Forearm Flexor Injuries in Major League Baseball Players: Epidemiology, Performance, and Associated Injuries

OBJECTIVES: The flexor-pronator mass provides dynamic support to the valgus stresses in the throwing elbow and is protective to the ulnar collateral ligament (UCL). Despite evidence highlighting the importance of the forearm flexor muscles in baseball pitching, no studies have reported the epidemiology, return to play, or associated injuries in elite baseball players. The purpose of this study examine the incidence, treatment, and outcomes of forearm flexor injuries in both Major and Minor League Baseball pitchers. METHODS: Injury data attributed to forearm flexor injury in Major League Baseball (MLB) and minor league teams was reviewed from 2010 to 2014. This included the numbers of players, seasonal timing of injury, days of competition missed, pre and post-injury performance data, and subsequent elbow surgery. Performance data collected consisted of ERA (earned run average), WHIP (walks plus hits per innings pitched), walks, strikeouts, and percent strikes. RESULTS: In MLB, 134 forearm flexor injuries occurred with a mean player age of 28.6 years and 111 (82.8%) were pitchers. In the minor leagues, 629 injuries occurred with a mean age of 22.8 years where 494 (78.5%) were pitchers. The highest percentage of injuries occurred in the month of July in both MLB (17.2%) and the minor leagues (17%). The median time spent on the disabled list (DL) for MLB players was 42 days (mean 128.1) compared to 28 days (mean 105.7) in the minor leagues. Of the players in MLB who sustained a forearm injury, subsequent injuries included 50 shoulder (37.3%), 48 elbow (35.8%), and 24 forearm (17.9%) injuries. Over the study period, 26 (19.4%) MLB and 56 minor league players (8.9%) required UCL reconstruction within 365 days of sustaining a forearm injury. Performance declined in virtually all categories in the season leading to the injury when compared to the previous season (n = 75) and significant differences were present in walks plus hits per inning pitched (WHIP) (from 1.24 to 1.34, P = 0.04) and strike percentage (63% to 62%, P = 0.036). CONCLUSION: Flexor-pronator injuries are responsible for considerable time on the DL in elite pitchers. Injury may be preceded with declines in performance and be associated with subsequent injuries to the shoulder and elbow.