### Instruction: What is a Tommy John Surgery?
### Input: Ulnar collateral ligament reconstruction, colloquially known as Tommy John surgery (TJS), is a surgical graft procedure where the ulnar collateral ligament in the medial elbow is replaced with either a tendon from elsewhere in the patient's body, or with one from a deceased donor. The procedure is common among collegiate and professional athletes in several sports, particularly in baseball.
### Response: A surgical graft procedure where the ulnar collateral ligament in the medial elbow is replaced with either a tendon from elsewhere in the patient's body, or with one from a deceased donor.