Search results for: C. Karton

Authors: Ella Bowles, Alexandra Hughes, Clara Karton, T. Blaine Hoshizaki

Abstract:

As a fast-paced and physical game, body contact is an inevitable component in professional men's ice hockey. Despite efforts and advancements in material engineering to create safer equipment, brain trauma continues to persist and burden hockey players. Head and body contact occur in many ways and vary in terms of impact characteristics including the inbound velocity, force, direction, location, and compliance of the surfaces, which in turn influence head dynamics and brain injury outcomes including concussions. It has been reported that glass and board impacts account for approximately 40% of diagnosed concussions. This type of impact often involves the body (i.e., shoulder) contacting the surface prior to head contact, which may influence the head’s dynamic response by interrupting the head’s initial trajectory.  However, the effect of body-first contact during head impacts is not well understood. The purpose of this research is to compare the head’s kinematic response during direct and non-direct (body-first) head-to-glass impacts representative of ice hockey events. Analysis was performed under varying impact conditions of neck stiffness and impact velocity as they have been shown to influence the resulting head dynamics. Data was collected by video analysis of the 2016-17 NHL season and event reconstructions were performed using a Hybrid III headform, an unbiased neck with tension springs (uONSA), and a high-speed impactor. Direct and non-direct impacts were analyzed at three common velocities (3.0, 5.0, 7.0 m/s), and three neck stiffnesses representing low (25%), medium (75%), and high (100%) contraction. Reconstructions representing non-direct head-to-glass impacts used a shoulder bumper as the first point of contact followed by the head’s contact with the glass. The same method and equipment were used to replicate the direct head impacts, where the head made initial contact with the glass. The dynamic response of the head, specifically the peak resultant linear and rotational acceleration, was collected for each impact and compared between direct and non-direct contact under each condition. The results show that non-direct impacts created an initial head acceleration resulting from shoulder contact, preceding a secondary acceleration response from head contact with the glass. Compared to direct head impacts, non-direct impacts consistently resulted in lower linear and rotational acceleration of the head under all neck stiffness and velocity conditions with an average decrease of 32.56 g and 689.33 rad/s2. However, the linear acceleration produced from shoulder contact in non-direct impacts resulted in a higher response compared to direct impacts with low neck stiffness at 5 m/s (55.2g and 41.2g, respectively) and 7 m/s (76.1g and 73.4g, respectively), and medium neck stiffness at 5 m/s (55.4g and 43.9g, respectively ) and 7 m/s (94.4g and 69.5g, respectively. These findings show that non-direct impacts produce complex scenarios that are further influenced by interaction with neck stiffness and velocity. This research provides an understanding of the fundamentals of body-first impacts. With this basis, an understanding of the implications of body-first head-impacts to better distinguish trauma based on events, and adapt protocols, evaluations, technologies, and equipment accordingly.

Keywords: body-first, concussion, direct, hockey, kinematics

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Authors: K. Gilliland, T. Hoshizaki, A. C. T. Laing, C. Karton, T. B. Hoshizaki

Abstract:

A body-first fall is described as a fall where the head is not the first point of contact with the ground or surface. Body-first backward falls are a common cause of head trauma in daily life and sports, leading to injuries ranging from concussions to severe traumatic brain injuries. These falls result in rotational forces during head impact, a significant contributor to brain injury. However, current research on these falls predominantly focuses on direct impacts, limiting our understanding of body-first impacts on head-impact kinematics. Recent research identified that neck muscle stiffness during a body-first fall may significantly influence head impact kinematics and, consequently, the risk of brain injury. This research investigates the influence of neck stiffness on head impact kinematics during body-first backward falls, specifically examining whether neck stiffness affects peak rotational acceleration and, therefore, the risk of brain injury. This research used a 95th percentile Hybrid III (HIII) male headform mounted on an unbiased neck form within the uOttawa neck spring apparatus (UONSA). The unbiased neck form allows for free rotation in all planes. The UONSA was designed to simulate muscle activation by setting the tension in its springs to represent different levels of muscle contraction. There are three muscle groups represented by springs on the UONSA: upper trapezius, splenius capitis, and sternocleidomastoid muscle groups. Two impact velocities (3.5 m/s, 5.0 m/s) and two neck muscle stiffnesses (low, high) were investigated. The low (25%) and high (100%) maximal voluntary contraction forces were used to represent the neck stiffness by adjusting the spring stiffness in the UONSA. A 6.5 cm vertical offset was used to represent the average distance between the back and the back of the head in adult males for the body-first falls. The head form impacted a flat MEP anvil. The back impacted a piece of foam which had a 30% compliance with a 250-newton load to represent the compliance of the back. The dependent variables included peak resultant linear acceleration and peak resultant rotational acceleration, obtained using a 3-2-2-2 accelerometer array with an HIII headform. Peak resultant linear acceleration increased by approximately 60 g with each increase in impact velocity. The highest peak resultant rotational acceleration (22596 rad/s2(±377.86)) is reported for the highest velocity and highest neck stiffness in a body-first fall. In body-first rear impacts, high muscle tension resulted in a disproportionate increase in rotational acceleration, therefore increasing the risk of brain injury. Future research will focus on describing the relationship between neck muscle strength, impact velocity, and head impact kinematics for body first falls. The position of the neck and head before the back impact will be further investigated. This research aims to contribute to a better understanding of the biomechanics of body-first backward falls and inform the development of safer protective equipment, effective training programs for athletes to prevent injury, and more accurate reconstructions of body-first falls.

Keywords: body-first, concussion, head trauma, direct, kinematics, neck stiffness, biomechanics, rotational acceleration

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