An examination of American football helmets using brain deformation metrics associated with concussion (original) (raw)
Related papers
Concussion has become recognized as an injury which can be a source of long term neurological damage. This has led to research into which metrics may be more appropriate to define risk of injury. Some researchers support the use of linear acceleration as a metric for concussion, while others suggest the use of linear and rotational acceleration as well as brain deformation metrics. The purpose of this study was to examine the relationships between these metrics using a centric and non-centric impact protocol. A linear impactor was used to impact a Hybrid III headform fitted with different models of American football helmet using a centric and non-centric protocol. The dynamic response was then used as input to the FE model for analysis of brain deformations. The results showed that linear acceleration was correlated to rotational acceleration and brain deformation for centric conditions, but under non-centric conditions it was not. These results indicate that the type of methodology used will influence the relationship between the variables used to assign risk of concussion. These results also support the use of a centric/non-centric protocol and measurement of rotational acceleration and brain deformation when it comes to the development of helmet technologies.
Neurosurgical Focus, 2012
Object The authors' goal was to better define the relationship between biomechanical parameters of a helmeted collision and the likelihood of concussion. Methods The English-language literature was reviewed in search of scholarly articles describing the rotational and translational accelerations observed during all monitored impact conditions that resulted in concussion at all levels of American football. Results High school players who suffer concussion experience an average of 93.9g of translational acceleration (TA) and 6505.2 rad/s2 of rotational acceleration (RA). College athletes experience an average of 118.4g of TA and 5311.6 rad/s2 of RA. While approximately 3% of collisions are associated with TAs greater than the mean TA associated with concussion, only about 0.02% of collisions actually result in a concussion. Associated variables that determine whether a player who experiences a severe collision also experiences a concussion remain hypothetical at present. Conclusio...
Ice hockey is a contact sport which has a high incidence of brain injury. The current methods of evaluating protective devices use peak resultant linear acceleration as their pass/fail criteria, which are not fully representative of brain injuries as a whole. The purpose of this study was to examine how the linear and angular acceleration loading curves from a helmeted impact influence currently used brain deformation injury metrics. A helmeted Hybrid III headform was impacted in five centric and non-centric impact sites to elicit linear and angular acceleration responses. These responses were examined through the use of a brain model. The results indicated that when the helmet is examined using peak resultant linear acceleration alone, they are similar and protective, but when a 3D brain deformation response is used to examine the helmets, there are risks of brain injury with lower linear accelerations which would pass standard certifications for safety.
Rotational Head Kinematics in Football Impacts: An Injury Risk Function for Concussion
Annals of Biomedical Engineering, 2011
Recent research has suggested a possible link between sports-related concussions and neurodegenerative processes, highlighting the importance of developing methods to accurately quantify head impact tolerance. The use of kinematic parameters of the head to predict brain injury has been suggested because they are indicative of the inertial response of the brain. The objective of this study is to characterize the rotational kinematics of the head associated with concussive impacts using a large head acceleration dataset collected from human subjects. The helmets of 335 football players were instrumented with accelerometer arrays that measured head acceleration following head impacts sustained during play, resulting in data for 300,977 subconcussive and 57 concussive head impacts. The average subconcussive impact had a rotational acceleration of 1230 rad/ s 2 and a rotational velocity of 5.5 rad/s, while the average concussive impact had a rotational acceleration of 5022 rad/ s 2 and a rotational velocity of 22.3 rad/s. An injury risk curve was developed and a nominal injury value of 6383 rad/s 2 associated with 28.3 rad/s represents 50% risk of concussion. These data provide an increased understanding of the biomechanics associated with concussion and they provide critical insight into injury mechanisms, human tolerance to mechanical stimuli, and injury prevention techniques.
The influence of velocity on the performance range of American football helmets
2013
Concussion has become a prevalent injury in the sport of American football. The nature of this injury can be influenced by the mass of the impactor, velocity, compliance, and direction of impact. As a result it is important to characterize how American football helmets perform against these impact characteristics. The purpose of this research is to examine how an American football helmet performs across velocities and impact angles which can occur in the sport of American football. The methods used a combination of Hybrid III headform impacts combined with a finite element modeling approach to find the brain deformation variables known to be associated with concussion. The results indicated that the American football helmets performed best at 5.5 and 7.5 m/s. At 9.5 m/s the brain deformation metrics showed a sharp increase in risk of concussion. Also, the region of the brain with the largest magnitude deformation shifted with differing velocities. The results indicate that current football helmet designs should expand the energy absorbing capacity of the shell and liner to accommodate these impact conditions.
