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JK_Thorax injury biomechanics

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					                                                                         Janusz Kajzer - Kabimec Consulting                                                                    Janusz Kajzer - Kabimec Consulting




International Course on Transportation Planning and Road
                                                                                                                                               Epidemiology - 1
                          Safety




                    Chest Tolerance and Standards


              Basic anatomy, injury mechanisms
       Biomechanical response, injury criteria & tolerances


                                  New Delhi, 4-11 December, 2009
                                                                                                               Harms 1987, 11:th ESV
                                                                                                                                            Restrained front occupants in frontal collision




                                                                         Janusz Kajzer - Kabimec Consulting                                                                    Janusz Kajzer - Kabimec Consulting


                                                                                                                                         Thorax intercostal wall
                                                     Epidemiology
                                  Incidence of Injury to Each Torso Part




                                                                                                              from: Netter “Atlas CD”




                                                                         Janusz Kajzer - Kabimec Consulting                                                                    Janusz Kajzer - Kabimec Consulting



                                      Thorax: Basic anatomy                                                                                      Thoracic aorta

                                                            General subdivision of thoracic cavity




                     Chest cage

                                                                                                                                        1-Ascending aorta, 2-Aortic arch, 3-Descending aorta

from: Huelke D.F. "The anatomy of the human chest"




                                                                                                        Sidan 1
                                                   Janusz Kajzer - Kabimec Consulting                                                                                Janusz Kajzer - Kabimec Consulting



                          Thorax: Basic anatomy (cont’d)                                                                               Respiration - air flow




                                                                                                                                  Inspiration                    Expiration

                                                                                        from: Huelke D.F. "The anatomy of the human chest"




                                                   Janusz Kajzer - Kabimec Consulting                                                                                Janusz Kajzer - Kabimec Consulting

                                Respiration - muscles
                                                                                                                                     Injury mechanisms

                                                                                                                            • Compression of the thorax -> rib fractures, lung
                                                                                                                                 injuries
                                                                                                                                   – Single rib fractures -> AIS 1 or 2
                                                                                                                                   – 2 - 3 rib fracture -> AIS 2 or 3
                                                                                                                                   – rib multiple fractures may lead to life threatening
                                                                                                                                      complications -> flail chest
                                                                                                                                   – lung injuries
                                                                                                                                        » pneumothorax
                                                                                                                                        » hemothorax
                                                                                                                                        » lung contusion + flail chest -> pneumonia -> ††
                                                                                                                            • shock waves (viscous loading within the
                                                                                                                              thorax cavity) -> lung injuries
                                                                                                                            • inertia loading -> rupture of aorta
from: Netter “Atlas CD”




                                                   Janusz Kajzer - Kabimec Consulting                                                                                Janusz Kajzer - Kabimec Consulting




                           Common thoracic injuries                                                                                          Rib fractures

             Rib fractures are most common
               - Fractures were observed in 93.5% of severely
                 injured belted drives
             Other injuries are:
               - Sternal fractures
               - Liver lacerations
               - Clavicular fracture
                                                                                          - Belt restraints produce fractures along a path near regions of
               - Separation of the sternoclavicular joint
                                                                                            loading under the belt (distribution around rib 6)
                                                                                          - Airbag restraints without belts produce fractures at
                                                                                            anterolateral rib locations                        Kent et al. STAPP 2001




                                                                                  Sidan 2
                                                                Janusz Kajzer - Kabimec Consulting                                               Janusz Kajzer - Kabimec Consulting



                                 Lung injuries – haemo- or
                                                                                                             Injuries to heart and arteries - 1
                                     pneumo-thorax




               Lung collapse and mediastinal shift due to haemo or pneumo -thorax

                                                                                                                        Upward motion of heart
from: Huelke D.F. "The anatomy of the human chest"




                                                                Janusz Kajzer - Kabimec Consulting                                               Janusz Kajzer - Kabimec Consulting




                       Injuries to heart and arteries - 2                                                        Biomechanical Response

                                                                                                              Thoracic biomechanical response studies
                                                                                                                    - Volunteers
                                                                                                                    - Cadavers
                                                                                                                    - Animals (rabbits, dogs, monkeys, pigs)


                                                                                                              Types of cadaver thorax tests
                                                                                                                    - Impactor test
                                                                                                                    - Drop test
      Force from below to above on                   Injury to the heart and arteries: Neck                         - Sled test
      the right side can result in aortic            hyperextension and chest                                       - Full scale crash test
      tear just beyond left sub-clavian              compression
      artery




                                                                Janusz Kajzer - Kabimec Consulting                                               Janusz Kajzer - Kabimec Consulting



