental data for validation Isolated thoracic components Clavicle Ribs Costal cartilage Organs Muscles Skin GHBMC Kemper, 2005 Duprey, 2008 Charpail, 2005 Li, 2010 Guo, 2007 Forman, 2010 Yamada, 1970 Hedenstierna et al Deng, 1999 Yuen, 2009 Yamada, 1970

June 9, 2015Slide 6 of 21 Clavicle Ribs Costal cartilage Organs Muscles Skin GHBMC Kemper, 2005 Duprey, 2008 Charpail, 2005 Li, 2010 Guo, 2007 Forman, 2010 Yamada, 1970 Hedenstierna et al Deng, 1999 Yuen, 2009 Yamada, 1970Intercostal muscles Experimental data for validation Isolated thoracic components

June 9, 2015Slide 7 of 21 Intercostal muscles Response – Few data available – Generate less tensile force than the other muscles – Hyperelastic Modelling – Derived from trapezius and pectoralis material props. – Elastic behavior Role – Define thoracic cavity – Expand and shrink the ribcage for breathing Anatomy – Run between the ribs – Three layers

June 9, 2015Slide 8 of 21 Intercostal muscles Response – Few data available – Generate less tensile force than the other muscles – Hyperelastic Modelling – Derived from trapezius and pectoralis material props. – Elastic Role – Define thoracic cavity – Expand and shrink the ribcage for breathing Anatomy – Run between the ribs – Three layers

June 9, 2015Slide 9 of 21 Intercostal muscles Response – Few data available – Generate less tensile force than the other muscles – Hyperelastic (Hamzah, 2013) Modelling – Derived from trapezius and pectoralis material props. – Elastic Role – Define thoracic cavity – Expand and shrink the ribcage for breathing Anatomy – Run between the ribs – Three layers

June 9, 2015Slide 10 of 21 Hamza et al Experiments Quasi-static

June 9, 2015Slide 11 of 21 Hamza et al Experiments Model (GHBMC V4.1)

June 9, 2015Slide 12 of 21 The contribution of the intercostal muscles is not properly included in FE models due to lack of experimental data… …which could limit their rib fracture prediction capabilities

June 9, 2015Slide 13 of 21 Objective Examine the sensitivity of a FE model to the changes in intercostal muscle material constitutive model based on recent literature GHBMC v4.1

June 9, 2015Slide 14 of 21 GHBMC v4.1 AM50 occupant Geometries from CT, MRI 1.9 million elements

June 9, 2015Slide 15 of 21 Defining new material properties for the intercostal muscles Experiments (n=3) Hamzah et al. (2013)

June 9, 2015Slide 16 of 21 Defining new material properties for the intercostal muscles GHBMC v4.1 (elastic) Linear elastic (E=0.5 Mpa) Experiments (n=3) Hamzah et al. (2013)

June 9, 2015Slide 17 of 21 Defining new material properties for the intercostal muscles Average GHBMC v4.1 (elastic) Linear elastic (E=0.5 Mpa) Experiments (n=3) Hamzah et al. (2013) GHBMC v4.1 (hyperelastic) Simplified rubber foam

June 9, 2015Slide 18 of 21 Evaluation cases Progressive complexity GHBMC v4.1 (elastic) evaluated in Poulard et al., 2015

June 9, 2015Slide 19 of 21 Evaluation cases Progressive complexity

June 9, 2015Slide 20 of 21 Point loading of the ribcage Kindig et al., Scaled Displacement (mm) Lower sternum Scaled Force (N) Scaled Displacement (mm) Upper sternum Scaled Displacement (mm) Rib1_CCJ Scaled Displacement (mm) Rib3_CCJ Scaled Displacement (mm) Rib4_CCJ Scaled Displacement (mm) Rib6_CCJ Scaled Displacement (mm) Rib9_CCJ GHBMC v4.1 (elastic) GHBMC v4.1 (hyperelastic) Experimental corridor (± 1 S.D.) Scaled Force (N) Rib1_CCJ Rib3_CCJ Rib4_CCJ Rib6_CCJ Rib9_CCJ Upper Sternum Lower Sternum More compliant

June 9, 2015Slide 21 of 21 Evaluation cases Progressive complexity More compliant

June 9, 2015Slide 22 of 21 Lateral pendulum impact Shaw et al., Force (N) Deflection (mm) GHBMC v4.1 (elastic) GHBMC v4.1 (hyperelastic) Experimental corridor No change

June 9, 2015Slide 23 of 21 Evaluation cases Progressive complexity More compliant No change

June 9, 2015Slide 24 of 21 Table tops Kent et al., %5%10%15%20% Reaction Force (N) Chest Compression (%) Hub Loading %5%10%15%20% Single Belt %5%10%15%20% Chest Compression (%) Double Belt %5%10%15%20% Distributed Loading Reaction Force (N) Chest Compression (%) GHBMC v4.1 (elastic) GHBMC v4.1 (hyperelastic) Experimental corridor No change

June 9, 2015Slide 25 of 21 Evaluation cases Progressive complexity More compliant No change

June 9, 2015Slide 26 of 21 Frontal pendulum impact Kroell et al., Force (kN) Deflection (mm) GHBMC v4.1 (elastic) GHBMC v4.1 (hyperelastic) Experimental corridor (Lebarbe and Petit 2012) No change

June 9, 2015Slide 27 of 21 Main results after model update Progressive complexity More compliant No change

June 9, 2015Slide 28 of 21 GHBMC v4.3 Objective Examine the sensitivity of a FE model to the changes in intercostal muscle material constitutive model based on recent literature ?

June 9, 2015Slide 29 of 21 Quantification using CORA Magnitude 0≤m≤1 Magnitude 0≤m≤1 Shape 0≤s≤1 Shape 0≤s≤1 Phase p (time units) Phase p (time units) Cross-Correlation Xu 2000 (OSRP), Nusholtz 2007, Gehre 2009 (ISO) Cross-Correlation Xu 2000 (OSRP), Nusholtz 2007, Gehre 2009 (ISO)

June 9, 2015Slide 30 of 21 Quantitative Comparison of Models Response to PMHS Occupant Displacement – Force vs. Time histories – Deflection vs. Time histories ANOVA Analysis: p>0.05 All models are Similar Relative to PMHS

June 9, 2015Slide 31 of 21 Discussion Model response focused on global response – Point loading -> localized effect – Strain distribution in the ribcage? Experimental data – Few samples (n=3) – Quasistatic tests ICM in the model – No fiber orientation – One layer (Three layers) Better CT’s needed Dynamic tests Validation of the strain distribution?

June 9, 2015Slide 32 of 21 Conclusions Constitutive models of the ICM have little effect on the model response (Force vs. Deflection) Localized effect – Except in point loading (Localized effect) Localized effect may be captured by analyzing the strain distribution in the ribcage Experimental data is needed to further investigate the strain distribution in the ribs and how the ICM influence them

June 9, 2015Slide 33 of 21 David Poulard, Ph.D. Research Associate Contact Me Funding/Technical Support: GHBMC