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2014
Concussion has become a prevalent injury in the sport of American football, and its severity can be influenced by the mass of the impactor, velocity, compliance, and direction of impact. As a result, it is important to characterize how American football helmets perform against these impact characteristics. The purpose of this research is to examine how an American football helmet performs across velocities and impact angles which can occur in the sport of American football. The methods used a combination of Hybrid III headform impacts combined with a finite element modeling approach to find the brain deformation variables known to be associated with concussion. At the 9.5 m/s impacts, the brain deformation metrics showed an increase in risk of concussion. Also, the region of the brain with the largest magnitude deformation shifted with differing velocities when analyzed using maximum principal strain but not von Mises stress. The results indicate that impact conditions (location and...
Finite element modeling of human brain response to football helmet impacts
Computer methods in biomechanics and biomedical engineering, 2016
The football helmet is used to help mitigate the occurrence of impact-related traumatic (TBI) and minor traumatic brain injuries (mTBI) in the game of American football. While the current helmet design methodology may be adequate for reducing linear acceleration of the head and minimizing TBI, it however has had less effect in minimizing mTBI. The objectives of this study are (a) to develop and validate a coupled finite element (FE) model of a football helmet and the human body, and (b) to assess responses of different regions of the brain to two different impact conditions - frontal oblique and crown impact conditions. The FE helmet model was validated using experimental results of drop tests. Subsequently, the integrated helmet-human body FE model was used to assess the responses of different regions of the brain to impact loads. Strain-rate, strain, and stress measures in the corpus callosum, midbrain, and brain stem were assessed. Results show that maximum strain-rates of 27 and...
Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 2012
This research was undertaken to examine a new method for assessing the performance of ice hockey helmets. It has been proposed that the current centric impact standards for ice hockey helmets, measuring peak linear acceleration, have effectively eliminated traumatic head injuries in the sport, but that angular acceleration and brain tissue deformation metrics are more sensitive to the conditions associated with concussive injuries, which continue to be a common injury. Ice hockey helmets were impacted using both centric and non-centric impact protocols at 7.5 m/s using a linear impactor. Dynamic impact responses and brain tissue deformations from the helmeted centric and non-centric head form impacts were assessed with respect to proposed concussive injury thresholds from the literature. The results of the helmet impacts showed that the method used was sensitive enough to distinguish differences in performance between helmet models. The results have shown that peak linear acceleration yielded low magnitudes of response to an impact, but peak angular acceleration and brain deformation metrics consistently reported higher magnitudes, reflecting a high risk for incurring a mild traumatic brain injury.
Concussion in Professional Football: Brain Responses by Finite Element Analysis: Part 9
Neurosurgery, 2005
OBJECTIVE: Brain responses from concussive impacts in National Football League football games were simulated by finite element analysis using a detailed anatomic model of the brain and head accelerations from laboratory reconstructions of game impacts. This study compares brain responses with physician determined signs and symptoms of concussion to investigate tissue-level injury mechanisms. METHODS: The Wayne State University Head Injury Model (Version 2001) was used because it has fine anatomic detail of the cranium and brain with more than 300,000 elements. It has 15 different material properties for brain and surrounding tissues. The model includes viscoelastic gray and white brain matter, membranes, ventricles, cranium and facial bones, soft tissues, and slip interface conditions between the brain and dura. The cranium of the finite element model was loaded by translational and rotational accelerations measured in Hybrid III dummies from 28 laboratory reconstructions of NFL impacts involving 22 concussions. Brain responses were determined using a nonlinear, finite element code to simulate the large deformation response of white and gray matter. Strain responses occurring early (during impact) and mid-late (after impact) were compared with the signs and symptoms of concussion. RESULTS: Strain concentration "hot spots" migrate through the brain with time. In 9 of 22 concussions, the early strain "hot spots" occur in the temporal lobe adjacent to the impact and migrate to the far temporal lobe after head acceleration. In all cases, the largest strains occur later in the fornix, midbrain, and corpus callosum. They significantly correlated with removal from play, cognitive and memory problems, and loss of consciousness. Dizziness correlated with early strain in the orbital-frontal cortex and temporal lobe. The strain migration helps explain coup-contrecoup injuries. CONCLUSION: Finite element modeling showed the largest brain deformations occurred after the primary head acceleration. Midbrain strain correlated with memory and cognitive problems and removal from play after concussion. Concussion injuries happen during the rapid displacement and rotation of the cranium, after peak head acceleration and momentum transfer in helmet impacts.