The
ulnar collateral ligament (UCL) can become stretched, frayed, or torn through the repetitive stress of the throwing motion. The risk of injury to the UCL is believed to be extremely high, This injury is associated with baseball, although it sometimes appears in other sports. Compared to athletes who play other sports, baseball pitchers are at elevated risk of
overuse injuries and injuries caused by early sports specialization among children and teenagers. The results of a 2002 study suggest that the total number of pitches thrown is the greatest determinant. The study examined the throwing volume, pitch type and throwing mechanics of 426 pitchers aged nine to fourteen for one year. Compared to pitchers who threw 200 or fewer pitches in a season, those who threw 201–400, 401–600, 601–800, and 800+ pitches faced an increased risk of 63%, 181%, 234%, and 161% respectively. The types of pitches thrown showed a smaller effect; throwing a
slider was associated with an 86% increased chance of elbow injury while throwing a
curveball was associated with an increase in pain. There was only a weak correlation between throwing mechanics perceived as bad and injury-prone. Pitchers may require a second procedure after recovering from a first surgery. From 1999 to 2015, 39 major league pitchers had a "revision" – a second Tommy John surgery, with an average of about 5 years between the first and second surgeries. The need for a second UCL reconstruction in major league pitchers is an important factor in the duration of their contracts. == Risks ==