Quantifying Head Impact Exposure, Mechanisms and Kinematics Using an Instrumented Mouthguard in Female High School Lacrosse

BACKGROUND: There is growing concern for the neurological effects of repetitive head impacts in sports, and girls’ lacrosse represents a popular but understudied sport regarding head impact exposure. Current debate exists over the need for enhanced protective equipment, and it is important to quantify head impact exposure and biomechanics to inform policy discussions and rule changes for improved protection. PURPOSE: To quantify the head impact biomechanics, by impact mechanism and direction, of female high school lacrosse players during games using an instrumented mouthguard. METHODS: A female high school varsity lacrosse team wore the Stanford Instrumented Mouthguard during competitive games for the 2019 season. Video footage was reviewed to confirm head impact events and remove false-positive recordings. For each impact event, the mechanism was coded as stick contact, player contact, fall, or ball contact, and the site was coded as face/jaw, forehead, crown, side, rear or indirect (i.e. body impact with no head contact). Head impact rates were calculated per athlete exposure (AE, defined as a single player participating in a game). RESULTS: Sensor data were recorded for 15 players for 14 games and 97 AEs. During games, 31 sensor-recorded head impacts were video-confirmed resulting in a pooled average head impact rate of 0.32 impacts/AE. The 31 video-confirmed impacts were distributed among stick contacts (17, 54.8%), player contacts (12, 38.7%), and falls (2, 6.5%). There were no ball impacts. The associated peak kinematics are presented in Figure 1.1. The most common impact site was the side (11, 35.5%), followed by face/jaw (8, 25.8%), forehead (2, 6.5%), and crown (2, 6.5%). There were no impacts to the rear of the head and 8 (25.8%) impacts were indirect. The associated peak kinematics are presented in Figure 1.2. CONCLUSION: Stick impacts were the most common impact mechanism and resulted in the highest peak linear and angular kinematics, which may help explain why they are the most common cause of head injury in female lacrosse. By quantifying the head impact exposure, kinematics and mechanisms in female high school lacrosse, targeted injury preventions can be developed, such as rule changes and protective equipment.