Original Research

Injury Trends in Major League Baseball Over 18 Seasons: 1998-2015

Author and Disclosure Information

Since Major League Baseball (MLB) expanded to its current size of 30 teams in 1998, a comprehensive and longitudinal study of injury trends has not been performed. The purpose of this work is to report the epidemiology of injuries in MLB over that time utilizing disabled list (DL) data. Additionally, we sought to determine the financial impact of these injuries for MLB teams. During this analysis, we focused special attention on injuries of the medial ulnar collateral ligament (MUCL) and conducted a comprehensive review of all MUCL reconstructions ever performed on MLB players.

Over the study period, there were a total of 8357 DL designations (mean of 464 annually). Players lost a total of 460,432 days (25,186 days annually) due to injury. Both the number of DL assignments and number of DL days increased from year to year (P < .001 and P = .003, respectively). Average length of DL assignments remained steady over time at 55.1 days (P = .647). Although shoulder injuries decreased (P = .023), this was met with a reciprocal increase in elbow injuries (P = .015). The average annual cost of designating players to the DL was $423,267,634 and a total of $7,618,817,407 was spent over the entire 18 seasons. Regarding MUCL injuries, a total of 400 MUCL reconstructions were performed in MLB players between 1974 and 2015, and the mean time to return to MLB competition was 17.1 months. The annual incidence of MUCL reconstructions increased dramatically from year to year (P < .001) and nearly one-third (n = 131, 32.8%) of all procedures performed over the 42-year period occurred in the last 5 years (2011 to 2015). In summary, overall injury rates and DL assignments continue to rise. Although shoulder injuries are declining, this improvement is countered by increasing elbow injuries, and these injuries continue to represent a significant source of lost revenue.



While the exact origins of the game of baseball are commonly debated, one thing is certain: statistics have been an integral part of the game since its existence.1-3 This is true at nearly every level of baseball, especially in Major League Baseball (MLB). As our knowledge and technical capabilities advance, new statistical measures of baseball performance are added at a rapid pace.1,3 One example is the Pitch f/x video tracking system (Sportvision, Inc.), which now analyzes over 60 variables on each of the estimated 660,000 pitches thrown in the MLB annually. In addition to measuring performance and production, these advancements are being leveraged to better understand the epidemiology and impact of injuries in MLB players.4,5 As with any sport, performance at the most elite level is highly dependent upon player health and functional capacity. Accordingly, player injuries can have a profound impact not only on individual performance but also on the success of the team as a whole.

The first epidemiologic study of injuries in professional baseball was published by Conte and colleagues4 in 2001. This work utilized publically available disabled list (DL) data to perform a comprehensive review of injury patterns in MLB from 1989 to 1999. They demonstrated that injuries were on the rise and that pitchers were more commonly injured (48.4% of all DL reports) and had greater time out of play compared to players of other positions.4 Shoulder and elbow injuries were responsible for 49.8% of all DL assignments, distantly followed by knee (7.3%), wrist/hand (6.1%), and back (5.0%).4 In a later study, Posner and colleagues5 analyzed DL data spanning the 2002 to 2008 seasons. Similarly, they found that injuries continued to increase, and over half (51.2%) of DL assignments occurred secondary to upper extremity injuries.5 Although the DL is primarily designed as a roster management tool rather than an injury database, it has provided valuable epidemiologic injury information through the years. Out of concern for player health and well-being, MLB and the MLB Players Association (MLBPA) worked together to create and implement an electronic medical record and Health and Injury Tracking System (HITS) for all MLB and Minor League Baseball (MiLB) players. Now active for over 5 seasons, this database has provided valuable, detailed reports regarding specific injuries occurring in professional baseball, such as hamstring strains and concussions.6,7

With shoulder and elbow injuries in pitchers representing the greatest proportion of DL assignments in recent years, a large body of literature on these injuries, particularly medial ulnar collateral ligament (MUCL) injuries, has been published.8-13 Since the initial description of MUCL reconstruction, or “Tommy John surgery,” by Dr. Frank Jobe in 1986, much has been done to improve the technique and rehabilitation to maximize player performance following surgery.10,14-16 Despite this increased attention, large-scale epidemiologic reporting of MUCL injuries in MLB is lacking, but such a report is desirable. The purpose of this work is to: 1) provide a large-scale analysis of injuries occurring in MLB baseball over the course of 18 seasons (1998-2015); 2) highlight the financial implications of these injuries; and 3) detail the evolution of MUCL injuries and reconstructive surgery since it was first performed on a MLB pitcher in 1974. Our study represents the largest longitudinal analysis of MLB injuries since the league expanded to its current level of 30 teams in 1998. It is our hope that this work will serve as a framework for future study of the most common and highest impact injuries occurring in baseball.

Materials And Methods

We performed a retrospective review of the MLB DL from 1998 to 2015. Data analyzed included player demographics such as club, year of placement, age, and position. Injury-specific variables included date of placement on DL, length of time on DL, date of reinstatement, body part injured, diagnosis, and cost of replacement. If a player was put on the DL multiple times during a season, each placement was viewed as a different injury, even if it was to the same body part. If a player was put on the DL for injuries to multiple body parts, the primary injury was analyzed.

Disabled List Data

Although the DL has existed since 1916, this current study covers 18 seasons from 1998 to 2015. The 1998 season was chosen as a starting point because this is the year when MLB expanded to 30 teams. Since then, the number of teams and the active roster limits (25 players) have remained constant, allowing for reliable comparisons across seasons. Initially designed as a roster management tool to allow injured players to temporarily be replaced with healthy players, the DL was not created as an injury database. However, the rules and regulations of the DL have remained fairly constant over the last 18 years, allowing reasonable comparisons of injury data and trends across this timespan. In order for a player to be assigned to the DL, the nature and extent of injury must be certified by a physician. Once designated for the DL, a player cannot return to the major league team for a minimum of 15 days. If the injury is severe, the player can remain on the DL for the remainder of the season or until he is deemed healthy enough to return to play by a physician. One notable exception is the treatment of concussions. Since 2011, a player diagnosed with a concussion may be placed on the DL for a minimum of 7 days rather than 15. The introduction of the HITS database in 2010 should allow for more detailed and reliable study of injuries in baseball moving forward. Although it contains robust data for every injury that has occurred in MLB and MiLB over the last 5 seasons, it does not allow for epidemiologic and longitudinal study of injury patterns and trends in baseball prior to 2010.


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