AOSSM/AANA Specialty Day 2020-The Ulnar Collateral Ligament Responds to Stress in Professional Pitchers

The Ulnar Collateral Ligament Responds to Stress in Professional Pitchers

Pdf Summary

This prospective ultrasonographic study investigated how the ulnar collateral ligament (UCL) of professional baseball pitchers responds to pitching-related stress over time. The study enrolled 94 pitchers during Spring Training 2018, with follow-up ultrasounds performed at the end of the 2018 season and again in Spring Training 2019, totaling 107 pitchers with complete data.<br /><br />Key cohort characteristics included an average age of 23-24 years, approximately 6 years of pitching experience, and a peak fastball velocity near 95 mph. Notably, 22% had undergone UCL reconstruction (UCLR) surgery prior to or during the study period.<br /><br />Ultrasound measurements evaluated UCL thickness and valgus laxity (joint gapping under stress). Reliability of the measurements was good, with intraclass correlation coefficients (ICCs) ranging from 0.74-0.88. Results showed that higher pitching velocity and prior UCLR were significantly associated with greater UCL thickness at season start (p = 0.031 and 0.024, respectively).<br /><br />Longitudinally, UCL thickness increased over the course of the season and decreased during the off-season, reflecting ligament adaptation to repetitive stress and subsequent rest. Similarly, valgus laxity increased during the season and lessened in the off-season, further supporting ligament remodeling dynamics. Statistical modeling showed significant seasonal changes with notable effects of velocity and prior surgery on ligament characteristics.<br /><br />In conclusion, pitching stress induces measurable biological changes in the UCL, causing it to both thicken and lengthen over the competitive season. These findings confirm the UCL’s capacity for structural adaptation in response to mechanical load and recovery, highlighting its dynamic nature in professional pitchers.

Keywords

ultrasonographic study

ulnar collateral ligament

UCL

professional baseball pitchers

pitching-related stress

UCL thickness

valgus laxity

UCL reconstruction surgery

ligament adaptation

pitching velocity