Biomechanics of the Neck in Rear Impacts for improved Seat Design

Biomechanics of the Neck in Rear Impacts for improved Seat Design Dr.-Ing. Tjark Kreuzinger Regulatory & Technical Affairs Toyota Motor Europe NV/SA Studiedag BEPALING VAN MENSELIJKE SCHADE DOOR SLINGERLETSELS VAN DE NEK 27.11.2010, Leuven

Agenda 1. Background 2. WHIPLASH Symptoms vs. Injuries 3. Injury vs. Injury Criteria 4. Human Model THUMS 5. Designing Headrest with THUMS

Agenda 1. Background 2. WHIPLASH Symptoms vs. Injuries 3. Injury vs. Injury Criteria 4. Human Model THUMS 5. Improved Headrest Design with THUMS

1. Background Development towards Real-World Safety 9. Effectiveness Analysis in the Field 1. Traffic Accident Analysis (Macro Data) Society Stage Today s Talk 2. Traffic Accident Analysis (Micro Data) Traffic Stage Driver Stage 3. Driver Behavior Analysis 4.System Concept System Stage 5. System Requirements 8. Effectiveness Estimation 7. System Test 6. Function Test

1. Background From Injury to Injury Criteria for Whiplash Injury Symptom Injury Mechanism For Whiplash Sensor Threshold (estimated) Injury Criteria

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Symptoms: Neck pain, headache, vision disorder, dizziness, unconsciousness, neurological symptoms and other Dummy Requirements and Injury Criteria for a Low-speed Rear Impact Whiplash Dummy. EEVC WG12 report, p.29, September 2007 Schmitt, K.U. Trauma Biomechanics, 2 nd Edition, p.91

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Physiological damage (injured body region): Yoganandan et al. (2000) reported injuries to several ligaments, the intervertebral discs and the facet joint structures. Taylor et al. (1998) and Svensson et al. (2000) reported damage in cervical spinal root ganglia Brault et al. (2000) reported muscle injuries Dummy Requirements and Injury Criteria for a Low-speed Rear Impact Whiplash Dummy. EEVC WG12 report, p.29, September 2007 But muscle stiffness following the impact typically last only a few days Whiplash associated disorders: a comprehensive review, p. 31. Anderson et al. Centre for Automotive Safety Research. University of Adelaide. April 2006.

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Injury mechanism: Hyperextension of the neck not relevant any more Muscle strains unlikely and pain only last for a few days Spinal column pressure pulses could cause ganglion damage Cervical spine motion - has been shown to be able to lead to facet joint impingement Neck shear force can cause excessive facet joint strain. Neck compression can cause the facet capsules to stretch and possibly torn, resulting in inflammation and pain. Whiplash associated disorders: a comprehensive review, p. 36-38. Anderson et al. Centre for Automotive Safety Research. University of Adelaide. April 2006.

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Several injury criteria (response measurement) Item Who? Year Where? Associated injury mechanism '96 IRCOBI NIC Bostrom - Pressure pulses in spinal ganglia Nkm Schmitt '01 ESV - Excessive load (some relation with facet injury) Heitplatz LNL '03 ESV - Excessive load (some relation with facet injury) Kullgren MIX '03 ESV - (combination of NIC and Nkm) WIC Muñoz '05 ESV - (excessive load?)

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Several injury criteria (kinematic measurement) Item Who? Year Where? Associated injury mechanism IV-NIC Panjabi '99 IRCOBI - Facet joint (excessive IV rotation) VT1 Muser '00 IRCOBI - (excessive load in rebound phase) NDC Viano '02 SAE PWI Mallory '05 ESV Head RV T-HRC - (Kinematic measurement for excessive load) - (Head rotation) - (excessive load in rebound phase) - (Head to headrest contact timing)

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review None of the proposed injury criteria were found to have a definite biomechanical basis and their validity in predicting the risk needs to be established. None of the criteria can be recommended on a strictly biomechanical basis. Dummy Requirements and Injury Criteria for a Low-speed Rear Impact Whiplash Dummy. EEVC WG12 report, p.29, September 2007 However, some valuable insight can be gained from a biomechanical review of Whiplash injuries.

