Documentation:FIB book/Helmet Use In Hockey Collisions

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Abstract

Amongst the hockey community, concussions are a hot topic in injury research due to the increasing prevalence in youth and professional athletes[1][2]. As technology and level of competition improve, so do the speed and severity of hockey collisions. Existing mechanisms for concussion prevention - helmets and mouthguards - are extremely useful in preventing concussion due to various collisions: reducing severe head injury by up to 28%[3]. With that being said, technological innovation and policy changes seem to lag behind the increased severity of collisions. Furthermore, innovation is severely hindered due to the lack of clear biomarkers for concussion and the lack of development of comparable testing procedures to test protection mechanisms. Given the lag in innovation and technology, combined with the clear importance of helmets in mitigating the severity of concussions, investigations must be completed to understand how the model of a helmet and how that helmet fits may affect concussion rate and severity.

Background

Epidemiology

Concussions are one of the most common injuries in hockey players, accounting for 10% of injuries at a professional level and up to 66% of injuries in youth 13-18 years old[4][5]. At the professional level, a concussion results in a time loss of roughly six days (defined by six days away from competition), with time loss increasing by 2.25x for every subsequent concussion[6]. Meanwhile, in youth, this time loss is significantly greater, translating to at least 10 days for 74% of concussions, and at least 30 days for 20% of concussions[7]. Likelihood of concussion also increases with every additional concussion sustained[6]. Symptoms of concussion, which significantly vary depending on injury severity and the patient (adult female patients are more likely to express symptoms than their male counterparts) can cause physical (e.g. headaches) or mental (e.g. irritability, sleep challenges) changes in the individual[8][9]. Recovery techniques are largely based on avoidance of physical and mentally taxing activities (e.g. reading, playing video games) for at least 48 hours following injury[8]. There are currently no approved clinical techniques for treating concussions.

Mechanism of Injury - Concussions

Figure 1 - Skull stress and brain strain following linear and realistic impacts. Linear impacts do not typically result in concussion

Post-mortem analysis of individuals in impact sports alongside imaging techniques of brain mechanics has elucidated how concussions occur. Overall, the main cause of concussion is inertial loading during impact where, upon impact, the brain is still in motion and must rapidly decelerate inside the skull[10]. Both linear and rotational acceleration occur in nearly every instance of concussion[10]. Impact direction has significant implications on the production of concussion. Linear impact leads to relatively linear impacts, resulting primarily in skull fracture (figure 1). Realistic impacts in hockey, for example, are not linear and rather produce rotational acceleration upon impact, resulting in concussion. Past research has focused only on linear acceleration and have unrealistically translated the results to real-world impacts. Recent research has realized the significance of rotational acceleration due to the higher sensitivity of brain tissue to shear forces[10]. On the cellular level, shear forces can stretch or tear axons, triggering ionic imbalances or excessive neurotransmitter release. This dysfunction can disrupt neural pathways and cause a reduction in blood flow, making cells more vulnerable to secondary injury during recovery[11].

Long-Term Consequences - CTE

Concussions produce short-term pain, but may have long-term consequences. Multiple concussions early in life can affect the risk of developing a neurodegenerative disease - such as Alzheimer’s Disease (AD) or Parkinson’s Disease - later on[10]. For instance, just one concussion may increase the risk of dementia by 22-26%[12]. Also, as more concussions take place in a patient the severity of the symptoms and physiological results as well as the vulnerability to further concussions increases[13]. Most notably, repeated concussion often leads to CTE - a progressive brain disease that leads to severe cognitive and behavioural impairments[14]. CTE has many similarities to AD including on the molecular level, showing an abnormal accumulation of Tau protein[14]. Tau accumulation can cause inflammation in the brain and lead to neuronal death, resulting in symptoms such as memory loss, tremors, impaired judgement and personality changes[14].

