Nelson-Cradle Rule Decreases Concussion Injury Rates In High School Wrestlers

Wrestling is among the sports with the highest rate of sport-related concussion (SRC), as researchers indicate that between 2013 to 2018 high school wrestlers experienced a SRC rate of 4.83 concussions per 10,000 athlete exposures. This high SRC rate necessitates study into preventative policy particularly in high school settings (e.g., Nelson-Cradle rule) and the association with SRC injury rates. PURPOSE: To evaluate if mandating the Nelson-Cradle as an illegal hold/maneuver decreases concussion incidence in high school wrestling athletes. METHODS: An epidemiology study of athletes diagnosed with SRC participating in Michigan High School Athletic Association (MHSAA) wrestling from 2015/16-2019/20, 2021/22 academic years. SRCs were recorded in MHSAA Head Injury Reporting System by licensed athletic trainers, coaches, or administrators. The Nelson-Cradle rule was enacted during the 2018-2019 academic year and stated that it is a now an illegal hold/maneuver. Pre-rule years included 2015/16-2017/18 and post-rule years included the 2018/19, 2019/20, 2021/22 academic years. The 2020-21 year was removed due to the COVID-19 pandemic. Clinical incidence and relative risk ratios were calculated to compare pre- and post-rule SRC rates (95% confidence intervals (CI)). RESULTS: Clinical incidence per 1,000 athletes in years prior to the Nelson-Cradle rule were 25.52 (95% CI [22.46,28.87]) in 2015-16, 26.15 (95% CI [23.05,29.54]) in 2016/17, and 24.90 (95% CI [21.85,28.26]) in 2017/18. Clinical incidence per 1,000 athletes for post Nelson-Cradle rule years were 22.19 (95% CI [19.32,25.36]) in 2018/19, 22.09 (95% CI [19.27,25.20]) in 2019/20 and 19.98 (95% CI [17.20,23.08]) in 2021/22. The rate of SRC in wrestling was significantly higher before the Nelson-Cradle became an illegal maneuver (risk ratio 1.2, 95% CI [1.07,1.33]). CONCLUSION: SRC rates were significantly higher in years prior to the Nelson-Cradle rule suggesting a potential protective effect on policy for reducing concussion rates. More work is needed to determine other factors potentially influencing concussion rates in wrestling, and the association with additional policy implementation and overall injury incidence.