                                                                                                         Biomechanical Response - Techniques
         Biomechanical Response - Techniques                                                                 method developed to improve chest deflection
                                                                                                          measurements (12 accelerometers on the test subject)

               Determination of Thoracic Deflection:
                              - Deflectometer Rod
                              - Induction Coil Deflection Gage
                              - High Speed Film Analysis
                              - Chest Band (EPIDM) - External Peripheral
                                Instrument for Deformation Measurement
                                (Strain gage circuits mounted
                                on a steel band)




                                                                                               Sidan 3
                                                           Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting


       Force-deflection plots for quasi-static loading
                                                                                                    Frontal impact - biomechanical response
                                                                                                                    • frontal loading
                                                                                                                             – static loading ≠ dynamic loading
   Techniques to                                                                                                             – plateau influenced by impactor velocity
  Determine Thoracic                                                                                                         – high hysteresis
      Deflection
- Deflectometer Rod                                                                                                         Static loading                                             Dynamic loading
- Induction Coil
  Deflection Gage
- High Speed Film
  Analysis
- Chest Band (EPIDM)




                                                                                                based on: Lobdell T.E. "Impact response of the human thorax"                  from: Kroell, C.K.: "Thoracic response to blunt ~ron~al loading"




                                                           Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting



   Lateral impact - biomechanical response                                                           Lateral impact - biomechanical response




         Force Deflection Characteristics in Lateral Impacts with Flat                                                 Force Deflection Characteristics in Lateral Impacts with
                             Circular Impactor                                                                                            Padded Armrest




                                                           Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting




        Animals - biomechanical response                                                                                          Biomechanical response

                                                                                                        Lobdell thorax                            m1               m2               m3
                                                                                                        model:
                                                                                                                                              Impactor         Sternum part   Vertebral part



                                                                                                                          • Lobdell thorax model -> belt loading significantly
                       Force [kN]




                                                                                                                               different response than flat circular impactor


                                                                                                                          • animals experiment ->             level of the plateau force
                                                                                                                               correlates with weight of the animal
                                                                                                                          • lateral loading
                                                                                                                                  – lateral stiffness < frontal stiffness
                                                                                                                                  – plateau force less apparent
                                    % A-P Chest Diameter




                                                                                          Sidan 4
                                     Janusz Kajzer - Kabimec Consulting                                                         Janusz Kajzer - Kabimec Consulting



     Loading conditions of the chest
                                                                                        Injury criteria & tolerances

                                                                                 1: Chest deflection due to compression mechanism


                                                                                  • Compression Criterion (CC): maximum chest
                                                                                     compression is much better indicator of injury severity than
                                                                                     acceleration or force!
                                                                                       – frontal, blunt impact, quasi static: Vimp < 3 m/s
                               - Belt loading produces                                 – use normalized chest deflection: 35% deflection ->AIS 3

                                 significantly different                                           Compression Criterion (C)
                                 load distribution
                                                                                                            C = D/T th
                               - Dynamic thoracic                                                D = Deformation of the chest
                                 stiffness much larger                                           T th = Thickness of the chest




                                     Janusz Kajzer - Kabimec Consulting                                                         Janusz Kajzer - Kabimec Consulting




Why is chest deflection a better thoracic injury                                              Compression guide
     predictor than chest acceleration?

 • Chest compression directly relates chest
   loading to the risk of serious or fatal                                    Compression
   compression injury for the vital organs                                    • 20% Onset of rib fracture
   protected by the rib cage
 • Chest acceleration does not separate how much                              • 32% Tolerance for rib stability
   of the force is applied to the rib cage, shoulders                         • 40% Flail Chest
   or lumbar and cervical spine
                                                                              • 45% Sternum contacts spinal vertebrae
 • Distributed force can generate high thoracic
   acceleration with very little chest deformation




                                     Janusz Kajzer - Kabimec Consulting                                                         Janusz Kajzer - Kabimec Consulting



      Injury tolerance vs. thorax deflection                                        Compression criterion - story
         in frontal blunt thoracic impact
                                                                          • 1975: Neathery recommended a chest injury assessment value of
                                                                            76 mm -corresponding to a 50% risk of AIS3+ thoracic injury
                                                                          • 1984: Merz revised his maximum chest deflection from 75 mm to
                                                                            65 mm for blunt impact
                                                                          • 1988: Viano and Lau recommended 65 mm maximum chest
                                                                            deflection
                                                                          • 1988: Horsch found that the HIII chest may be much stiffer than the
                                                                            human chest in lower impact velocities, and therefore the
                                                                            recommended injury criteria of 65 mm was too high.
                                                                          • 1991: Merz found that 50 mm chest deflection corresponded to a
                                                                            40% risk of injury (seat belt loading)
                                                                          • 1991: Horsch et al. determined that 40mm chest deflection of a HIII
                                                                            was associated with a 25% risk of an AIS3+ injury (seat belt
                                                                            loading)
                                                                                                                             Kleinberger et al.,NHTSA, 1998.