Current Prevention Techniques

Preventing concussion is the first line of defence against the injury. Protective equipment (helmets, mouthguards), education around how to properly use the protective equipment (Hockey Canada Concussion Education and Awareness Program, regular helmet checks), avoidance procedures (rules preventing contact), and physical training (neck muscle training) are commonly used for injury prevention[15][16]. Rule changes in youth hockey implemented in the last 20 years have reduced intentional collisions, particularly those to the head, and rules have been applied making the use of mouthguards and helmets compulsory for all age groups[17][18][19]. Helmets function to reduce the severity of the concussion through mechanisms such as force distribution, energy absorption, deceleration management, protection against translational forces, and reduction of peak impact[20] [21]. In Canada, helmets used in the competitive setting are required to be currently approved by the Canadian Standards Association (CSA) under CSA Standard Z262.1 which outlines thresholds for third parties to verify the safety of their helmets[20]. Notably, this document does not include any standards around rotational acceleration despite research increasingly showing the importance of rotational acceleration in concussions[10][19]. Further issues lie in the fact that there are currently no reliable surrogate models for concussion, and overall, the validity of CSA Standard Z262.1 comes into question.

Past Work - Helmet Designs and Fit

Hockey helmets are designed to cover the heads of players and cushion them against head injuries[20]. Standard helmets consist of foam liners, gel liners, and air bladder systems inside the hard outer helmet - all of which have unique impact mechanics[20]. It is found that polyethylene foam liners have better capacity to absorb falls from greater heights (i.e. better energy absorption and force dissipation abilities) and gel liners provide a more customized fit and better shock absorption compared to air bladder systems, which are less equipped to uniformly reduce concussion severity[20]. In addition, foam or gel-lined helmets are found to better reduce symptoms such as light and noise sensitivity and allow for shorter duration of symptoms compared to air bladder helmets[21]. Overall, the composition of the helmet liner is critical for the extent of protection the helmet as a whole provides and therefore could be implicated in concussion frequency rates (although current tests do not account for rotational forces)[10]. However, the performance of such helmet liners could vary with specific impact conditions, emphasizing the need for further research[21].

In terms of thickness of padding in helmets, there is some debate in the literature. 2006 and 2014 studies examining football helmets found that concussion risk was reduced substantially when there was thicker padding over the zygoma and mandible region[22][23]. In contrast, subsequent studies found either no difference or increase in concussion incidence rate for the thicker design[24]. Further testing on the impact of padding thickness and the prevalence of concussion should be completed to understand their relationship.

Figure 2 - a) Ring Fit Dial helmet b) Test line on the Bell Adrenaline (T1) helmet

One study focusing on different bike helmet models has suggested that because it should not be assumed that helmets provide adequate protection in all areas, the effectiveness of helmets could be improved with protection in a wider range of impact locations[25]. In this study, a mix of what they call “traditional style” helmets and BMX style helmets (hard shell with limited ventilation) with expanded polystyrene (EPS) liners were tested. It was found that only one of the helmets limits peak acceleration below the limit they specify[25]. The paper also finds that retention systems (Figure 2a) in helmets (i.e. chin straps or fitting systems) in helmets can be dangerous because to create room for these EPS gets removed for hardware, the system can allow for excessive helmet rotation, retention straps can be attached by rivets that can protrude towards head during collision and hard plastic used in some adjustment dials can be damaging[25]. As a result the paper goes on to suggest that helmets with a lower test line meaning they have greater coverage of head (Figure 2b), and helmets with carefully designed retention systems could be better at preventing concussion[25].

