ABSTRACT
OBJECTIVES: In 2018 the NFL instituted playing rule article 8, which aimed to help decrease sport related concussion (SRC) by broadening the helmet-hit rule, making it a foul when a player lowers his head to make contact with his helmet against an opponent. Previous studies have demonstrated that the rate of lower extremity injuries increased following the institution of the targeting rule in NCAA football. The objective of this study was to determine if playing rule article 8 unintentionally led to a significant increase in the rate of lower extremity injuries sustained by NFL players during regular season games. METHODS: This study was a retrospective review of all NFL players who were placed on the publically available injury reports for a lower extremity injury from the 2016-2017 through 2019-2020 regular seasons. With article 8 taking effect starting with the 2018-2019 season, players were assigned to a pre- or post-rule cohort based on date of injury for purposes of injury rate comparison. Injury rates were calculated per 1000 athletic exposures (AE). Incidence rate ratio (RR) with 95% confidence intervals (CI) compared injury rates between the two cohorts. RESULTS: There was a 3% decrease in the lower extremity injury rate in 2018-2019 to 2019-2020 compared with 2016-2017 to 2017-2018, however this was not statistically significant (33.6 versus 34.3/1000 AEs, respectively; RR, 0.97; 95% CI 0.92-1.04). There was a 40% decrease in the SRC rate when comparing the post- to the pre-article-8 cohort (3.3 vs. 5.5/1000 AEs, respectively; RR 0.60; 95% CI 0.50-0.73). CONCLUSIONS: The rate of lower extremity injuries and players placed on the injury reserve over the past two NFL seasons following the enactment of playing rule article 8 has not significantly increased. However, the average games missed due to lower extremity injuries significantly increased under playing rule article 8, which suggests that the severity of lower extremity injuries possibly increased. LEVEL OF EVIDENCE: IV Diagnostic.