May 2018

Concussion and lower extremity injury

As in adults, youth athletes who sustain a concussion increase their chances of experiencing a lower extremity injury, and the rise in risk can last for at least a year. Researchers are investigating the reasons underlying the connection, as well as trying to answer the crucial question: when is it safe for athletes to return to play?

By Jill R. Dorson

When an athlete gets a concussion, it’s not just his or her brain that is at risk for further injury. Researchers have found that the odds of lower extremity injuries rise, both in the short and long term1 (see “Concussion repercussions: Studies explore lower extremity effects,” LER, June 2016, page TK).

Two clinicians, one based in Colorado, the other in Georgia, have been on the cutting edge of studying the effects of concussion on lower extremity function young athletes. They say this area of research is in its infancy, but so far, the research has shown tangible, applicable results.

David Howell, PhD, ATC, a lead researcher at the Sports Medicine Center at Children’s Hospital in Aurora, CO, and an assistant professor of orthopaedics at the University of Colorado School of Medicine, also in Aurora, has been focused on dual-task gait issues following concussions. In layman’s terms, is it harder to chew gum and walk after you’ve had a concussion?

Across the country, Rob Lynall, PhD, ATC, the codirector of the Concussion Research Lab at the University of Georgia in Athens, and an assistant professor in the university’s Department of Kinesiology, has been studying time-loss injuries following concussions and how long the increased risk of injury lasts. He and his colleagues have written about the link between musculoskeletal issues and concussion in adults for LER (See, “Brains, sprains, and chronic pain,” LER, November 2017, page TK) but much of Lynall’s research is focused on a younger population.

According to a 2003 study2 there were more than 1.5 million traumatic brain injuries in the US that year, and the highest incidence of injury occurred in young children and men.

Lynall’s most recent study,1 published in 2017 in the Journal of Athletic Training, found that 34% of high school athletes who returned to play following a concussion then sustained a lower extremity injury.

Returning to play may be a flashpoint for injury, ie, a concussed athlete is back on the field, but has missed playing time, may be out of shape, and has to reacclimate.

Those findings are similar to those from a study3 in adults commissioned by the US Army Research Institute of Environmental Medicine. The study looked at more than 23,000 soldiers, half whom had suffered concussions and half whom had not, over a two-year period. Results showed that, compared with nonconcussed soldiers, the possibility of a concussed soldier suffering a subsequent lower extremity injury was 45% greater after 15 months and 38% greater after two years.

Lynall’s large-scale pediatric study looked at more than 46,000 injuries sustained by more than 18,000 athletes across 27 sports, and focused on “time-loss” lower extremity injuries, ie, those that caused an athlete to miss at least a day of play or practice. Lynall believes it is the first study to look at time-loss injuries alone, as most research includes both time-loss and non-time-loss injuries.

“I think the most interesting thing between the relationship between concussions and musculoskeletal injuries is that every time someone looks it, they look at it a little differently, but still come to the same conclusions,” Lynall said. “I think that [teasing out time-loss injuries] may be important going forward … if we want to figure out what is driving the relationship.”

The brain-lower extremity link

Howell and Lynall see a clear connection between concussion and lower extremity injuries in youths and adults. What they haven’t uncovered yet is the mechanism that causes this to happen. In fact, Howell was the lead researcher on a dual-gait task study in which Lynall also participated. The study, published in a 2018 issue of the Journal of Neurotrauma4 investigated the ability of concussed youth athletes (average age 17 years, 52 girls) to perform two tasks simultaneously once every 21 days until they were considered recovered. The athletes reported back in a year if they had sustained additional lower extremity injuries.

The results indicated that as the ability to execute dual-task gait exercises worsened, the incidence of time-loss injuries rose significantly—for up to a year.

“I expected to see that there was a high risk at the very beginning and that it would tail off in the coming year,” Howell said. “But that’s not the case. If you cut the time period off at, say, the first ninety days, then you don’t see an association, but if you got further than that, then there is an association. Exposure plays a big part, and as you extend that window out further, that association becomes stronger. We’re trying to understand what mechanisms are responsible for this.”

The results of his study were similar to a systemic review5 published in 2017 that found that concussed youth athletes had less stability while performing a dual task during the first 72 hours after sustaining the concussion.

