Visual-Spatial Factors Influencing ACL Injury Risk

📝 Weekly paper summary

Visual-Spatial Attentional Performance Identifies Lower Extremity Injury Risk in Adolescent Athletes (Avedesian et al., 2022)

Category

Prospective Observational Study

Context

Previous research has emphasized movement-related factors that can increase one's risk of tearing one's Anterior Cruciate Ligament (ACL) or sustaining other knee injuries. These factors are often directly (e.g., joint kinetics and kinematics) or indirectly (e.g., the strength of lower extremity muscles) related to the causes and consequences of motion associated with an ACL injury.

However, deficits in cognitive and oculomotor capabilities may also indirectly contribute to how someone moves in their sport and, thus, their risk of ACL injury. For example, slower reaction times could conceivably result in movement strategies that amplify biomechanical risk factors (e.g., increased knee valgus motion). Although some data in college-aged athletes suggests that slower reaction time is associated with a 2-3x larger risk of sustaining a lower extremity knee injury, nobody has replicated these findings with adolescent athletes. Therefore, this study aimed to assess if adolescent athletes' baseline cognitive and oculomotor measures were associated with increased risk for knee injuries during their sports season. The authors hypothesized they would find an association between knee injuries and reduced performance on these cognitive and oculomotor tasks.

Correctness

Although it's low-hanging fruit to comment on, it's important to highlight that the authors recruited 446 adolescent athletes (274 male football players, 172 female soccer players). In total, there were 68 lower extremity injuries throughout the season. Therefore, this is one of the more extensive studies examining associations to quantify knee injury risk.

There are a few delimitations to consider when interpreting these findings. First, although their Attention-Network Tasks, Cued Switching Tasks, and Near Point of Convergence assessments captured an array of cognitive and oculomotor capabilities of the athletes, the perceptual stimuli are still quite different from their actual sport. Previous data have demonstrated the importance of maintaining similar perception-action coupling during training to reduce the risk of ACL injuries (Tidman et al., 2020). Therefore, I think the findings in this study would be more robust if we combined motion analysis and virtual reality technology to assess how people moved in perceptually-relevant contexts. Although the authors intentionally used these tasks since they are inexpensive and accessible clinical tests, I'd love to do this work one day using VR headsets. But it's on the backburner for now.

Second, it's important to contextualize how the authors defined injuries in this study. It's common in the literature to define an injury as the authors did in this paper, which was (pg. 2):

"(1) any acute occurrence that prevented athletes from continuing participation in the current sporting event and required evaluation by the athletic trainer or (2) an occurrence that limited sports participation the following day. Fractures, dislocations, contusions, and overuse injuries were excluded from the analyses because we were most interested in acute injuries that would likely result from errors or delays in neuromuscular control associated with visual-spatial performance"

Therefore, since there was no motion data, we can't tease out what the injuries may have been or why people missed training. For example, it's a known problem that recorded injuries are sometimes as innocuous as athletes missing practices for class. I'm not suggesting that's what happened in this study or that we shouldn't trust the authors' data, but rather to be careful that since there was no formal diagnosis, we should tread more lightly relative to if we had scans to show tissue damage.

Third, since there is no motion data, it's hard to determine whether any differences (or lack thereof) in injuries are attributable to how people moved. For example, it's possible that decreased cognitive and oculomotor performance would result in athletes putting themselves in situations with increased contact with other players. Since the biomechanical risk factors we often study are associated with non-contact injuries, perhaps these cognitive and oculomotor tests pick up injury risk mechanisms related to contact injuries. It's hard to say either way without more data, so we need to interpret these data with caution until researchers have conducted more experiments.

Contributions

• A reaction time (RT) of greater than 32.8ms was associated with a 2.62x greater risk of lower extremity injury; every 10ms increase in RT was associated with a 15% increased risk of injury.
• No other tests discriminated between those who did versus did not sustain a knee injury.
• Future assessment protocols should consider measuring RT during  Attention-Network Tasks.

🧠 Fun fact of the week

There used to be a rumour that hippos produce pink milk. Although this would be fun, it's not a fact. Instead, they secrete a blend of hipposudoric and norhipposudoric acid which, combined, serve as a natural form of sunscreen and moisturizer for their sensitive skin and protects them from harmful bacteria when they're in the water! This secretion starts colourless (like human sweat) but turns bright orange-red in the sun. Some could mix with the milk and give it a pinkish hue when the secretions are at their peak. Therefore, the pink milk theory is just a rumour, and the actual fun fact is the remarkable properties of their oily secretions!

🎙 Podcast recommendation

Again, I'm sharing this so I commit to listening to it soon!

🗣 Quote of the week

"You can either experience the pain of discipline or the pain of regret. The choice is yours."

- Zig Ziglar