A topic I'd like to discuss has come up in the media a lot over the past few weeks; new helmets that are meant to stop or limit concussions and claiming to do so.
There is general agreement among the medical community that concussion incidence can be reduced through rule changes in play, changes in concussion protocol and procedures, and teaching proper hitting and tackling techniques. However, there remains debate as to whether the design of helmets can also help reduce the incidence of concussions.
This is an issue that Deadspin covered very well when the NFL announced a $60 million partnership with GE and Under Armour to "tackle concussion-safety science," of which $10 million would be dedicated to developing "improved helmet technology." When you consider the NFL only spent $60 million (or 0.6% of the NFL's annual revenue) over a 5-year partnership, it's extremely disappointing, especially when 1/6 of the money will go to something [helmets] that may not help reduce concussions at all. It comes into question how much the NFL really cares about the long-term safety and health of it's current players.
The issue regarding helmets arose again (and was once again covered by Deadspin well) when researchers at Virginia Tech released that they would be looking to rate and design new hockey helmets to reduce concussion risk.
To understand why improving helmets wouldn't help reduce concussion risk, it's important to understand the mechanism behind the injury:
UNDERSTANDING CONCUSSIONS - HOW ARE THEY CAUSED?
Also know as a mild traumatic brain injury (mTBI), the concussion is the most common type of traumatic brain injury. Concussion experts have been working together to develop consensus-based principles to establish a consensus definition of what occurs during a mTBI, what a diagnosis entails, and encourage correct return to play (RTP) decisions. The Concussion in Sport Group defined a concussion as:
Concussion is a brain injury and is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. Several common features that incorporate clinical, pathologic and biomechanical injury constructs that may be utilised in defining the nature of a concussive head injury include:
In essence, the panel wanted to define concussion as an injury to the brain which creates a temporary loss in normal functioning. This injury is created by a force and may result in a variety of physical, cognitive and emotional symptoms which differ on a case-by-case basis.
- Concussion may be caused either by a direct blow to the head, face, beck or elsewhere on the body with an "impulsive" force transmitted to the head.
- Concussion typically results in the rapid onset of short-lived impairment of neurological function that resolves spontaneously. However, in some cases, symptoms and signs may evolve over a number of minutes to hours.
- Concussion may result in neuropathological changes but the acute clinical symptoms largely reflect a functional disturbance rather than a structural injury and, as such, no abnormality is seen on standard structural neuroimaging studies.
- Concussion results in a graded set of clinical symptoms that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course. However, it is important to note that in some cases symptoms may be prolonged.
Something I'd like to highlight in this definition (which was put together at the 4th International Conference on Concussion in Sport and included 39 concussion experts) is that concussion isn't just a basic injury, it's a process. This is extremely important especially when recognizing that the onset of symptoms may occurs up to 24 hours after the original hit or injury and they may progress over time. Additionally, the panel agrees that contact with other parts of the body may result in a concussion, you do not need to be hit directly on the head.
This is something that was highlighted by neurologists and concussion experts at Weill Cornell Medical College as well. In an article following the World Cup, Dr. Barry Kosofsky, a pediatric neurologist and concussion expert described the injury process with a nice metaphor:
"The brain can be thought of as resembling a piece of broccoli, with the stalk (brain stem) at the base and the flower (cortex) on top. When someone experiences rotational torque resulting from a concussion, it is similar to stretching the part of the broccoli where the stalk meets the flower. The stalk is held in place but the brain is free to move, due to acceleration or de-acceleration. Concussions are not just due to direct hits, but also the stretching of these fibers due to torque."The article continues with:
While impact and torque cause the initial injury, the physical symptoms of a concussion occur from the resulting neurometabolic cascade in the brain. This cascade causes cellular damage that inhibits neurons' ability to communicate with each other. The result is often impaired cognitive function and the mental fog experienced by athletes after a head injury.PREVENTING CONCUSSIONS - WHAT'S THE DEAL WITH HELMETS?
Helmets are designed to prevent and reduce skull fractures. Their basic design is one that is meant to lessen the blow by spreading the force of impact over a greater surface area. Helmets are designed to attenuate high-impact linear acceleration forces (front-to-back) but do not consider rotational acceleration, despite the strong evidence linking it to injury.
