Surgery to replace a torn ulnar collateral ligament. The injury is common among baseball pitchers as a result of incorrect mechanics when throwing curveballs and sliders. The procedure is named after Tommy John, the first pitcher to successfully recover from it. The procedure generally involves taking a tendon from the opposite wrist or leg and grafting it in place of the torn UCL. Medical practice has advanced to the point where most pitchers who undergo this surgery can be pitching again within a year, and will be fully recovered within two years.