                                                                    Sidan 5
                                                                Janusz Kajzer - Kabimec Consulting                                                                                                                      Janusz Kajzer - Kabimec Consulting




                     Injury criteria & tolerances                                                                                                       Severity Index (SI)
                2: Acceleration and force due to compression
                        mechanism & inertial loading

              • Single acceleration: <60 g at CG when t < 3 ms
                (Specified in United States regulations FMVSS
                208), limited validation
              • Chest severity index (SI): 1000 (not used, bad validation)
              • Force on the sternum: 3.3 kN =>minor injuries)
              • Distributed load shoulder + chest: 8.0 kN
                   => resulted in only minor injuries, compare F= 60 g (acc
                 criterion) * 30 kg (chest mass) = 18 kN
              • Thoracic Trauma Index (TTI)
                   – "+" mass, age
                   – "-" pure statistical function
                                                                                                                                                                                                                   (bad validation)




                                                                Janusz Kajzer - Kabimec Consulting                                                                                                                      Janusz Kajzer - Kabimec Consulting




                   Thoracic Trauma Index (TTI)                                                                                       Thoracic Trauma Index (TTI)
            • TTI = 1.4 * AGE + 0.5 * (RIBY + T12Y) * MASS / Mstd
               where:
               TTI =
               AGE =
                             Thoracic Trauma Index (dimension: g)
                             age of the subject in years
                                                                                                                            The tolerance level of a 50% probability for
               RIBY =        maximum absolute value of lateral acceleration in g's of                                       an AIS 4+ injury was found to be TTI = 170 g
                             the 4th and 8th rib on struck side after signal filtering
               T12Y =        maximum absolute value of lateral acceleration in g's of

               MASS=
                             the 12th thoracic vertebra after signal filtering
                             test subject mass in kg
                                                                                                                            The tolerance level of a 50% probability for
               Mstd =        standard reference mass of 75 kg                                                               an AIS 3+ injury was found to be TTI = 125 g
            • TTI(d) = 0.5 * (RIBY + T12Y)
               where:
               TTI(d) =      definition of the TTI used for 50th percentile dummies

Used as criterion in side impact in USA




                                                                Janusz Kajzer - Kabimec Consulting                                                                                                                      Janusz Kajzer - Kabimec Consulting


                     Injury criteria & tolerances                                                                                                 VC: ranges of validity
                    3: Viscous criterion due to compression
                        mechanism & viscous response


                                                     d [D(t )] D(t )
                            VC = V (t )∗C(t ) =               ∗
                                                        dt      D
                                                                            See: SAE J211

                • Viscous Criterion (VC) is a time function
                  formed by the product of the velocity of
                  deformation:V(t) and the instantaneous                                                                                Usable criterion:
                                                                                                                                                                    Com-
                                                                                                                                                                   pression
                                                                                                                                                                                    Viscous Criterion              Velocity

                  compression function:C(t)                                                                                                                                     3                             30               m/s
                    V(t) is calculated by differentiation of the deformation, and
                    C(t) is calculated in relation to initial torso thickness (D)                                                • less compression produce similar injury
                • valid if 3 m/s < Vimpact < 30 m/s                                                                                levels when impact velocity is increased!
                                                                                                     based on Lau I.V., Viano, D.C. "The Viscous Criterion: Bases and Applications of an Injury Severity Index for Soft Tissues"




                                                                                               Sidan 6
                                                                Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting




                          Viscous response                                                                                                        VC criterion

                                                                                                              • The tolerance level for a 25% probability of
  • Serious injury to soft tissue and organs                                                                    severe injury (AIS 4+) was found to be
    occurs at the time of peak viscous response,                                                                VCmax = 1 m/s
    well before maximum deflection
                                                                                                              • VC has been criticized that it is a measure of
  • The maximum chest compression is needed                                                                     the energy stored in the thorax and not the
                                                                                                                energy dissipated
    to protect against crushing injuries, which
    may occur during slow or static deformation
    of the chest and abdomen                                                                                  • It has also been hypothized that varied
                                                                                                                loading conditions by different restraints
                                                                                                                need a more restraint specific injury criterion




                                                                Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting




     Combined Thoracic Index (CTI) - 1                                                                             Combined Thoracic Index (CTI) - 2




A max = Maximum chest acceleration (g)
A int = X-axis intercept (dummy specific), 85 g’s for 50% HIII
D max = Maximum chest deflection (mm)
D int = Y-axis intercept (dummy specific), 102 mm for 50% HIII
                                                                                                     Kleinberger et al.,”Development of improved injury criteria for the assessment of
                                                                                                     advanced automotive restraint systems”, NHTSA, 1998.




