Major league baseball (MLB) is one of the most popular sports in the United States, with an average annual viewership of 11 million for the All-Star game and almost 14 million for the World Series.1 MLB has an average annual revenue of almost $10 billion, while the net worth of all 30 MLB teams combined is estimated at $36 billion; an increase of 48% from 1 year ago.2 As the sport continues to grow in popularity and receives more social media coverage, several issues, specifically injuries to its players, have come to the forefront of the news. Injuries to MLB players, specifically pitchers, have become a significant concern in recent years. The active and extended rosters in MLB include 750 and 1200 athletes, respectively, with approximately 360 active spots taken up by pitchers.3 Hence, MLB employs a large number of elite athletes within its organization. It is important to understand not only what injuries are occurring in these athletes, but also how these injuries may be prevented.
Epidemiology
Injuries to MLB players, specifically pitchers, have increased over the past several years.4 Between 2005 and 2008, there was an overall increase of 37% in total number of injuries, with more injuries occurring in pitchers than any other position.5 While position players are more likely to sustain an injury to the lower extremity, pitchers are more likely to sustain an injury to the upper extremity.5 The month with the most injuries to MLB players was April, while the fewest number of injuries occurred in September.5 One injury that has been in the spotlight due to its dramatically increasing incidence is tear of the ulnar collateral ligament (UCL). Several studies have shown that the number of pitchers undergoing ulnar collateral ligament reconstruction (UCLR), commonly known as Tommy John surgery, has significantly increased over the past 20 years (Figure 1).4,6 Between 25% to 33% of all MLB pitchers have undergone UCLR.
While the number of primary UCLR in MLB pitchers has become a significant concern, an even more pressing concern is the number of pitchers undergoing revision UCLR, as this number has increased over the past several years.7 Currently, there is some debate as to how to best address the UCL during primary UCLR (graft type, exposure, treatment of the ulnar nerve, and graft fixation methods) because no study has shown one fixation method or graft type to be superior to others. Similarly, no study has definitively proven how to best manage the ulnar nerve (transpose in all patients, only transpose if preoperative symptoms of numbness/tingling, subluxation, etc. exist). Unfortunately, the results following revision UCLR are inferior to those following primary UCLR.4,7,8 Hence, given this information, it is imperative to both determine and implement strategies aimed at minimizing the need for revision.
Risk Factors for Injury
Although MLB has received more media attention than lower levels of baseball competition, there is relatively sparse evidence surrounding injury risk factors among MLB players. The majority of studies performed have evaluated risk factors for injury in younger baseball athletes (adolescent, high school, and college). The number of athletes at these lower levels sustaining injuries has increased over the past several years as well.9 Several large prospective studies have evaluated risk factors for shoulder and elbow injuries in adolescent baseball players. The risk factors include pitching year-round, pitching more than 100 innings per year, high pitch counts, pitching for multiple teams, geography, pitching on consecutive days, pitching while fatigued, breaking pitches, higher elbow valgus torque, pitching with higher velocity, pitching with supraspinatus weakness, and pitching with a glenohumeral internal rotation deficit (GIRD).10-17 The large majority of these risk factors are essentially part of a pitcher’s cumulative work, which consists of number of games pitched, total pitches thrown, total innings pitched, innings pitched per game, and pitches thrown per game. One prior study has evaluated cumulative work as a predictor for injury in MLB pitchers.18 While there were several issues with the study methodology, the authors found no correlation between a MLB pitcher’s cumulative work and risk for injury.
Given our current understanding of repetitive microtrauma as the pathophysiology behind these injuries, it remains unclear why cumulative work would be predictive of injury in youth pitchers but not in MLB pitchers.16 Several potential reasons exist as to why cumulative work may relate to risk of injury in youth pitchers and not MLB pitchers. Achieving MLB status may infer the element of natural selection based on technique and talent that supersedes the effect of “cumulative trauma” in many players. In MLB pitchers, cumulative work is closely monitored. In addition, these players are only playing for a single team and are not pitching competitively year-round, while many youth players play for multiple teams and may pitch year-round. To combat youth injuries, MLB Pitch Smart has developed recommendations on pitch counts and days of rest for pitchers of all age groups (Table).19 While data do not yet exist to clearly demonstrate the effectiveness of these guidelines, given the risk factors previously mentioned, it seems that these recommendations will show some reduction in youth injuries in years to come.
