Back on the Mound: Study Examines Return to Sport after Ulnar Collateral Ligament Surgery in MLB Pitchers

MLB pitchers who had ulnar collateral ligament (UCL) surgery threw harder with less use of the fastball, and they had superior overall pitching ability and strike-zone command than matched controls, according to new research presented at the AAOS 2025 Annual Meeting.

“UCL injury rates in baseball players have been rising to alarming levels, while the recent development of advanced analytics and pitch-tracking analysis is now driving player development and evaluation throughout the MLB,” said author Michael Andrew Mastroianni, MD, orthopaedic surgery resident at Columbia University Irving Medical Center/New York Presbyterian Hospital. “In order to push player health forward, it is critical to use this huge amount of public data to evaluate risk factors for injury. In this analysis, several advanced analytic and pitch-tracking pitching metrics used widely throughout the MLB were examined as potential risk factors for UCL surgery for the first time.”

The study was a retrospective analysis of return-to-play and performance data on 119 MLB pitchers who had primary UCL reconstruction or repair between April 2018 and November 2023. Their mean age was 26.8 years, and they played an average of 3.6 seasons. Furthermore, 74 percent of the pitchers were right-handed, and 42.6 percent were starters.

The researchers followed the players for three seasons after surgery. Analysis involved paired t-tests to compare metrics before and after surgery. Only 4 percent of the athletes returned to play 1 year after surgery, 79 percent at the two-season mark, and 99 percent during season three post-surgery. The mean length of time until return to play was 558 days.

From pre-injury season one to postoperative seasons one and two, the players had a significant decline in several metrics, including innings pitched, pitch count, and fWAR (Fangraphs’ calculation of wins above replacement, which measures a player’s value to the team). Other metrics were similar before and after, such as expected fielding independent pitching (known as xFIP) and skill-interactive earned run average (known as SIERA).

At two seasons postoperatively, pitchers maintained their Stuff+ (a measure of the physical characteristics of a pitch) but had worse Location+ (an assessment of a pitcher’s ability to put pitches in the right place) and Pitching+ (which uses the physical characteristics, location, and count of each pitch to assess the overall quality of the pitcher’s process).

At three seasons postoperatively, many pitchers returned to pre-injury performance in several metrics, including pitch count (63 percent), xFIP (61 percent), fWAR (53 percent), velocity (78 percent), fastball velocity (77 percent), horizontal movement (83 percent), vertical movement (72 percent), Stuff+ (73 percent), Location+ (89 percent), and Pitching+ (78 percent). However, overall, only 3 percent returned to full performance by season one, 21 percent by season two, and 32 percent by season three. The study did not identify any presurgical factors that could predict return to full performance.

The researchers are continuing to examine these metrics as risk factors for injury, as well as potential evaluations of return to performance after UCL surgery.

“Defining risk factors in terms players and teams (and fans!) understand helps to bridge the gap between the medical community and professional sports, so that we can better collaborate and use the data that are now available to advance player health and optimize performance,” Dr. Mastroianni said. “Ultimately, we hope this study … better informs players and teams on safe player-development protocols and trends throughout the league.”

Dr. Mastroianni’s coauthors of “Return to Performance Following UCL Surgery in Major League Baseball Pitchers” are Jennifer Alissa Kunes, BA; Dany Badawi El-Najjar, BS; Kyle Obana, MD; Sohil S. Desai, MD; Cole Richard Morrissette, BA, MA; Alexander Rondon, MD; Charles A. Popkin, MD, FAAOS; and Christopher S. Ahmad, MD, FAAOS.

Keightley Amen, BA, ELS, is a freelance writer for AAOS Now.