Lynall had previously investigated this area in a 2015 study6 that compared dynamic activity in concussed and nonconcussed college-aged athletes for one year. He found that concussed athletes were more likely to struggle with dynamic tasks.

“It’s really interesting,” Lynall said. “When we first got into this for our 2015 paper, we thought maybe in the first month, we might have a greater chance of seeing this elevated chance of injury. We broke it out at ninety, one-hundred-twenty, and three-hundred-sixty-five days and saw the increase out to a year.”

There is little data past the one-year mark, he said.

Among the reasons youth athletes may be more likely to sustain injuries later rather than sooner, Howell suggested, is that athletes may have poor motor control for an extended period postconcussion making them more prone to injury. In addition, there are fewer lower extremity injuries immediately following a concussion because athletes aren’t playing or practicing. Lynall also pointed out that getting back to play may also be a flashpoint—ie, a concussed athlete is back on the field of play where he or she has missed playing time, may be out of shape, and has to re-acclimate to the speed of play. All of these factors can put an athlete at risk.

When it comes to studying the relationship between concussions and kids, Lynall is considered the expert. Although the concept that a concussed person is at higher risk for lower extremity injury translates from adults to kids, Lynall has found that getting to the information needed to further study the relationship can be challenging. As with many illnesses or injuries, kids can be tougher to diagnose.

“Largely, you’re looking at the same things you’re looking for in adults—are they slower than normal? Kind of out of it? Foggy? Do they have a glassed-over look to them?” Lynall said. “Children are always the toughest, though they do tend to be honest [about experiencing symptoms, even though it may keep them from returning to play] even though they don’t always know something happened to them.”

Girls are at higher risk

Howell is currently involved in a Boston-based study looking at women and concussions and noted that past studies have shown the “incidence of concussion is more prevalent in girls and women [than in men]. … But to my knowledge, no one has been able to stratify this level so far.”

Among the previous studies showing that females are more prone concussions, a 2009 review7 published in the British Journal of Sports Medicine revealed that nine of 10 included studies showed a higher incidence of concussion in female versus male athletes. A 2015 JAMA Pediatrics study also found that female high school soccer players were about 1.5 times more likely to sustain a concussion than males players.8

Similarly, a review of data9 from 207 athletes collected at a Canadian concussion clinic showed women and girls not only sustained more concussions, but that the injury was often more severe than in their male counterparts and that the female athletes took longer to heal. While 34% of men and boys completed concussion treatment in two months, only 12% of women and girls, with many experiencing concussion related issues up to six months postinjury.9

Women and girls also reported more subjective symptoms, as well as more objective physiological symptoms of concussion, such as vision issues and trouble maintaining balance, than men and boys.9

Lynall believes that concussions and gender deserve more study.

“Male and female often get lumped together,” he said. “And we know that males and females don’t respond the same way to concussions. Athletes need to be honest about symptoms they’re suffering, and frankly, I think that women are more honest about it than men. I think there is some physiological basis to it, but I also think that some of it is reporting.”

Baumann and Howell posit that there are both physical and hormonal reasons why girls and women not only suffer more concussions, but also take longer to heal. In particular, both suggest that since females have less neck strength than males, they aren’t able to sustain a potentially concussion-causing hit as effectively.

Assessing head injuries

A series of tests, collectively referred to as SCAT (Sports Concussion Assessment Tool), is available for coaches and trainers to use to assess concussions. The tests have different “levels” that can be used for varying age groups. For example, the Child SCAT-5 test is for kids aged 5 to 12 years. 10 The checklist includes an observation section, a symptom check, a memory test, and a concentration test, as well as other sections.

In addition, the Centers for Disease Control and Prevention’s “Heads Up: Concussion in Youth Sports” initiative has been effective in helping youth coaches identify and sometimes prevent concussions on the playing field, according to a 2012 Journal of School Health evaluation of the initiative.11

“Athletic trainers are the ones who are there on a day-to-day basis, they develop a rapport with [athletes] and can identify mood changes pretty quickly,” Howell said. “But concussion is a clinical diagnosis at this point, so there is no ‘gold standard.’”

Based on the research, both Lynall and Howell agree that getting an athlete off the field as quickly as possible after a concussion is of paramount importance.

