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					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




TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. “WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Designing Headrest with THUMS



TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. ”WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Improved Headrest Design with THUMS



TOYOTA MOTOR EUROPE
1. Background

 Development towards Real-World Safety
  1. Traffic Accident Analysis                                       9. Effectiveness Analysis
          (Macro Data)                                                  in the Field
                                       Society Stage

                                  Today’s Talk                       8. Effectiveness
   2. Traffic Accident Analysis
                                                                     Estimation
            (Micro Data)                 Traffic Stage




      3. Driver Behavior Analysis        Driver Stage             7. System Test



                                           System
                                            Stage            6. Function Test
                4.System Concept


                                    5. System Requirements

TOYOTA MOTOR EUROPE
1. Background

 From Injury to Injury Criteria for Whiplash


                            Injury              Symptom


                      Injury Mechanism             For Whiplash


                           Sensor         Threshold (estimated)


                        Injury Criteria



TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. ”WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Improved Headrest Design with THUMS



TOYOTA MOTOR EUROPE
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, 2nd Edition, p.91




TOYOTA MOTOR EUROPE
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.




TOYOTA MOTOR EUROPE
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.



TOYOTA MOTOR EUROPE
2. ”WHIPLASH” Symptoms vs. Injuries

 Biomechanics of Whiplash injuries –
 Injury criteria review
  Several injury criteria (response measurement)


  Item    Who?        Year Where? Associated injury mechanism

   NIC Bostrom         '96   IRCOBI - Pressure pulses in spinal ganglia

  Nkm Schmitt          '01     ESV       - Excessive load (some relation with facet injury)

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

   MIX Kullgren        '03     ESV       - (combination of NIC and Nkm)

   WIC     Muñoz       '05     ESV       - (excessive load?)



TOYOTA MOTOR EUROPE
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        - (Kinematic measurement for excessive load)

  PWI      Mallory '05          ESV        - (Head rotation)

  Head RV                                  - (excessive load in rebound phase)

  T-HRC                                    - (Head to headrest contact timing)



TOYOTA MOTOR EUROPE
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.




TOYOTA MOTOR EUROPE
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

TOYOTA MOTOR EUROPE
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


TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. ”WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Improved Headrest Design with THUMS



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




      FOLKSAM Insurance data, 2009

TOYOTA MOTOR EUROPE
3. Injury vs. Injury Criteria

   IIWPG Rating & Relative LT Risk
                                                 W/O, Cars after 97                    Anti_whiplash System
                                                                                  With Anti Whiplash System
                                                 W/O, Cars before 97
                        0.16
                                                                                                        0.146
                        0.14
 Relative LT Risk (%)




                        0.12

                         0.1                 Slight differences                        0.092

                        0.08                           0.071            0.07
                                     0.064
                        0.06

                        0.04

                        0.02

                          0
                                     Good            Acceptable        Marginal         Poor          Not tested
                               Bostrom, Kullgren (IRCOBI 2007)

TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. ”WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Improved Headrest Design with THUMS



TOYOTA MOTOR EUROPE
4. Human Model THUMS

 THUMS – Total Human Model for Safety
 Jointly developed with Toyota Central R&D Labs., Inc.



                                                         Shoulder   Collarbone
                                   Skull                  blade


          Brain                                                        Upper
                                                                        arm
                                                                        bone



                                                                      Knee
                                Heart
        Lung                   Stomach
            Liver
                              Intestines                               Foot



(Pictures can show different versions)

TOYOTA MOTOR EUROPE
 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


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 Pedestrian Impact with THUMS




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 Tibia Bone fracture of Pedestrian




TOYOTA MOTOR EUROPE
 Agenda

  1. Background

  2. ”WHIPLASH” Symptoms vs. Injuries

  3. Injury vs. Injury Criteria

  4. Human Model THUMS

  5. Improved Headrest Design with THUMS



TOYOTA MOTOR EUROPE
5. Improved Headrest Design with THUMS

 THUMS neck structure – Detailed Model



                                         facet joint
                                          capsular

                                           Cervical
                                           vertebrae




                      THUMS                            Human



TOYOTA MOTOR EUROPE
5. Improved Headrest Design with THUMS

 THUMS simulation of Rear Impact - WIL




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5. Improved Headrest Design with THUMS

 THUMS simulation of Rear Impact - WIL ll




TOYOTA MOTOR EUROPE
5. Improved Headrest Design with THUMS

 Mechanism of cervical facet joint capsular strain
                                           H/R contact       Max H/R reaction force    Max              H/R separate
                                                                                       Joint
                                                                                       capsule
                                                                                       strain



                                                 Max
                                             S/B force
             0ms                          66ms                        100ms                     148ms
                                            Rotation and translation of       Translation of lower
    Rotation of upper cervical vertebra     upper cervical vertebra           cervical vertebra




             Tension force                  Tension and shear force                   Shear force

 Conclusion: The peak strain happens during end of head contact

TOYOTA MOTOR EUROPE
5. Improved Headrest Design with THUMS

 Headrest Design with THUMS



                WIL                      WIL ll                   Active WIL

                      Vertebral injury index (including ligaments)
                 W I L=1




                             WIL          WIL ll     Active WIL




TOYOTA MOTOR EUROPE
Thank you




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