Background: The purpose of this study was to investigate the incidence of anterior cruciate ligament (ACL) injuries in Missouri high school female and male soccer players during the 2011-2013 seasons, using a single postseason survey sent to coaches. Our hypothesis is a single postseason survey be a feasible method to measure a large number of athletic exposures (AEs) and ACL injuries. We also hypothesize that “traditional” methods for calculating athletic exposures likely underestimate the actual burden of ACL injuries in high school soccer matches. Methods: The study was IRB approved through the University of Missouri. A web-based survey was developed and sent to every girls and boys high school soccer coach in Missouri using a Missouri State High School Activities Association (MSHSAA) database. In order to calculate AEs, questions were asked about the average number of athletes who participated in tryouts, practices, and matches along with the specific number of tryouts, practices, and matches for the 2011-2012 and 2012-2013 seasons. Coaches were also asked the number of ACL injuries their team suffered. No medical personnel were involved in filling out the surveys. Athletic exposures (AEs) were calculated using the formulas below. Match athletic exposures were calculated using a “traditional” method and also an “athlete at risk” method. The primary outcome measure was ACL injuries. Formulas for Calculation of Athletic Exposures (AEs) Tryouts & Practice= (a*A) + (b*B) Match (Traditional)= (c*C) Match (Athlete at Risk)= (11*C) a = average number of players participating in tryouts A = number of tryout sessions b = average number of players participating in practices B = number of practices in a season c = average number of players participating in matches C = number of matches in a season Results: In total, 885 coaches were sent surveys and 160 (18.1%) coaches responded, with 84 coaches representing girls soccer teams and 76 representing boys teams. A total of 323,010 AEs (160,756 female and 162,254 male) were reported of which 228,608 AEs (71%) took place in practices. 94,402 AEs occurred in matches using the “traditional” method and 61,963 AEs in matches using the “athlete at risk” method. 36 ACL injuries (28 female and 8 male) were reported. Of the 28 female ACL injuries, 25 happened during high school soccer activities (23 match, 2 practice). 3 ACL injuries occurred outside of high school soccer activities (1 club soccer, 1 volleyball, 1 unknown.) All 8 male ACL injuries were suffered during a high school match. Female athletes had an ACL injury rate of 0.16/1000 AEs compared to male athletes 0.05/1000 AEs (Table 1). Female athletes had a practice ACL injury rate of 0.02/1000 AEs and there were no ACL injuries suffered by male athletes in practice. Female athletes had a match ACL injury rate of 0.47/1000 AEs using “traditional” method and 0.70/1000 AEs by the “athlete at risk” method. Male athletes had a match ACL injury rate of 0.18/1000 AEs “traditional” method and 0.28/1000 AEs “athlete at risk” method (Figure 1). Female high school soccer athletes had a 3.2x greater risk of ACL tear than male high school soccer athletes. Female athletes were 26x more likely to tear their ACL in a match compared to practice. ACL match injury rates were 50-55% higher using the “athlete at risk” method compared to “traditional” methods for calculating match injury rates. Conclusion/Significance: A single postseason survey sent to coaches was successful in measuring AEs and ACL injury rates for a large population of high school soccer athletes. This represents an economical and feasible mechanism compared to previous studies (Table 2) to measure ACL injury rates for a high number of teams. It also allows ACL injury rates to be measured for schools and teams that do not have certified athletic trainers. “Traditional” methods for calculating match ACL injury rates greatly under represent ACL injuries compared to the “athlete at risk” method which is more representative of true injury risk exposure. A very high percentage of ACL injuries occurred during matches even though matches were responsible for only 29% of AEs. If future studies have limited resources, they should consider not recording practice AEs and ACL injuries since the likelihood of an ACL injury occurring during practice is very low compared to a match. [Table: see text][Table: see text][Figure: see text]
Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes
