Batted Ball Injury Study
October 9, 2006

ANNUAL REPORT

BATTED BALL INJURIES TO THE PITCHER

FREDERICK O. MUELLER, Ph.D. 1
STEPHEN W. MARSHALL, Ph.D 2


Departments of Exercise and Sport Science1 and Epidemiology2
University of North Carolina at Chapel Hill


PROPOSAL SUMMARY

The researcher’s proposal was to conduct a three year observational epidemiological study on injuries from batted balls to the pitcher, comparing the wood bat to the aluminum bat. Data on injuries from aluminum bats is being drawn from the National Collegiate Athletic Association’s Injury Surveillance System. Data on injuries from wood bats is being prospectively collected by Drs. Mueller and Marshall in the summer collegiate baseball leagues around the country.

The study is collecting data on pitcher’s acute injuries in games or practices, with a focus on line drive batted balls. This study will provide an answer to the question of whether the use of aluminum bats in baseball increases the risk of injury to pitchers from batted balls, relative to use of the wood bat. The study is collecting data for three years – 2005, 2006, 2007.

SAMPLE OF TEAMS

Prior to the data collection period contact was made with the National Collegiate Athletic Association (NCAA) concerning the use of their baseball data from their Injury Surveillance System. They agreed to share data on injuries to the pitcher from batted balls from the aluminum bat. During the 2006 season the NCAA collected baseball data from 55 teams. We have combined this data with the data from 38 teams that provided data in 2005.

During the summer of 2005 we collected data from 129 summer league teams. In summer of 2006 we collected data from 117 teams. Prior to the 2005 season we mailed letters explaining the research, human subject information, and copies of the injury form to all leagues and teams. In the 2006 season, we re-contacted all teams. The research assistant assisted in all of the mailings, contacted the summer league teams by telephone during the season, and traveled to eight of the 15 leagues to observe games and meet the coaches.


INTERIM ANALYSIS – YEARS 1 & 2

This interim analysis is presented by combining the 2005 and 2006 data. The interim analysis is based the number of injuries to pitchers from a line drive batted ball in which the pitcher had to leave the game, divided by the total number of balls in play. Balls in play are calculated by taking the total number of at-bats and subtracting strike outs and bases on balls in order to give a true picture of how many balls are actually hit into the field of play. We computed this injury rate in the NCAA and in the summer leagues. The ratio of these two rates (NCAA injury rate divided by summer league injury rate) is a measure of the increased “risk” of injury (to pitchers from line drives) in the NCAA (aluminum bats) relative to summer leagues (wood bats).

The total number of line drive injuries to the pitchers from batted balls on the NCAA teams was 8 injuries on 38 teams in 2005 and 9 injuries on 55 teams in 2006, for a total of 17 injuries over the 2 years. The total number of balls in play on these teams was estimated to be 40,500 in 2005 and 58,600 in 2006. Thus, the average rate of line drive batted ball injury for NCAA pitchers was 0.17 per 1,000 balls in play. All of the NCAA injuries over both years were contusions to the arm, hand, foot, or lower leg.

The total number of line drive injuries to the pitchers from batted balls on the summer league teams was 10 injuries on 129 teams in 2005 and 5 injuries on 117 teams in 2006, for a total of 15 injuries over the 2 years. The total number of balls in play on these teams was 119,000 in 2005 and 107,900 in 2006. Thus, the rate of line drive batted ball injury to summer league pitchers was 0.07 per 1,000 balls in play. A majority of the summer league injuries were contusions to the hand, arm, and lower leg. There was also one fractured hand, one fracture to the face, one fractured skull, two contusions to the face, and one concussion. The summer league injuries were more serious than the college team injuries.

The ratio of these rates (NCAA divided by summer leagues) is 2.6, with a 95% confidence interval of 1.3 to 5.2 and a confidence limit ratio of 4.0 with a p-value of 0.005. The current interpretation of this number is that we have too few injuries – based on only 17 NCAA and 15 summer injuries - to reach a definitive conclusion. We are in year 2 of a 3-year study. The only firm conclusion that can be made based on the first two years of data is that the rate of line drive ball injury to a pitcher is low in both the NCAA and the summer leagues.

The injuries in summer league were more severe than the injuries in the NCAA. Furthermore, 5 of the 15 summer league injuries (33%) involved the head and face (compared to none in the NCAA).

2007 DATA COLLECTION

During the 2007 season the study will proceed as in year two. After year three, the results will analyzed, a final report written, and a paper prepared for publication in the medical literature.

Our opinion is that there is a case for renewing the study for an additional 3 years. This is because the rate of injury is even lower than we originally projected. Our opinion is a 6-year study is required to address this issue. If the study were renewed, the results from the first 3 years would be combined with the results from years 4 to 6 to yield approximately 100 injuries. At that point, there would be a much firmer basis for making a definitive statement.


ACKNOWLEDGMENTS

We wish to thank Randy Dick and Jill Corlette at the NCAA for their assistance with providing reports from the NCAA ISS database. We also acknowledge the work of Johna K Mihalik, research assistant on the study and doctoral student in UNC’s Sports Medicine Research Laboratory.




Frederick O. Mueller, Ph.D. Stephen W. Marshall
Professor, Exercise and Sport Science Associate Professor, Epidemiology