Now showing 1 - 10 of 21
  • Publication
    Determining the relationship between linear and rotational acceleration and MPS for different magnitudes of classified brain injury risk in ice hockey
    (International Research Council on the Biomechanics of Injury (IRCOBI), 2015-09-11) ; ; ;
    Helmets have successfully decreased the incidence of traumatic brain injuries (TBI) in ice hockey, yet the incidence of concussions has essentially remained unchanged. Current ice hockey helmet certification standards use peak linear acceleration as the principal measuring helmet performance, however peak linear acceleration may not be an appropriate variable to evaluate risk at all magnitudes of brain injury. The purpose of this study is to determine the relationship between linear acceleration, rotational acceleration and maximum principal strain (MPS) for different magnitudes of classified brain injury risk in ice hockey. A helmeted and unhelmeted Hybrid III headform were impacted to the side of the head at two sites and at three velocities under conditions representing three common mechanisms of injury. Resulting linear and rotational accelerations were used as input for the University College Dublin Brain Trauma Model (UCDBTM), to calculate MPS in the brain. The resulting MPS magnitudes were used to separate the data into three groups: low risk; concussion; and TBI. The results demonstrate that the relationship between injury metrics in ice hockey impacts is dependent on the magnitude of classified injury risk and the mechanism of injury.
  • Publication
    Effect of impact surface in equestrian falls
    (International Society of Biomechanics in Sports (ISBS), 2016-07-22) ; ; ; ;
    This study examines the effect of impact surface on head kinematic response and maximum principal strain (MPS) for equestrian falls. A helmeted Hybrid III headform was dropped unrestrained onto three impact surfaces of different stiffness (steel, turf and sand) and three locations. Peak resultant linear acceleration, rotational acceleration and duration of the impact events were measured. A finite element brain model was used to calculate MPS. The results revealed that drops onto steel produced higher peak linear acceleration, rotational acceleration and MPS but lower impact durations than drops to turf and sand. However, despite lower MPS values, turf and sand impacts compared to steel impacts still represented a risk of concussion. This suggests that certification standards for equestrian helmets do not properly account for the loading conditions experienced in equestrian accidents.
  • Publication
    The Association among Injury Metrics for Different Events in Ice Hockey Goaltender Impact
    (International Research Council on Biomechanics of Injury (IRCOBI), 2016-09-16) ; ; ;
    Current ice hockey goaltender helmet standards use a drop test and peak linear acceleration to evaluate performance. However, ice hockey goaltenders are exposed to impacts from collisions, falls and pucks which each create unique loading conditions. As a result, the use of peak linear acceleration as a predictor for brain trauma in current ice hockey standards may not be most appropriate. The purpose of this study was to determine how kinematic response measures correlate to maximum principal strain and von Mises stress for different impact events. A NOCSAE headform was fitted with three ice hockey goaltender helmet models and impacted under conditions representing these three different impact events (fall, puck, collision). Peak resultant linear acceleration, rotational acceleration and rotational velocity of the headform were measured. Resulting accelerations were input into the University College Dublin Brain Trauma Model, which calculated maximum principal strain and von Mises stress in the cerebrum. The results demonstrated that the relationship between injury metrics in ice hockey goaltender impacts is dependent on the impact event and velocity. As a result of these changing relationships, the inclusion of finite element analysis in test protocols may provide a more practical representation of brain loading in evaluating the performance of ice hockey goaltender helmets.
  • Publication
    The dynamic response characteristics of traumatic brain injury
    Traumatic brain injury (TBI) is a common injury and is a leading cause of morbidity and mortality throughout the world. Research has been undertaken in order to better understand the characteristics of the injury event and measure the risk of injury to develop more effective environmental, technological, and clinical management strategies. This research used methods that have limited applications to predicting human responses. This limits the current understanding of the mechanisms of TBI in humans. As a result, the purpose of this research was to examine the characteristics of impact and dynamic response that leads to a high risk of incurring a TBI in a human population. Twenty TBI events collected from hospital reports and eyewitness accounts were reconstructed in the laboratory using a combination of computational mechanics models and Hybrid III anthropometric dummy systems. All cases were falls, with an average impact velocity of approximately 4.0 m/s onto hard impact surfaces. The results of the methodology were consistent with current TBI research, describing TBI to occur in the range of 335 to 445 g linear accelerations and 23.7 to 51.2 krad/s2 53 angular accelerations. More significantly, this research demonstrated that lower responses in the antero-posterior direction can cause TBI, with lateral impact responses requiring larger magnitudes for the same types of brain lesions. This suggests an increased likelihood of incurring TBI for impacts to the front or back of the head, a result that has implications affecting current understanding of themechanisms of TBI and associated threshold parameters.
