Purpose: This study compares the frequency and severity of head impacts sustained by football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of single-impact severity measures to diagnosed injury.
Methods: One thousand two hundred eight players from eight collegiate football teams and six high school football teams wore instrumented helmets to measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one sustained three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd severity index, head injury criteria (HIC15), and change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operating characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis.
Results: Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed after head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (area under the curve = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (P = 0.01), which are derived from linear acceleration (peak linear, HIC15, Gadd severity index, and Δv).
Conclusions: Players sustained more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. In addition, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion.
1Simbex, Lebanon, NH; 2Thayer School of Engineering, Dartmouth College, Hanover, NH; 3Alpert Medical School of Brown University and Rhode Island Hospital, Providence, RI; 4Virginia Tech-Wake Forest, Center for Injury Biomechanics, Blacksburg, VA; 5University of Michigan School of Kinesiology, Ann Arbor, MI; 6Michigan NeuroSport, Ann Arbor, MI; 7Department of Psychiatry, Dartmouth Medical School, Hanover, NH; 8Matthew Gfeller Sport-Related Traumatic Brain Injury Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC; 9Department of Intercollegiate Athletics, University of Oklahoma, Norman, OK; 10Departments of Orthopedics and Athletics, University of Oklahoma, Norman, OK; 11Edward Via College of Osteopathic Medicine, Blacksburg VA; and 12Departments of Orthopaedic Surgery and Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA
Address for correspondence: Jonathan G. Beckwith, M.S., Simbex, 10 Water Street, Suite 410, Lebanon, NH 03766; E-mail: firstname.lastname@example.org.
Submitted for publication May 2012.
Accepted for publication October 2012.