Helmet fit is another important research area in determining how helmets can be most effective in lowering concussion incidence and severity. In a large study with 4580 youth football players, poorly fitting helmets were found to be associated with worsened symptoms (drowsiness, hyperexcitability, sensitivity to light, etc.) as well prolonged symptom duration following concussion[26]. Researchers revealed that an improperly fitting helmet may act separately, and not as a unit alongside cervical muscles, diminishing the ability of the system to absorb rotational forces which are critical in concussion avoidance[26]. The study notes that at least 7% of helmets worn by athletes who suffered “catastrophic intracranial injuries” were defective or improperly fitted[26]. A 2021 study focusing on youth hockey compared concussed and non-concussed players (matched by age, sex and competition level) and concluded that improper helmet fit was a significant predictor of concussion risk[27]. Helmet fit was assessed in terms of eye coverage, tightening of the chin strap, positioning of the helmet crown with respect to the eyebrows and more[27]. The paper also found that the majority of athletes incorrectly believed that their helmets were fitted properly indicating that improvements in education and objective assessments of helmet fit are necessary[27]. These findings illustrate the importance of educational implementations and regular “helmet checks” before competition - in which referees or other officials ensure all players have their helmets properly sized and secured.

Limitations and Future Directions

There are several limitations of current work around different helmet models and fit, and the rate and severity of concussions associated with them, and as a result many future directions in this area. First, despite widespread acknowledgement in the literature that rotational acceleration is the most important cause of concussions, current testing procedures - including in the studies discussed in this review - prioritize linear acceleration[10]. Future research must focus on the development of tests that consider both rotational and linear forces, and the production of helmets that are better at mitigating these forces. One relatively new technology in helmet design, called multi-directional impact direction system (MIPS), adds a low friction layer between the shell and padding layers of the helmet to allow the helmet to slide during impact, lowering the rotational forces transmitted to the head[28]. Unfortunately, MIPS has not been widely integrated into all models of hockey helmets[28]. Future work to integrate this breakthrough system into all helmet models, for both children or youth and adults of all levels of hockey would be highly beneficial.

Next, as evidenced in this review, there is very little sport-specific research into what helmet types or fits might be the safest in each sport. Different sports have different impact forces, directions and types, therefore research should be separated in a sport-specific manner. For example, loading direction and quantity are very different in a cycling accident compared to a hit in hockey. Therefore the inter-sport translation of information is poor, yet still frequently occurs. Similarly, there is seemingly less research around helmet models and fit in adults relative to research in this area around children. Given the range of anatomy and experience of youth compared to adult athletes, it will be necessary to investigate the influence of helmet fit on concussion risk in adults.

As discussed, helmet fit is a key aspect of helmet effectiveness, but achieving and maintaining proper fit is difficult, owing to many factors like sweat, rain, hairstyle, and what one wears underneath the helmet[26]. Better criteria and education around proper helmet fit and more objective means of evaluating fit, such as through wearable sensors, should be the focus of future studies. Future research could also explore new technologies, such as 3D scanning and printing, to create custom-fit helmets that are more protective and fit better. These technologies have the potential to transform helmet design and protect athletes in contact sports.

Lastly, it is unclear how the quantity and severity of concussions are most likely to cause CTE. Elucidating this is imperative in designing helmet systems to not only reduce the immediate impact of the concussion but also reduce an individual’s risk for long-term effects such as CTE[14].