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Half of Whiplash injuries are cervical joint injury, Barnsley 1995, Manchikanti 2004 Shear and compression at cervical joint capsule causes injury, Yang and Begeman 1996 Largest angle displacement is found between C5 and C6 in Voluntary test, Ono 1997, Stemper 2007 Largest strain is found at joint capsule between C5 and C6 in cadaver test, Deng 2000, Pearson 2004 Peak angle displacement between C5 and C6 in voluntary test, Ono

2. WHIPLASH Symptoms vs. Injuries Biomechanics of Whiplash injuries Injury criteria review Physiological damage (injured body region) The structures most likely to be injured in whiplash are the facet capsule, the intervertebral discs and the upper cervical ligaments. Injuries to other structures may occur but the available evidence appears to suggest that these are less common Whiplash associated disorders: a comprehensive review, p. 31. Anderson et al. Centre for Automotive Safety Research. University of Adelaide. April 2006. Conclusion: Need to measure Human Threshold

Seat Concepts vs. Injury Risk & Rating THATCHAM Rating Number Risk Risk reduction Make/Model Year Rating report 1 month permanent 1 month permanent 1 month permanent Avensis 2003-2009 A 63 5 1 7.9% 1.6% 39.3% 82.4% Corolla 2002-2006 P 104 17 5 16.3% 4.8% -25.1% 46.8% Corolla Verso 2004-2009 P 21 2 1 9.5% 4.8% 27.1% 47.3% Prius 2004-2009 M 14 0 0 0.0% 0.0% 100.0% 100.0% Rav4 2000-2005 M 50 4 1 8.0% 2.0% 38.8% 77.9% WIL (l&ll) 1998- > 399 46 16 11.5% 4.0% 11.8% 55.6% SAHR 1998- > 171 13 6 7.6% 3.5% 41.8% 61.2% WHIPS 1998- > 126 12 5 9.5% 4.0% 27.1% 56.1% All others w. RHR 1998- > 116 16 7 13.8% 6.0% -5.6% 33.2% Std.from 98 1998- > 2269 333 179 14.7% 7.9% -12.3% 12.7% All before 98 -> 1998 7241 946 654 13.1% 9.0% 0.0% 0.0% 16.0% 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% Injury Risk 1 month permanent WIL (l&ll) SAHR WHIPS All others w. RHR Std.from 98 All before 98 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% Injury Risk Reduction 1 month permanent WIL (l&ll) SAHR WHIPS All others w. RHR Std.from 98 All before 98 FOLKSAM Insurance data, 2009

3. Injury vs. Injury Criteria IIWPG Rating & Relative LT Risk W/O, Cars after 97 With Anti_whiplash Whiplash System W/O, Cars before 97 0.16 0.146 0.14 Relative LT Risk (%) 0.12 0.1 0.08 0.06 0.04 0.02 0.064 Slight differences 0.071 0.07 0.092 0 Good Acceptable Marginal Poor Not tested Bostrom, Kullgren (IRCOBI 2007)

4. Human Model THUMS THUMS Total Human Model for Safety Jointly developed with Toyota Central R&D Labs., Inc. Skull Shoulder blade Collarbone Brain Upper arm bone Lung Liver Heart Stomach Intestines Knee Foot (Pictures can show different versions)

THUMS development THUMS is jointly developed by Toyota Motor Corporation and Toyota Central R&D Labs It represents an average size adult male of 175 cm height and 77 kg weight (Other size or gender models are developed if necessary) Version 1, finalised in 2000, was aiming to simulate major bones and ligaments Version 2, finalised in 2004, enhanced facial bone fracture simulation Version 3, finalised in 2008, introduced an enhanced brain model Version 4, finalised in 2009, is able to simulate internal organ injuries

Pedestrian Impact with THUMS

Tibia Bone fracture of Pedestrian

5. Improved Headrest Design with THUMS THUMS neck structure Detailed Model facet joint capsular Cervical vertebrae THUMS Human

5. Improved Headrest Design with THUMS THUMS simulation of Rear Impact - WIL

5. Improved Headrest Design with THUMS THUMS simulation of Rear Impact - WIL ll

5. Improved Headrest Design with THUMS Mechanism of cervical facet joint capsular strain H/R contact Max H/R reaction force Max Joint capsule strain H/R separate Max S/B force 0ms 66ms 100ms 148ms Rotation of upper cervical vertebra Rotation and translation of upper cervical vertebra Translation of lower cervical vertebra Tension force Tension and shear force Shear force Conclusion: The peak strain happens during end of head contact

5. Improved Headrest Design with THUMS Headrest Design with THUMS WIL WIL ll Active WIL Vertebral injury index (including ligaments) WIL=1 WIL WIL ll Active WIL

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