Using human body models to evaluate the efficacy of cervical collars in cervical instability

Transcription

1 Using human body models to evaluate the efficacy of cervical collars in cervical instability Karin Brolin Department of Mechanics and Maritime Sciences Chalmers University of Technology

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4 Real world safety Primary prevention Develop safety systems Assess safety Test prototypes CAE design Numerical tools Experimental tests Crash dummies Human body models Research Aim: To provide useful numerical methods and human body models that are biofidelic for a large range of loading scenarios and that can predict injury.

5 Recent HBM projects Active muscles Prediction of thoracic, brain and lumbar spine injury risks Average female HBM Adipose tissue Active muscles in child HBMs Brain injury criteria

6 ExtricAction Pre-Study PhD. Jonas Östh

7 Introduction Extrication of motor crash victims in general concerned with Speed of extrication crucial to reduce risk of fatality (Calland 2005) Cervical immobilization routinely performed to avoid secondary injury, although positive effects have not been proven (Sundstrøm et al. 2014) Published biomechanical studies on the effect of cervical collars either with volunteers or human cadavers Aim Simulate one previously published study (Ben-Galim et al. 2010)

8 Case study Ben-Galim et al Investigated the effect of a cervical immobilization collar in the presence of a severe dissociative injury 9 PMHS subjects (66 88 years old)

9 Methods: Numerical HBM GHBMC 50th percentile male occupant model v4.1.1 (Elemance, Winston-Salem, NC) 2.2 million elements 1.25 million nodes Published validation: Segment-level force-deflection characteristics (Panzer and Cronin 2009) Tissue-level failure prediction (DeWit and Cronin 2012) Capsular-ligament response (Fice et al. 2011)

10 Methods: Simulated injury Ben-Galim et al. (2010) : Fractured dens at its base Severed nuchal, left and right capsular ligaments, tectorial membrane, inferior cruciate ligament, and anterior longitudinal ligament

11 Methods: Loading to represent cervical collar. Model reduced for computational efficiency Soft tissues and bones below T1 level constrained to move Head displaced vertically 11.3 mm 4 simulations Uninjured Uninjured with 20% muscle activation Injured Injured with 20% muscle activation

12 Results Uninjured Injured

13 Δ P =1.34 mm Δ A =1.95 mm Δ P =3.11 mm Δ A =7.81 mm Uninjured Injured

14 Effect of 20% Muscle Activation Anterior Distraction (mm) Uninjured Uninjured 20% muscle activation Injured Injured 20% muscle activation Posterior Anterior Posterior Distraction (mm) Uninjured Uninjured 20% muscle activation Injured Injured 20% muscle activation Effect of MA: More C1 C2 distraction More anterior increase than posterior in injured case

15 Discussion Similar to PMHS results most distraction happens at weakest point (site of injury) The effect of muscle contraction can be studied (in contrast to PMHS) 20% activation more separation at site of injury Local stretch reflex muscle response likely more relevant to study Spinal cord injury risk was not assessed in PMHS study Could be evaluated by inclusion of spinal cord in model and assessment of tissue strain.

16 Discussion cont. Human Body Models needs to be validated with respect to physical test data can be a difficult process However, once model is validated parameter studies are very easy to perform Levels of collar tension, correlated with for instance spinal cord strain

17 Recent HBM projects Active muscles Prediction of thoracic, brain and lumbar spine injury risks Average female HBM Adipose tissue Active muscles in child HBMs Brain injury criteria

18 SAFER Active Human Body Model A HBM step 3 Biofidelic HBM for simulation of sequences of events: combined emergency and crash events run off road events other long duration crash events

19 SAFER A HBM in Braking events Autonomous braking* Driver braking** * Östh J, Brolin K, Bråse D. A Human Body Model with Active Muscles for Simulation of Pre Tensioned Restraints in Autonomous Braking Interventions. Traffic Injury Prevention, 16 (3) s , ** Östh J, Eliasson E, Happee R, Brolin K. A Method to Model Anticipatory Postural Control in Driver Braking Events, Gait & Posture. 40 (4) s , 2014.

20 Omni directional SAFER A HBM

21 Improved injury prediction using HBM, step 3 Biofidelic HBM that can predict thoracic, brain and lumbar spine injury risks

22 Rib strain validation 1. Single rib tests 2a. Table top tests 2b. Impactor tests Fringe=maximum principal strain Fringe=maximum principal strain Fringe=maximum principal strain Kindig, M.W., (2009). Tolerance to failure and geometric influences on the stiffness of human ribs under anteriorposterior loading, Thesis, School of Engineering and Applied Science University of Virginia. Shaw, C.G., Lessley, D., Evans, J., Crandall, J.R., Shin, J., Portier, P., Paolomi, G., (2007). Quasi static and dynamic thoracic loading tests: Cadaveric torsos. In: Proceedings of the Proceedings of the International Research Council on the Biomechanics of Injury conference. Trosseille, X., Baudrit, P., Leport, T., Vallancien, G., (2008). Rib cage strain pattern as a function of chest loading configuration. Stapp car crash journal 52,

23 Rib strain validation / Injury criteria evaluation 3. Sled tests 4. Accident reconstructions...back to V [km/h] Airbag trig time [ms] Angle [deg] 1.0 Fringe=maximum principal strain P(AIS3+ rib fracture) AGE=30 AIS Crandall, J., (2012). Atd thoracic response test development gold standard buck condition 2: Force limited belt, 30 km/h frontal (Report), Charlottesville, Virginia, University of Virginia. Iraeus, J., (2015). Stochastic finite element simulations of real life frontal crashes. Doctoral thesis, comprehensive summary. Umeå University Winsmash V [km/h] NASS/CDS Simulation

24 ViVA II Virtual Vehicle Safety Assessment To reduce transport gender inequality. Create an open source virtual HBM of an average female. Propose a virtual test method protocol seat assessment.

25 ViVA OpenHBM female model

26 Acknowledgements The presented work has been carried out in association with SAFER Vehicle and Traffic Safety Centre at Chalmers, Sweden. Simulation resources have been supplied by C3SE.

27 Questions?

28 References Ben-Galim P, Dreiangel N, Mattox KL, Reitman CA, Kalantar SB, Hipp JA (2010) Extrication Collars Can Result in Abnormal Separation Between Vertebrae in the Presence of a Dissociative Injury. Journal of Trauma 69(29): Calland V (2005) Extrication of the Seriously Injured Road Crash Victim. Emergency Medicine Journal 22(8): DeWit J, Cronin D (2012) Cervical Spine Segment Finite Element Model for Traumatic Injury Prediction, J Mech Behav Biomed Mater. 10: Fice J, Cronin D, Panzer M. (2011) Cervical Spine Model to Predict Capsular Ligament Response in Rear Impact, Ann Biomed Eng. 39(8): Östh J. (2014) Muscle Responses of Car Occupants: Numerical Modeling and Volunteer Experiments under Pre- Crash Braking Conditions. PhD Thesis, Gothenburg Sweden: Chalmers University of Technology. Panzer M, Cronin D. (2009) C4 C5 Segment Finite Element Model Development, Validation, and Load-Sharing Investigation, J Biomech. 42(4): Sundstrøm T, Asbjørnsen, Habiba S, Sunde GA, Wester K (2014) Prehospital Use of Cervical Collars in Trauma Patients: A Critical Review. Journal of Neurotrauma 31: Yoganandan N, Pintar FA, Maiman J, Cusick JF, Sances A Jr, Walsh PS (1996) Human Head-Neck Biomechanics under Axial Tension, Medical Engineering Physics 18;