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Biomechanics of the Neck in Rear Impacts for improved Seat Design

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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

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1. Background

2. “WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

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1. Background

2. ”WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

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Society Stage 4.System Concept 4.System Concept (Macro Data) (Macro Data) System Stage 7. System Test 7. System Test in the Field in the Field

3. Driver Behavior Analysis

3. Driver Behavior Analysis

Traffic Stage Driver Stage 8. Effectiveness 8. Effectiveness Estimation Estimation 6. Function Test 6. Function Test

2. Traffic Accident Analysis

2. Traffic Accident Analysis

(Micro Data)

(Micro Data)

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Injury

Injury Mechanism

Sensor

Injury Criteria

Threshold

Symptom

(estimated)

For Whiplash

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1. Background

2. ”WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

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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

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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.

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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.

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Several injury criteria (response measurement)

Item Who? Year Where? Associated injury mechanism '96 IRCOBI

NIC Bostrom - Pressure pulses in spinal ganglia

- Excessive load (some relation with facet injury) Schmitt

Nkm '01 ESV

Heitplatz

LNL '03 ESV - Excessive load (some relation with facet injury) Kullgren

MIX '03 ESV - (combination of NIC and Nkm) Muñoz - (excessive load?)

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Several injury criteria (kinematic measurement)

Item Who? Year Where? Associated injury mechanism

Panjabi - Facet joint (excessive IV rotation) IV-NIC '99 IRCOBI

VT1 Muser '00 IRCOBI - (excessive load in rebound phase)

- (Kinematic measurement for excessive load) NDC Viano '02 SAE

- (Head rotation) PWI Mallory '05 ESV

Head RV - (excessive load in rebound phase) T-HRC - (Head to headrest contact timing)

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”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.

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• 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

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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.

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1. Background

2. ”WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

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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% 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% 16.0% 1 month permanent WIL (l&ll) SAHR WHIPS All others w. RHR Std.from 98 All before 98 -20.0% -10.0% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 1 month permanent WIL (l&ll) SAHR WHIPS All others w. RHR Std.from 98 All before 98

Injury Risk Reduction Injury Risk

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0.064 0.071 0.07 0.092 0.146 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

W/O, Cars after 97 With Anti_whiplash System W/O, Cars before 97

With Anti Whiplash System

Slight differences

Relative LT

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1. Background

2. ”WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

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Collarbone Upper arm bone Shoulder blade Brain Skull Knee Foot Heart Stomach Intestines Liver Lung

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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

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1. Background

2. ”WHIPLASH” Symptoms vs. Injuries

3. Injury vs. Injury Criteria

4. Human Model THUMS

(24)

facet joint capsular Cervical vertebrae Human THUMS

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0ms 66ms 100ms 148ms Max S/B force Joint capsule strain Translation of lower cervical vertebra Rotation of upper cervical vertebra

Rotation and translation of upper cervical vertebra

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Vertebral injury index (including ligaments)

Vertebral injury index (including ligaments)

W I L=1

WIL WIL ll Active WIL

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References

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