Doug Browne Jeff Markle Tyler Severance

 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?

 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/s 2

 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

 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.

 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

 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

 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

 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 + = + ?

 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

 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

 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

 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

 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

 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

 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

 Huang HM, Lee MC, Chiu WT, Chen CT, Lee SY: Three-dimensional finite element analysis for subdural hematoma. J Trauma 47: 538–544,  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): , 2006.Journal of Neurosurgery  Löwenhielm P: Strain tolerance of the vv. cerebri sup. (BVs) calculated from head-on collision tests with cadavers. Z Rechtsmedizin 75:131–144,  Gennarelli TA, Thibault LE: Biomechanics of acute subdural hematoma. J Trauma 22:680–686,  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

 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): ,  Forbes JA, Withrow TJ: Biomechanics of Subdural Hemorrhage in American Football. Vanderbilt University, 2010

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