While it’s been shown that the effects of a concussion can be long lasting, symptoms are often most obvious immediately after the concussion, making an athlete (or anyone else) with a head injury less able to complete simple tasks.

Howell recently looked at near point of conversion (NPC, a visual assessment) and gait deficits in adolescents after a sport-related concussion. The study,12 published in May in the Clinical Journal of Sport Medicine, showed that 55% of concussed adolescents had a receded NPC; these participants exhibited significant gait-related deficits compared with healthy controls, including slower gait speed and shorter stride length. Concussed adolescents with normal NPC did not demonstrate gait deficits.12

The obvious question, then, is when should the youth athlete return to the playing field? Many of the screening tests used by physicians and trainers alike are static, but sports are dynamic. As mentioned earlier, Howell is studying dual-task gait situations, which he believes is a step (pun intended) in the right direction.

“I think that dual gait is a nice testing paradigm because most people walk with a similar pattern over time,” he said. “A lot of other sort of balance paradigms aren’t really something they practice all the time … so, you don’t usually stand around on one foot with your eyes closed every day.”

Although young athletes may feel a certain amount of pressure to return to the playing field, Howell is quick to say that “toughing it out” in the case of a concussion is the worst option. Whether a screening test is static or dynamic, determining when an athlete should return to play is not an exact science.

Because of that, Lynall recommends “hyper vigilance” on the part of coaches and trainers when a concussed youth athlete does return to the field. It is critical, he said, for trainers, coaches, and parents to be on the look for issues with gross motor skills and balance.

“It’s tricky,” Lynall said. “I don’t think we have the ability right now to say, ‘Well, you have a concussion, you should sit out for THIS amount of time.’ We just don’t have that information. I talk to clinicians and they want a firm answer to be able to know when a youth athlete can come back, but we just don’t know.”

Jill R. Dorson is a freelance writer based in San Diego, CA.

  1. Lynall R, Mauntel T, Pohlig R, et al. Lower extremity musculoskeletal injury risk after concussion recovery in high school athletes. J Athl Train 2017;52(11):1028-1034.
  2. Rutland-Brown W, Langlois J, Thomas K, Xi Y. Incidence of traumatic brain injury in the United States. J Head Trauma Rehabil 2006;21(6):544-548.
  3. Kardouni J, Shing T, McKinnon C, et al. Risk for lower extremity injury after concussion: a matched cohort study in soldiers. J Orthop Sports Phys Ther 2018:1-25.
  4. Howell D, Buckley T, Lynall R, Meehan W. Worsening dual-task gait costs after concussion and the association with subsequent sports-related injury. J Neurotrauma 2018 May 3. [Epub ahead of print]
  5. Grants L, Powell B, Gessel C. Gait deficits under dual-task conditions in the concussed adolescent and young athlete population: a systemic review. Int J Sports Phys Ther 2017;12(7):1011-1021.
  6. Lynall R, Mauntel T, Padua D, Mihalik J. Acute lower extremity injury rates increase after concussion in college athletes. Med Sci Sports Exerc 2015;47(12):2487-2492.
  7. Dick R. Is there a gender difference in concussion incidence and outcomes? Br J Sports Med 2009;43:46-50.
  8. Comstock DR, Currie DW, Pierpoint LA, et al. An evidence-based discussion of heading the ball and concussions in high school soccer. JAMA Pediatr 2015;169(9):830-837.
  9. Bauman S. Gender differences in clinical presentation and recovery of sports-related concussion. Abstract presented at the Pink Concussion 2016 International Summit, Female Brain Injury in Sports, Domestic Violence and Military Service, Georgetown University, Washington, DC.
  10. Child SCAT5. Sport Concussion Assessment Tool. British Journal of Sports Medicine website. Accessed June 14, 2018.
  11. Covassin T, Elbin RJ, Sarmiento K. Educating coaches about concussion in sports: evaluation of the CDC’s “Heads Up: concussion in youth sports” initiative. J Sch Health 2012;82(5):233-238.
  12. Howell D, O’Brien M, Raghuran A. Near point of convergence and gait deficits in adolescents after sports-related concussions. Clin J Sport Med 2018;28(3):262-67

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