References

  1. ↑ A. S. D. Gamble et al., “Helmet Fit Assessment and Concussion Risk in Youth Ice Hockey Players: A Nested Case-Control Study,” Journal of Athletic Training, vol. 56, no. 8, pp. 845–850, Nov. 2020, doi: https://doi.org/10.4085/1062-6050-0294.20.
  2. ↑ A. W. Kuhn and G. S. Solomon, “Concussion in the National Hockey League: a systematic review of the literature,” Concussion, vol. 1, no. 1, Mar. 2016, doi: https://doi.org/10.2217/cnc.15.1.
  3. ↑ D. A. Chisholm et al., “Mouthguard use in youth ice hockey and the risk of concussion: nested case–control study of 315 cases,” British Journal of Sports Medicine, Jan. 2020, doi: https://doi.org/10.1136/bjsports-2019-101011.
  4. ↑ M. Tuominen, M. J. Stuart, M. Aubry, P. Kannus, and J. Parkkari, “Injuries in men’s international ice hockey: a 7-year study of the International Ice Hockey Federation Adult World Championship Tournaments and Olympic Winter Games,” British Journal of Sports Medicine, vol. 49, no. 1, pp. 30–36, Oct. 2014, doi: https://doi.org/10.1136/bjsports-2014-093688.
  5. ↑ P. H. Eliason et al., “Safe2Play in youth ice hockey: injury profile and risk factors in a 5-year Canadian longitudinal cohort study,” Annals of Medicine, vol. 56, no. 1, Aug. 2024, doi: https://doi.org/10.1080/07853890.2024.2385024.
  6. ↑ 6.0 6.1 B. W. Benson, W. H. Meeuwisse, J. Rizos, J. Kang, and C. J. Burke, “A prospective study of concussions among National Hockey League players during regular season games: the NHL-NHLPA Concussion Program,” Canadian Medical Association Journal, vol. 183, no. 8, pp. 905–911, Apr. 2011, doi: https://doi.org/10.1503/cmaj.092190.
  7. ↑ K. J. Schneider et al., “Concussion rates and recovery in elite youth ice hockey players,” British Journal of Sports Medicine, vol. 51, no. 11, pp. A39.3-A40, May 2017, doi: https://doi.org/10.1136/bjsports-2016-097270.101.
  8. ↑ 8.0 8.1 “Concussion: Symptoms and treatment - Canada.ca,” Canada.ca, 2019. https://www.canada.ca/en/public-health/services/diseases/concussion-sign-symptoms.html
  9. ↑ S. J. Preiss-Farzanegan, B. Chapman, T. M. Wong, J. Wu, and J. J. Bazarian, “The Relationship Between Gender and Postconcussion Symptoms After Sport-Related Mild Traumatic Brain Injury,” PM&R, vol. 1, no. 3, pp. 245–253, Mar. 2009, doi: https://doi.org/10.1016/j.pmrj.2009.01.011.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 D. F. Meaney and D. H. Smith, “Biomechanics of Concussion,” Clinics in Sports Medicine, vol. 30, no. 1, pp. 19–31, Jan. 2011, doi: https://doi.org/10.1016/j.csm.2010.08.009.
  11. ↑ M. Collins, “Concussion Definition and Pathophysiology The Evolving Definition of Concussion Regarding Cerebral Concussion…… Pathophysiology of Concussions,” 2006. Available: https://dhhs.ne.gov/ConcussionManage/Documents/ConcussionDefnPathophysiology.pdf
  12. ↑ The University of Queensland, “How long does concussion last: long-term effects,” Uq.edu.au, Aug. 16, 2018.  https://qbi.uq.edu.au/concussion/how-long-does-concussion-last-long-term-effects
  13. ↑ Committee on Sports-Related Concussions in Youth; Board on Children, Youth, and Families; Institute of Medicine; National Research Council; Graham R, Rivara FP, Ford MA, et al., editors. Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. Washington (DC): National Academies Press (US); 2014 Feb 4. 5, Consequences of Repetitive Head Impacts and Multiple Concussions. Available from: https://www.ncbi.nlm.nih.gov/books/NBK185336/
  14. ↑ 14.0 14.1 14.2 14.3 “Chronic Traumatic Encephalopathy (CTE)?,” Uq.edu.au, Oct. 23, 2024. https://qbi.uq.edu.au/brain/brain-injury/concussion/chronic-traumatic-encephalopathy-cte
