Rob Lynall was working as an athletic trainer when he started noticing that his athletes returning to the field after recovering from a concussion were suffering more lower body injuries like ACL tears and ankle sprains than other players. They tested normally on all the measures of concussion recovery, but they kept coming back a few months later with other problems.
"I didn't have any data, that was just our experience," says Lynall, who's now a professor at the University of Georgia. But when he started doing concussion research a few years later, he focused in on the relationship between concussion and injury risk—and in December 2015, he published a study in the journal Medicine & Science in Sports & Exercise that backed his anecdotal observation up with real data: For up to a year, he found that athletes who had a concussion were twice as likely to have a lower body injury as athletes who did not.
More research is piling up to back up the anecdotal evidence. Daniel Herman, professor of sports medicine presented data on injury risk at the American Society for Sports Medicine conference in 2013, and published a paper with those results in August 2016. Researchers from the University of Wisconsin and the University of Delaware reached similar conclusions.
Now, researchers are drawing connections between these findings and past research on changes a concussion causes to balance and movement. Those changes linger long after other symptoms of a concussion have gone away, and may contribute to the noted rate of injury—there's even some indication that they could lead to increased risk of arthritis.
Between 1 and 3 million sports-related concussions occur annually in the United States. There's been new attention to the danger of concussion in the past decade, but most of the conversation around concussions focuses on cognitive symptoms: headaches, difficulty concentrating, memory deficit, and the risk of changes in the brain lingering years down the line. This new line of research adds even more items to the laundry list of problems caused by concussions. It might take a few years, but this research could significantly change the way doctors and trainers test for and treat these injuries. "It just further emphasizes the fact there is so much more we don't know about concussions," Lynall says. "We have to be open to changing the way we manage them."
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Doctors and trainers have long used movement changes to test for concussion—the Standardized Concussion Assessment Tool, a common sideline test for concussions, includes a balance test. But balance resolves quickly after the initial injury. To the naked eye, someone recovering from a concussion seems to be walking and moving normally only a few days later.
More complicated movement tests, though, can pick up more subtle problems. Jessie Oldham, a doctoral student at the University of Delaware, studies gait as the main test of movement impairment. "The static balance tests are not sensitive enough to identify all impairments," she says. Gait tests measure the way people walk and move, and they're a more sensitive indication of how well the neuromuscular system—the network of muscles and nerves critical for movement—is working. "Your brain is controlling all of these movements," says David Howell, professor of orthopedics at the University of Colorado School of Medicine. "It's a fairly complex process and it's something that after a brain injury seems to be altered."
These gait changes are usually too small to pick up just by watching someone walk, Howell says, which is why an athlete, parent or coach wouldn't necessarily find something wrong. But with specialized motion tracking technology, researchers continue to find changes even after other symptoms are gone. Howell's research found that gait changes could linger up to two months after a concussion.
Athletes may be cleared to return to the playing field after scoring normally on a static balance test, says Oldham, but their gait tests could still show abnormalities. "There are huge implications in term of return to play if you're still having motor control impairments," Oldham says.
The theory, Howell says, is that gait and neuromuscular changes lead to increased risk of injury. "There appears to be something that is happening, but we don't know what that mechanism is," he says. According to Herman, the connection makes sense. "We know very well that altered neuromuscular control increases injury risk," he says. "The fact that these athletes are returned to play with subtle but important neuromuscular differences may increase injury risk."
Oldham is hoping to fill in the mechanistic research gap. "We've seen there is some sort of connection, and we want try to link that back to specific gait." She's tracking a group of concussed athletes and looking to see if the ones with significant gait changes are also the ones who get injured. She's also interested in the way changes in gait might connect back to changes in the brain, and is planning to start incorporating brain scans into her research. "We want to see if anything shows up on fMRI in these individuals who are displaying gait impairments," she says.
Other ongoing studies are also trying to home in on the mechanisms involved. Terese Chmielewski, who also worked on one of the recent studies on concussion and injury risk, is doing the final data analysis on a study that looked specifically at muscle activation in the thigh before and after injury. The project also used fMRI to try and identify the particular regions of the brain connected to those muscle activations. "When you go to contract your muscle, you use your motor planning part of the brain," she says, and concussion may interfere in that process.
Up until now, most gait studies have only tracked athletes for a few months after injury. That's frustrating to Lynall, who wants to understand the long-term effects of concussion on the body—especially because his data shows increased injury risk at least up to one year. "We have no idea what comes next," he says. To quell some of that frustration, Lynall looked at the data from Health Survey of Retired National Football League Players, and thought the data on arthritis might have a relationship with gait.
"We know traumatic injuries predispose people to arthritis later in life, and changes in gait due to those injuries can hasten osteoarthritis," Lynall says. "If people have concussion and changes in gait, and it's for prolonged time, maybe it's setting folks up for arthritis."
His analysis, published in June in the Journal of Athletic Trainers, found that those retired NFL players who reported concussion during their careers had higher prevalence of arthritis. Lynall says it's important to be cautious about over-interpreting those results—they're based on people self reporting what they remembered from their careers—but that they leave avenues open for more research. "All we did was raise more questions about what's going on which is good for me, because I'm trying to find answers."
The long term goal with this research is to develop better measures of testing for concussion, better ways of treating them, and better tools to identify when an athlete is ready to return to the field. Translating all of the ongoing research into actual tests doctors and trainers can use, though, won't be easy or cheap.
"A high school or middle school won't have access to these sophisticated lab measures," Oldham says. One of her main goals is to develop a gait test that's accurate and easy to use. Her work focuses on the tandem gait test—it's essentially a heel-to-toe walking test, she says, and all you need is tape and a stopwatch. Compared with a balance test, "we've demonstrated tandem gait is more sensitive and shows more impairment," she adds.
Results from Oldham's research are strong, says Haddow, who has worked with her in the past. But he's reluctant to recommend anything to doctors and trainers until we know the mechanism underlying both gait change and injury. "Until we understand that better, we don't have any means to intervene or understand the effectiveness of this intervention," he says. "But as we understand this better we'll be able to home in on the way we assess the injury and identify dysfunction. Lynall agrees. "We're not at a point where we can say we change the way we manage concussion recovery… We're not anywhere near having this figured out."
But new protocols, or preventative measures could be a hard sell for coaches, parent and athletes, Herman says. "It's definitely a leap to the point that this person is completely fine when it comes to school work and symptoms and a neurological exam, but they're at higher risk for injury. A lot of people would say, 'Okay, I'll take that risk."
Haddow hopes that sound research and clear data would help move that process along. He hopes to be able to give doctors a way to measure potential injury risk, and they'll have to make their decisions based on that information. "As a clinician, they're going to have to decide what is that level of acceptable risk for that patient."
But at the end of the day, Oldham says, the goal is to give concussed players the best care and the most information possible. "We're just trying to make sure we're doing everything we can to look at the athletes from all angles to make sure they're truly recovered."
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