[1] Childrens Hosp Philadelphia, Div Emergency Med, Philadelphia, PA 19104 USA
[2] Childrens Hosp Philadelphia, Ctr Injury Res & Prevent, Philadelphia, PA 19104 USA
[3] Univ Penn, Dept Biostat & Epidemiol, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, Philadelphia, PA 19104 USA
[5] Childrens Hosp Philadelphia, Sports Med & Performance Ctr, Philadelphia, PA 19104 USA