Is it possible to design a helmet that could limit this? No, probably not. Your brain floats in the skull and is cushioned by a thin layer of cerebrospinal fluid. When the brain accelerations or deaccelerates due to a force (be it a hit to the head or neck) the brain can come crashing into the skull or suffer rotational damage. How could an outer shell limit this? The key in preventing concussions is not how hard the head is struck, but how the brain moves inside the skull due to impact.
As the present moment, a concussion is a clinical diagnosis based largely on the observed injury mechanism and symptoms. While this is mostly due to the debated nature of the onset of injury, most of the public believe a concussion will only occur after a huge hit. In reality, it's important that team trainers, coaches and physicians be vigilant of players receiving a large amount of smaller hits or getting into contact and receiving multiple hits in a short period of time. A recent study evaluated the relationship between the force of impact and clinical outcome, finding that magnitude of impact did not correlate with clinical injury (Guskiewicz et al.). The study showed that despite the fact that the impact magnitude of the hits sustained by concussed athletes ranged from 60.5 to 168.7 g, no significant relationships between those impacts and symptom severity/neurocognitive functioning were found. Also, several players sustained hits at that impact threshold and were not diagnosed with concussions.
Bringing it back to helmets, once again, I'll refer to the Conference panel:
There is no good clinical evidence that currently available protective equipment will prevent concussion, although mouth-guards have a definite role in preventing dental and orofacial injury. Biomechanical studies have shown a reduction in impact forces to the brain with the use of head gear and helmets, but these findings have not been translated to show a reduction in concussion incidence.This is echoed in a 2013 report on youth sports-related concussion by the Institute of Medicine and National Research Council which stated "There is limited evidence that current helmet designs reduce the risk of sports-related concussion."
A study done by the Cleveland Clinic compared newer NFL "concussion reduction technology" helmets along with other NFL-approved helmets with vintage "leatherhead" helmets used in the 1940s. Researchers wanted to know how the newer helmets compared in impact testing (which they of course excelled) but also in rotational acceleration. The study found that "in many instances the head impact doses and head-injury risks while wearing vintage leatherheads were comparable to or better than htose while wearing widely used 21st-century helmets." None of the helmets were protecting what causes a concussion, the brain moving inside the skull.
Micky Collins, director of the UPMC Sports Medicine Concussion Program, went on to comment that "there's no helmet out there that will ever prevent a concussion from happening. The main focus should be treating athletes as soon as the symptoms appear."
Even Dr. Henry Feur, member of the NFL's Head, Neck and Spine Committee echoed these statements saying “It’s always some new material. We’ve heard it for years. Reducing the G-forces in a collision may help with concussions, but it has yet to be proven. The problem is that the brain is encased in fluid, and in cases of rotational force, there is little you can do to stop the brain from crashing against the skull.”
There's a multitude of studies published about concussions, helmets, mechanism of injury and rates of sports-related concussion. I won't list them all here as most of them all agree that incidence of concussion is similar regardless of the helmet brand or what the helmet is selling.
Some studies may state that use of sport-specific helmets have been found to reduce head injuries such as concussions. However, these case studies have a hard time eliminating confounding factors such as:
- Risk-avoidant behavior leading to less injury rather than the helmet itself
- Concussions that aren't diagnosed
- The use of protective equipment adversely affecting player behavior, encouraging risky hits.
The problem is, parents and players are eating up the marketing for these "Five-Star" and "Concussion-reducing technology" helmets. Sales for five-star football helmets which run upwards of $250 have soared in the last year, while older helmets have plunged. This is about money right now.
The research being done at Virginia Tech and other institutions is not a bad thing. If they can somehow find a way to decrease rotational acceleration inside the skull via an outer-shell, it would be ground-breaking. It is, however, extremely unlikely.
Bartsch A, Benzel E, Miele V and Prakash V. Impact test comparisons of 20th and 21st century American Football Helmets. J Neurosurg 116:222-233, 2012. Published online November 4, 2011; DOI:10.3171/2011.9.JNS111059.
McCrory P, et al. Br J Sports Med 2013;47:250-258.
McCrory P, et al. Br J Sports Med 2013;47:268-271.
Guskiewicz KM, Mihalik JP, Shankar V, et al. Measurement of head impacts in collegiate football players: relationship between head impact biomechanics and acute clinical outcome after concussion. Neurosurgery 2007;61:1244–52.
Institute of Medicine and National Research Council. Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. Washington, DC: The National Academies Press, 2014.