Major League Baseball Health and Injury Tracking System (HITS): A Review of MLB Injuries Documented in the HITS Database Since Its Inception

Abstract

Background: The Major League Baseball (MLB) Health and Injury Tracking System (HITS), created in 2010 with the MLB Players Association, was designed to overcome limitations of injured list-based reporting. It serves as a longitudinal injury surveillance platform and electronic medical record across major and minor league players.

Purpose: To evaluate all publications related to the HITS database to provide an overview of epidemiology, treatment outcomes, and return-to-play (RTP) rates in professional baseball, guiding player safety and performance strategies.

Study design: Scoping review; Level of evidence, 4.

Methods: All peer-reviewed publications utilizing the HITS database (2010-2023) were reviewed under PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Studies reporting epidemiology, surgical versus nonoperative management, and RTP outcomes across upper extremity, lower extremity, spine, and other injuries were synthesized.

Results: From 2011 to 2016, HITS recorded 49,955 injuries, resulting in 722,176 missed days of play. Pitchers accounted for 39% of injuries, with the upper extremity most affected (39%). Ulnar collateral ligament (UCL) injuries, while the sixth most common, represented the leading cause of surgery (46%) and season-ending injuries (60%). RTP following UCL reconstruction ranged from 73% to 84%, though outcomes declined with revision procedures. Shoulder injuries were also prevalent: labral repairs showed moderate RTP rates (74%-82%), whereas rotator cuff repair yielded poor outcomes (14%-42%), leading to preference for nonoperative care. Lower extremity injuries included hamstring strains, hip/groin injuries, and meniscal pathology, with variable RTP timelines. Core injuries, lumbar spine disorders, and concussions also contributed significantly to time lost. Overall, HITS has informed >40 publications, highlighting variable outcomes by injury type, treatment, and player position.

Conclusion: The HITS database provides the most comprehensive epidemiologic resource on injuries in professional baseball, identifying high-risk conditions and characterizing management outcomes. RTP success varies widely, with certain injuries such as UCL reconstruction yielding relatively favorable results, while others such as rotator cuff repair remain challenging.

Keywords: Health and Injury Tracking System (HITS); Major League Baseball (MLB); baseball; sports medicine; ulnar collateral ligament (UCL).