Does the MLB's collision at home plate rule change prevent concussion injuries in catchers?

Background: In 2013, appropriate conduct of both the catcher and baserunner at the home plate was outlined with the addition of rule 7.13. This new rule was mandated in order to protect athletes from 'egregious' collisions at the home plate. The aims of this study were to quantify the impact of the Collision at Home Plate rule on concussion rates among MLB catchers, and time spent on the DL with concussion symptoms, before and after rule 7.13 was officially enacted (2012-2013, 2015-2016). Hypothesis: We hypothesized that the rate of concussions suffered by MLB catchers would be significantly lower after the enactment of rule 7.13 and that there would be no significant difference in time spent on the DL between the two cohorts. Study design: Retrospective Cohort Methods: The data was compiled using publicly available information extracted from MLB transactions. All MLB catchers placed on the DL for a concussion injury from 2012 to 2013 and 2015 to 2016 were included in this study. Relative risk (with 95% CI) was calculated by using the number of injuries per 1,0000 athletic exposures for the 2 seasons under the rule change (2015-2016) versus the previous 2 seasons (2012-2013). Results: Among catchers the relative risk of concussion per 1000 athletic exposures was 0.31 (95% CI, 0.11-0.85) when comparing the 2 seasons after the introduction of rule 7.13 (2015, 2016) versus the 2 seasons before (2012, 2013). There was no significant statistical difference in average time catchers spent on the DL for concussion injuries when comparing the 2012 and 2013 seasons versus 2015 and 2016. Conclusions: The MLB's rule limiting home plate collisions significantly reduced the number of concussions suffered by MLB catchers.