Faculty Collaboration Database

Head Impact Density: A Model To Explain the Elusive Concussion Threshold. J Neurotrauma 2017 Oct 01;34(19):2675-2683

Date

04/07/2017

Pubmed ID

28381134

Pubmed Central ID

PMC5647505

DOI

10.1089/neu.2016.4767

Scopus ID

2-s2.0-85030104736 (requires institutional sign-in at Scopus site)   57 Citations

Abstract

Concussion is a heterogeneous injury occurring throughout a range of impact magnitudes. Consequently, research focusing on a single or set of variables at the time of injury to understand concussive biomechanics has been thwarted by low injury prediction sensitivity. The current study examined the role of Impact Density in estimating concussive injury risk. Head impact data were collected across seven high school football seasons with the Head Impact Telemetry System (HIT System). Over the study period, 29 concussions were included for data analysis. The linear acceleration of the concussive impact was matched to a Control athlete, along with impacts in the 24 h before. Linear and rotational acceleration for the 19 impacts leading into the final event and the cumulative accelerations over time were evaluated. Analyses indicated no difference in impact counts within the final 24 h, or impact magnitudes for linear and rotational acceleration among the final 20 impacts (p > 0.05). A novel metric, Impact Density, was calculated from the final 20 impacts by summing the acceleration magnitude divided by time from the previous impact. Analyses indicated the Concussed athletes incurred a significantly higher linear (concussed: 255.4g/sec (standard error of the mean [SEM] = 40.1), controls:145.4g/sec (SEM = 23.8), p = 0.016), and rotational (Concussed:10311.3 rad/s/s/s (SEM = 1883.7), Controls: 6083.8 rad/s/s/s (SEM = 1115.9), p = 0.029) Impact Density than the Control athletes. Similar to other investigations, there was no difference in individual linear or rotational impact magnitude in the 20 impacts before and including the injury. The measure of Impact Density, however, revealed differences between the Concussed and Control athletes. These data suggest that the biomechanical threshold for concussion fluctuates downwardly with a greater impact magnitude and number with a return to pre-impact levels with time, suggesting physiological vulnerability to repeated head impacts. The current results highlight that time between impacts, not just impact magnitude, influences risk for concussion.

Author List

Broglio SP, Lapointe A, O'Connor KL, McCrea M

Author

Michael McCrea PhD Professor in the Neurosurgery department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Acceleration
Accelerometry
Adolescent
Athletes
Biomechanical Phenomena
Brain Concussion
Football
Head Protective Devices
Humans
Rotation