Abstract
Researchers have been collecting head impact data from instrumented football players to characterize the biomechanics of concussion for the past 15 years, yet the link between biomechanical input and clinical outcome is still not well understood. We have previously shown that even though concussive biomechanics might be unremarkable in large datasets of head impacts, the impacts causing injury are of high magnitude for the concussed individuals relative to their impact history. This finding suggests a need to account for differences in tolerance at the individual level. In this study, we identified control subjects for our concussed subjects who demonstrated traits we believed were correlated to factors thought to affect injury tolerance, including height, mass, age, race, and concussion history. A total of 502 college football players were instrumented with helmet-mounted accelerometer arrays and provided complete baseline assessment data, 44 of which sustained a total of 49 concussion. Biomechanical measures quantifying impact frequency and acceleration magnitude were compared between groups. On average, we found that concussed subjects experienced 93.8 more head impacts (p = 0.0031), 10.2 more high magnitude impacts (p = 0.0157), and 1.9 × greater risk-weighted exposure (p = 0.0175) than their physically matched controls. This finding provides further evidence that head impact data need to be considered at the individual level and that cohort wide assessments may be of little value in the context of concussion.
Highlights
Researchers have been collecting head impact data from instrumented collegiate football players to characterize the biomechanics of concussion for the past 15 years.[5,11,12,15,20,24,28,33] While these efforts have advanced our understanding of the impact characteristics associated with injury, the link between biomechanical input and clinical outcomes is still not well understood
For any given concussive head acceleration, there might be 1000 other head impacts in the dataset that look just like it and do not cause injury. This leads to the question of: what is unique about the specific impacts causing injury? This paper presents an exploratory analysis aimed at explaining some of the variance in concussion tolerance observed in these datasets
We have previously shown that even though concussive biomechanics might be unremarkable in large datasets of head impacts, the impacts causing injury are of high magnitude for the concussed individuals relative to their impact history.[32]
Summary
Researchers have been collecting head impact data from instrumented collegiate football players to characterize the biomechanics of concussion for the past 15 years.[5,11,12,15,20,24,28,33] While these efforts have advanced our understanding of the impact characteristics associated with injury, the link between biomechanical input and clinical outcomes is still not well understood. For any given concussive head acceleration, there might be 1000 other head impacts in the dataset that look just like it and do not cause injury. This leads to the question of: what is unique about the specific impacts causing injury? Similar biomechanical inputs (impact location and acceleration magnitude) should produce similar injury responses (symptom severity and duration) between injured subjects if all other factors between individuals were equal. Biological variance, defined here as intrinsic inter-individual differences between human subjects, is commonly observed in injury biomechanics research, and largely explains why a threshold for concussion has not been identified
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