                                                                Janusz Kajzer - Kabimec Consulting                                                                                       Janusz Kajzer - Kabimec Consulting



   Thorax: Frontal impact injury tolerances                                                                       Thorax: Lateral impact injury tolerances
                                                                                                                         Tolerance level                          Injury level                      Reference
                                                                                                              Force ( kN)
          Tolerance level               Injury level                     Reference                               7.4Ńdrop test                      AIS = 0                                 Tarrierre et al. (1979)
                                                                                                                 l 0.2Ńdrop test                    AIS = 3                                 Tarrierre et al . (1979)
   Force                                                                                                         5.5Ńpendulum impact                25% probability of AIS 4                Viano (1989)
    3.3 kN to sternum        Minor injury                      Patrick et al. (1969)
                                                                                                              Acceleration (g's)
    8.8 kN to chest and      Minor injury                      Patrick et al. (1969)
                                                                                                                 45.2g T8y                          25% probability of AIS 4                Viano (1989)
   shoulders
                                                                                                                 31.6 g T12y                        25% probability of AIS 4                Viano (1989)
                                                                                                                 27.7g Upper sternum-X              25% probability of AIS 4                Cavanaugh et al. (1990)
   Acceleration (g's)
    60                       3 ms limit for Hybrid II & III    FMVSS 208                                      TTI(d) (g's)
   Deflection (mm)                                                                                               85                                 Max. in SID dummy for 4-door cars       FMVSS 214
    58                       No rib fracture                   Stalnaker and Mohan ( 1974)                       90                                 Max. in SID dummy for 2-door cars       FMVSS 214
    76                       Limit for Hybrid III              FMVSS 208                                      Compression (%) to half thorax
   Compression (%)                                                                                               35                                 AIS 3                                   Stalnaker et al. (1979)
    20                       Onset of rib fracture            Kroell et al. (1971, 1974)                         35                                 AIS 3                                   Tarrierre et al. (1979)
    40                       Flail chest                      Kroell et al. ( 1971, 1974)                        31 (includes arm)                  25% probability of AIS 4                Cavanaugh et al. (1990)
    32                       Tolerance for rib cage stability Viano (1978)                                    Compression (%) to whole thorax
   VCmax (m/s)                                                                                                   38.4                               25% probability of AIS 4                Viano (1989)
    1.0                      25% probability of AIS >3         Viano and Lau (1985)                           VCmax (m/s) to half thorax
    1.3                      50% probability of AIS >3         Viano and Lau (1985)                              < 1.0                              AIS 0-2
                                                                                                                 >1.0                               AIS 4,5                                 Cavanaugh et al. (1990)
                                                                                                                                                                                            and unpublished data
                                                                                                              VCmax (m/s) to whole thorax
                                                                                                                1.47                                25% probability of AIS 4                Viano (1989)




                                                                                               Sidan 7
                                                       Janusz Kajzer - Kabimec Consulting                                        Janusz Kajzer - Kabimec Consulting




           Thorax - Crash Safety Legislation                                                        Good or bad thorax injury
                                                                                                           predictors
     Frontal Collision EU (96/79/EG)         Frontal Collision USA (FMVSS 208)
                                                                                            • The TTI has been widely criticized since
Thorax Compression Criterion (ThCC): 50 mm
Soft Tissue Criterion (VC): 1.0 m/s
                                              50% HII
                                              Chest acceleration: 60 g
                                                                                              acceleration is not a good measurement of soft
                                              Thorax compression: 63 mm                       tissue injuries to the chest and the abdomen
                                              5% HII                                        • Serious internal injury can occur without a
                                              Chest acceleration: 60 g
                                              Thorax compression: 52 mm                       significant number of rib fractures or rib cage
                                                                                              injury at all
     Side Collision EU (96/27/EG)            Side Collision USA (FMVSS 214)
  RDC (Rib Deflection): 42 mm                 Thoracic Trauma Index (TTI):
                                                                                            • In a cadaver study it was found that acceleration
  Soft tissue criterion (VC): 1.0 m/s         85 g (4-door)                                   or force-based injury criteria did not predict injury
                                              90 g (2-door)
                                                                                              as well as compression and VC




                                                       Janusz Kajzer - Kabimec Consulting                                        Janusz Kajzer - Kabimec Consulting




 Chest injury assessment values in frontal impact                                                 Chest injury assessment values
               for the HIII dummies                                                                 for Side-Impact Dummies




                                                       Janusz Kajzer - Kabimec Consulting




                                                                                      Sidan 8

				
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