  • Publication
    A Comparison of dynamic impact response and brain deformation metrics within the cerebrum of head impact reconstructions representing three mechanisms of head injury in ice hockey
    (International Research Council on the Biomechanics of Injury, 2012) ; ;
    Ice hockey has been identified as having one of the highest concussion rates. The three most likely causes of concussive injury are; falls to the ice, shoulder to head impacts and punches to the head. The purpose of this study was to examine how these three mechanisms of injury in the sport of ice hockey influence the dynamic response of the head form and the magnitude and distribution of maximum principal strain in the cerebrum. The three impact mechanisms were simulated using a Hybrid III head and neck form attached to a linear impactor, pendulum or monorail system. Three dimensional linear and rotational acceleration data from each impact condition were used to undertake finite element modeling to calculate maximum principal strain in regions of brain tissue. The results indicated that each mechanism incurred a unique peak resultant linear and rotational acceleration response. The maximum principal strain magnitudes were found to be largest in the fall to the ice. The regions of the brain incurring the largest deformation varied per mechanism of injury. This variation of peak magnitude per brain region might explain the differences in symptomology for concussion. Furthering the understanding of these mechanisms would aid in improving the safety of the game.
  • Publication
    The influence of centric and non-centric impacts to American football helmets on the correlation between commonly metrics in brain injury research
    (International Research Council on the Biomechanics of Injury, 2012) ; ; ;
    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.
  • Publication
    Comparison of Ice Hockey Goaltender Helmets for Concussion Type Impacts
    Concussions are among the most common injuries sustained by ice hockey goaltenders and can result from collisions, falls and puck impacts. However, ice hockey goaltender helmet certification standards solely involve drop tests to a rigid surface. This study examined how the design characteristics of different ice hockey goaltender helmets affect head kinematics and brain strain for the three most common impact events associated with concussion for goaltenders. A NOCSAE headform was impacted under conditions representing falls, puck impacts and shoulder collisions while wearing three different types of ice hockey goaltender helmet models. Resulting linear and rotational acceleration as well as maximum principal strain were measured for each impact condition. The results indicate that a thick liner and stiff shell material are desirable design characteristics for falls and puck impacts to reduce head kinematic and brain tissue responses. However for collisions, the shoulder being more compliant than the materials of the helmet causes insufficient compression of the helmet materials and minimizing any potential performance differences. This suggests that current ice hockey goaltender helmets can be optimized for protection against falls and puck impacts. However, given collisions are the leading cause of concussion for ice hockey goaltenders and the tested helmets provided little to no protection, a clear opportunity exists to design new goaltender helmets which can better protect ice hockey goaltenders from collisions.
      521Scopus© Citations 8
  • Publication
    An examination of American football helmets using brain deformation metrics associated with concussion
    The sport of American football is associated with a high incidence of concussion, which research has identified may lead to long term neurological damage. As a result, it is important that protective technologies be developed to help mitigate the incidence of this type of brain trauma. This research examines how the design characteristics between different American football helmet models affect the linear and rotational acceleration responses as well as brain deformation metrics using a centric/non-centric impacting protocol. The protocol involved impacting the helmets at nine centric/non-centric sites. Brain deformation metrics were calculated using the University College Dublin Brain Trauma Model. The results revealed that design characteristics do influence the brain deformation metrics associated with incidence of concussion. Further analysis revealed that rotational acceleration was more related to brain deformation metrics than linear acceleration. These results show that when attempting to reduce brain deformation metrics, the development of rotational acceleration diminishing technologies may be beneficial. This research indicates that helmet design may be able to reduce the risk of concussive injury.
      1343Scopus© Citations 48
  • Publication
    Characterization of persistent concussive syndrome using injury reconstruction and finite element modelling
    Concussions occur 1.7 million times a year in North America, and account for approximately 75% of all traumatic brain injuries (TBI). Concussions usually cause transient symptoms but 10 to 20% of patients can have symptoms that persist longer than a month. The purpose of this research was to use reconstructions and finite element modeling to determine the brain tissue stresses and strains that occur in impacts that led to persistent post concussive symptoms (PCS) in hospitalized patients. A total of 21 PCS patients had their head impacts reconstructed using computational, physical and finite element methods. The dependent variables measured were maximum principal strain, von Mises stress (VMS), strain rate, and product of strain and strain rate. For maximum principal strain alone there were large regions of brain tissue incurring 30 to 40% strain. This large field of strain was also evident when using strain rate, product of strain and strain rate. In addition, VMS also showed large magnitudes of stress throughout the cerebrum tissues. The distribution of strains throughout the brain tissues indicated peak responses were always present in the grey matter (0.481), with the white matter showing significantly lower strains (0.380) (p<0.05). The impact conditions of the PCS cases were severe in nature, with impacts against non-compliant surfaces (concrete, steel, ice) resulting in higher brain deformation. PCS biomechanical parameters were shown to fit between those that have been shown to cause transient post concussive symptoms and those that lead to actual pathologic damage like contusion, however, values of all metrics were characterized by large variance and high average responses. This data supports the theory that there exists a progressive continuum of impacts that lead to a progressive continuum of related severity of injury from transient symptoms to pathological damage.
      465Scopus© Citations 52
  • Publication
    Evaluation of the protective capacity of baseball helmets for concussive impacts
    The purpose of this research was to examine how four different types of baseball helmets perform for baseball impacts when performance was measured using variables associated with concussion. A helmeted Hybrid III headform was impacted by a baseball, and linear and rotational acceleration as well as maximum principal strain were measured for each impact condition. The method was successful in distinguishing differences in design characteristics between the baseball helmets. The results indicated that there is a high risk of concussive injury from being hit by a ball regardless of helmet worn.
      348Scopus© Citations 7