By now, the stomach-churning footage of Max Pacioretty of the Montreal Canadiens slamming headfirst into a post during an NHL game on March 8 is well-known. The hit, delivered by Zdeno Chara of the Boston Bruins, happened in less than a second, but it took several unnerving minutes for medical personnel and teammates to carry an unconscious Pacioretty off the ice. Doctors later diagnosed him with a concussion and a fractured vertebra, from which he is still recovering. Considering the powerful collision, it’s stunning that the 22-year-old wasn’t hurt worse or even killed, as many fans and players feared that night.
But to truly marvel at the dangerous blow that Pacioretty survived, one must watch a precise five-second black and white video just created by scientists at the University of Ottawa. Led by Blaine Hoshizaki, director of the elite Neurotrauma Impact Science Laboratory, researchers have reconstructed a hit similar to the Pacioretty-Chara one. The footage shows a dummy head wearing a helmet similar to the one Pacioretty uses. A metal rod covered in two-inch foam mimics the padded stanchion that Pacioretty struck. An air compressor unleashes the rod on the head form, which is pummelled at the exact same speed and location as when Pacioretty rammed into the post. The impact launches the dummy into a sideways extension—the neck stretches until it’s perpendicular to the rod, before the head form snaps back and slightly rotates.
Witnessing the hit recreated in the isolation of a lab makes it all the more disturbing to watch. But for Hoshizaki, the goal is scientific. His team is determined to understand the relationship between brain injuries such as concussions, helmet performance, and the risky hits that hockey players give and take during a game—and to find out whether equipment should be improved or whether certain hits should be banned in the future.
The Pacioretty-Chara reconstruction confirms that hockey helmets excel at preventing catastrophic brain injuries such as skull fractures and subdural hematomas, which are caused by “linear acceleration” (which happens when players fall and hit the ice or receive an impact directly through their centre of mass). On the other hand, it also demonstrates that helmets are not built to prevent mild traumatic brain injuries such as concussions, which are caused primarily by “angular acceleration” (a rotational impact such as when a boxer throws a hook punch to the side of an opponent’s head).
What’s more, this reconstruction explains why Pacioretty will probably recover from his concussion faster than superstar Sidney Crosby of the Pittsburgh Penguins, who has been sidelined since Jan. 5. As Maclean’s recently reported, Hoshizaki’s team has reconstructed the first of two hits to the head that preceded Crosby’s concussion diagnosis. That hit occurred on New Year’s Day, when David Steckel (then of the Washington Capitals, now playing for the New Jersey Devils) collided with Crosby—shoulder to the left side of the head—and sent him flipping through the air and crashing onto the ice.
By comparing the two reconstructions, especially the 3-D brain models generated by sensors inside the dummy, Hoshizaki’s team can see the different risk of brain tissue damage each player might have experienced. The results are as fascinating as they are perplexing: the brain model from the Crosby reconstruction shows a rainbow of tissue stress, while the brain model from the Pacioretty reconstruction is mostly blue, representing less risk of tissue damage.
Hoshizaki suggests that although the Pacioretty-Chara hit happened at a higher speed than the Crosby-Steckel one (36 km/h versus 27 km/h), and even though Pacioretty was knocked out, the angular acceleration lasted longer in the case of Crosby than Pacioretty (20 milliseconds compared to seven milliseconds, respectively). Since angular acceleration is so closely connected to the risk of concussion, that might explain why the brain model generated by the Crosby-Steckel reconstruction indicates so much more tissue stress. As well, the researchers hypothesize that the location of the impact on each player’s head may explain why the tissue damage varies. Hoshizaki says that the front of the brain, such as where Pacioretty was hit, may be more robust than the sides, which is where Crosby was struck.
Going forward, Hoshizaki’s team are working toward mapping which parts of the brain are most vulnerable to hits to the head. Meanwhile, fans await the return of Pacioretty and Crosby—whenever that might be.