Purpose: Concussions are commonly undiagnosed in an athletic environment because the postinjury signs and symptoms may be mild, masked by the subject, or unrecognized. This study compares measures of head impact frequency, location, and kinematic response before cases of immediate and delayed concussion diagnosis.
Methods: Football players from eight collegiate and six high school teams wore instrumented helmets during play (n = 1208), of which 95 were diagnosed with concussion (105 total cases). Acceleration data recorded by the instrumented helmets were reduced to five kinematic metrics: peak linear and rotational acceleration, Gadd severity index, head injury criterion, and change in head velocity (Δv). In addition, each impact was assigned to one of four general location regions (front, back, side, and top), and the number of impacts sustained before injury was calculated over two periods (1 and 7 days).
Results: All head kinematic measures associated with injury, except peak rotational acceleration (P = 0.284), were significantly higher for cases of immediate diagnosis than delayed diagnosis (P < 0.05). Players with delayed diagnosis sustained a significantly higher number of head impacts on the day of injury (32.9 ± 24.9, P < 0.001) and within 7 d of injury (69.7 ± 43.3, P = 0.006) than players with immediate diagnosis (16.5 ± 15.1 and 50.2 ± 43.6). Impacts associated with concussion occurred most frequently to the front of the head (46%) followed by the top (25%), side (16%), and back (13%) with the number of impacts by location independent of temporal diagnosis (χ2(3) = 4.72, P = 0.19).
Conclusions: Concussions diagnosed immediately after an impact event are associated with the highest kinematic measures, whereas those characterized by delayed diagnosis are preceded by a higher number of impacts.
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 August 2012.