Single season re-injury risk after concussion and lower extremity injury among male, collision sport, high school athletes.

OBJECTIVES:Research suggests that a recent concussion increases subsequent lower extremity injury risk; however, data in high school athletes is limited. This study evaluates the association between concussion and subsequent injury risk among male, collision sport, high school athletes over a single season. DESIGN:Retrospective cohort study. METHODS:Data were obtained from 2005/06-2014/15 in the High School Reporting Information Online database. A two stage, multi-method matching process was used to identify athletes who suffered multiple injuries over a single athletic season. Demographics and injury characteristics were compared with Chi square and Student's t-tests. Multiple Cox Proportional Hazards regression analysis was used to test whether index injury type was associated with hazard of subsequent injury following return to play from index injury. RESULTS:Overall 1364 HS athletes sustained 2 injuries over a single athletic season (subsequent injury within 45 days of the index injury). Index injuries included 686 (50.2%) lower extremity injuries, 417 (30.6%) upper extremity injuries, and 261 (19.1%) concussions. Hazard of subsequent concussion was increased in the index concussion group relative to the index lower extremity injury group [hazard ratio (HR): 1.60, 95% CI: 1.15-2.23, p = 0.0052]. Hazard of a subsequent lower extremity injury was not significantly different for the index lower extremity injury group relative to the index concussion group [HR: 1.27, 95% CI: 0.98-1.65, p = 0.0728]. CONCLUSIONS:History of recent concussion or recent lower extremity injury are both risk factors for subsequent lower extremity injury in male, collision sport, high school athletes.