  15. ↑ N. A. Shlobin, K. Goel, J.-S. Chen, and D. Kondziolka, “Concussions in ice hockey: mixed methods study including assessment of concussions on games missed and cap hit among National Hockey League players, systematic review, and concussion protocol analysis,” Neurosurgical Focus, vol. 57, no. 1, p. E11, Jul. 2024, doi: https://doi.org/10.3171/2024.4.focus24103.
  16. ↑ C. L. Collins et al., “Neck Strength: A Protective Factor Reducing Risk for Concussion in High School Sports,” The Journal of Primary Prevention, vol. 35, no. 5, pp. 309–319, Jun. 2014, doi: https://doi.org/10.1007/s10935-014-0355-2.
  17. ↑ “Hockey Canada’s New Head Contact Rule,” Hockeycanada.ca, 2021. https://www.hockeycanada.ca/en-ca/news/2011-gn-018-en
  18. ↑ “Hockey Canada Announces Ban on Body-Checking in PeeWee Hockey - SportMedBC,” SportMed BC, Jun. 2013. https://sportmedbc.com/hockey-canada-announces-ban-on-body-checking-in-peewee-hockey/
  19. ↑ 19.0 19.1 Champoux, L. (2021) A comparison of three rotational ice hockey helmet test protocols, Recherche uO Research Home. Available at: https://ruor.uottawa.ca/items/d11e5783-5de8-4738-ae7e-fe7954abf820
  20. ↑ 20.0 20.1 20.2 20.3 20.4 “Rule 3.6 – Protective Equipment» Rule Book Admin,” rulebook.hockeycanada.ca. http://rulebook.hockeycanada.ca/english/part-i-technical-rules/section-3/rule-3-6/
  21. ↑ 21.0 21.1 21.2 The University of Queensland, “Do helmets protect against concussion?,” Uq.edu.au, Jun. 06, 2018. https://qbi.uq.edu.au/concussion/do-helmets-protect-against-concussion
  22. ↑ Collins M, Lovell MR, Iverson GL, Ide T, Maroon J. Examining concussion rates and return to play in high school football players wearing newer helmet technology: a three-year prospective cohort study. Neurosurgery. 2006 Feb;58(2):275-86; discussion 275-86. doi: https://doi.org/10.1227/01.neu.0000200441.92742.46. PMID: 16462481..
  23. ↑ Sariaslan A, Sharp DJ, D’Onofrio BM, Larsson H, Fazel S (2016) Long-Term Outcomes Associated with Traumatic Brain Injury in Childhood and Adolescence: A Nationwide Swedish Cohort Study of a Wide Range of Medical and Social Outcomes. PLoS Med 13(8): e1002103 https://journals.plos.org/plosmedicine/article/file?id=10.1371/journal.pmed.1002103&type=printable
  24. ↑ Emery, C.A. et al. (2017) What strategies can be used to effectively reduce the risk of concussion in sport? A systematic review, British Journal of Sports Medicine. Available at: https://bjsm.bmj.com/content/51/12/978
  25. ↑ 25.0 25.1 25.2 25.3 DeMarco AL, Chimich DD, Bonin SJ, Siegmund GP. Impact Performance of Certified Bicycle Helmets Below, On and Above the Test Line. Ann Biomed Eng. 2020 Jan;48(1):58-67. doi: 10.1007/s10439-019-02422-x. https://pubmed.ncbi.nlm.nih.gov/31768795/ Epub 2019 Nov 25. PMID: 31768795.
  26. ↑ 26.0 26.1 26.2 26.3 D. A. Greenhill, P. Navo, H. Zhao, J. Torg, R. D. Comstock, and B. P. Boden, “Inadequate Helmet Fit Increases Concussion Severity in American High School Football Players,” Sports Health: A Multidisciplinary Approach, vol. 8, no. 3, pp. 238–243, Mar. 2016, doi: https://doi.org/10.1177/1941738116639027.
  27. ↑ 27.0 27.1 27.2 A. S. D. Gamble et al., “Helmet Fit Assessment and Concussion Risk in Youth Ice Hockey Players: A Nested Case-Control Study,” Journal of Athletic Training, vol. 56, no. 8, pp. 845–850, Nov. 2020, doi: https://doi.org/10.4085/1062-6050-0294.20.
  28. ↑ 28.0 28.1 Wang, C. (2023) Mips Helmet Technology Mimics the Meninges, Request rejected. Available at: https://www.mcgill.ca/oss/article/medical-technology/mips-helmet-technology-mimics-meninges
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