Football Helmet (system) to Reduce Subdural Hemorrhaging by Mitigating Rotational Acceleration

1. Doug Browne Jeff Markle Tyler Severance Football Helmet (system) to Reduce Subdural Hemorrhaging by Mitigating Rotational Acceleration

2. What Causes Subdural Hemorrhage? • Subdural hemorrhaging occurs when the blood vessels that connect the dura to the brain rupture • This can happen when the brain moves relative to the dura, causing the connecting vessels to stretch and burst • Due to a higher density of CSF relative to brain tissue density (4% greater) • How much strain would be significant?

3. Rotational Acceleration • From cadaveric studies at Vanderbilt University, the connecting blood vessels undergo permanent deformation at 120% strain and total rupture at 150% strain which occurs at accelerations between 4,500 and 10,000 rad/s2

4. Rotational Acceleration Dangers in American Football • Well verified that collisions in football can exceed dangerous levels of rotational acceleration • In all levels of football (high school, college and professional) the top 1% of collisions far exceed critical levels of rotational acceleration • Collisions cannot be prevented without drastic change in the sport; however, helmet design can be modified to protect against the potential risk

5. NOCSAE • The National Operating Committee on Standards for Athletic Equipment is the governing body that regulates standards for football helmets. • Helmets are only required to prevent against levels of translational acceleration that would cause skull fractures.

6. Helmet Design Problems • Visited Southern Impact Research Center to meet with Dave Halstead, one of the nation’s leading experts on helmet design • Additionally, Halstead explained and showed that concussions can occur without contact to the head • Jason Witten example showcased this well • Current helmets are effective at dampening blows to the head (difficult to improve upon), but this is a different issue than lowering overall angular acceleration

7. First Steps • After meeting with Mr. Halsted, it was necessary to redefine the parameters of the issue and start brainstorming new solutions • Together, we identified three main issues our team could “tackle” • Helmet weight • Relatively large range of motion • Detection of dangerous accelerations

8. New Helmet Design • Lightweight helmet that keeps similar levels of protection against linear acceleration as current models • Include in the helmet a device that indicates when dangerous levels of rotational acceleration have been reached. • Attempt to create a seat belt based design to prevent the head from reaching the peak levels during the collision

9. Initial Plan • The seat belt theory has potential, but a helmet alone won’t regulate the motion • Shoulder pads can be included to transform the system from just a head to the entire upper torso • Perhaps it will be possible to tether the helmet to the pads + + ? =

10. Other Possibilities • Another issue that can be addressed is that a significant number of subdural hemorrhages are undetected (sources vary widely on actual number) • Possible to create a safety feature that would indicate when dangerous levels of acceleration have been reached • Apply an accelerometer to the back of the helmet which could signal that a player should be removed from play and examined by a professional Shok-SpotR will serve as both a cost effective and functional accelerometer for the needs of our helmet

11. Failure • First prototype cannot succeed • Simple football constraints make it impractical • The tethering system cannot be placed in front of the pads. • Would be destroyed quickly • Otherwise impractical • Unfortunately, our intended pulley system (to place pads on the back) isn’t feasible either • After experimenting with this, the group decided to abandon this plan

12. Two new possibilities • Screen door closers use a dashpot to reduce acceleration when closing • Example of controlled angular deceleration • Viscoelastic based properties • Might be possible to use network of these (shoulder pad = origin; helmet = insertion) to restrict but not inhibit quick movements

13. Two new possibilities • Spring coiled safety door closers also control the reduction of acceleration • The spring network provides greater resistance the more the system is stretched • Downside is that the spring is very one dimensional

14. Prototype #2 • Spring loaded design • Team purchased one to continue progress • Incorporate the padding system of a butterfly collar • Used in 3 different directions • One on each side and one in the back • Helmet would rest in between the padding network • Allow movement, inhibit rapid acceleration • *** Helmet and Shoulder pads are a separate network… still are easy to remove and separate

15. Obstacles • After working with the recently purchased parts, only one clear difficulty thus far… • Weight • Spring networks are heavier than expected so it will be necessary to eliminate weight from other parts of the design

16. Steps to come • If all goes as planned, we will have a working prototype that can be tested by the end of March • Further testing and modification can occur as needed for the rest of the semester

17. References • Huang HM, Lee MC, Chiu WT, Chen CT, Lee SY: Three-dimensional finite element analysis for subdural hematoma. J Trauma 47: 538–544, 1999. • Depreitere B, Van Lierde C, Vander Sloten J, Van Audekercke R, Van Der Perre G, Plets C et al.: Mechanics of acute subdural hematomas resulting from BV rupture. Journal of Neurosurgery 104(6): 950-956, 2006. • LöwenhielmP: Strain tolerance of the vv. cerebri sup. (BVs) calculated from head-on collision tests with cadavers. Z Rechtsmedizin75:131–144, 1974. • GennarelliTA, Thibault LE: Biomechanics of acute subdural hematoma. J Trauma 22:680–686, 1982. • Lee MC, Ueno K, Melvin JW: Finite element analysis of traumatic subdural hematoma, in Proceedings of the 31st Stapp Car Crash Conference. New York, NY, Society of Automotive Engineers, 1987, pp 67-77.

18. References Con’t • Lee MC, Haut RC: Insensitivity of tensile failure properties of human BVs to strain rate: implication in biomechanics of subdural hematoma.J Biomech 22(6-7): 537-42, 1989. • Forbes JA, Withrow TJ: Biomechanics of Subdural Hemorrhage in American Football. Vanderbilt University, 2010

19. Final Note: • To learn more about Southern Impact Research Center, please visit: • http://www.youtube.com/watch?v=hwA-hiFu4Xw • http://www.soimpact.com/