Virginia Research Day 2025

Medical Student Research Clinical

18 Forearm Flexor Strength as a Predictive Risk Factor for Ulnar Collateral Ligament Injury n Baseball Athletes

Tobias Addis, OMS-I, MPH 1 ; Andrew Hagen, OMS-I 1 ; David Redden, PhD 1 ; Nicole Fremarek, DO 1 ; Matthew Fury, MD 2 ; Albert Kozar, DO 1 ; Mark Rogers, DO 1 ; Per Gunnar Brolinson, DO 1 Corresponding author: ahagen@vt.vcom.edu

1 Edward Via College of Osteopathic Medicine - Virginia Campus 2 Baton Rouge Orthopaedic Clinic, Baton Rouge, LA

Medial elbow injuries, especially ulnar collateral ligament injuries, are prevalent among baseball pitchers and can have significant impacts on playability and associated costs with recovery. These injuries can be attributed to the large external valgus torque imposed on the medial elbow at maximum external rotation (MER) during a baseball pitch. Studies have shown that the external valgus torque experienced by the medial elbow during pitching can be compensated via functional stabilization from muscles and tendons in the forearm. However, limited research has examined the potential contribution of muscle strength imbalance towards the mechanism of medial elbow injury in baseball pitchers. A retrospective cohort study was conducted with data collected from baseball pitchers utilizing the FlexPro Grip device. The collected data consisted of force measured at fingertip, force measured at mid finger, and the ratio of the respective force measurements. These measurements were accurately obtained utilizing the FlexPro Grip device. The participants were divided into 2 cohorts: pitchers with medial elbow injury or pain (sprain, strain, tear, recent

surgical repair, or adjacent joint pain) and those with no medial elbow injury or pain that required rest from throwing. The participants of this study were de-identified. Statistical analysis was conducted utilizing RStudio, and the two-sample Mann-Whitney U (Wilcoxon Rank-Sum) test was selected for robustness to smaller samples. The Mann-Whitney U test was performed across the injured (n=18) cohort and the uninjured (n=28) cohort for the four-finger fingertip flexion measurements, the four-finger midfinger flexion measurements, and the midfinger/fingertip flexion ratio measurements. The analysis revealed significant p-values for the four finger midfinger flexion measurements (p<0.0001) and the midfinger/fingertip flexion ratios (p<0.0001), with a non-significant p-value for the four-finger fingertip flexion measurements (p=0.4507). Therefore, there is a statistically significant difference between the four-finger midfinger flexion strength measurements and the ratio of midfinger flexion strength to fingertip flexion strength of injured

and uninjured cohorts. The results of the statistical analysis suggest that there is a measurable correlation between midfinger flexion strength and pitching associated injuries in baseball pitchers. An underlying mechanism that may explain this phenomenon is that the relatively lower midfinger flexion strength in the injured cohort (x̄=133.33, uninjured x̄=163.17) indicates that the flexor digitorum superficialis is unable to provide as much muscular support to the humeroulnar joint and therefore places a higher strain on the ulnar collateral ligament. Further research on the topic at hand should aim to include larger samples and investigate the relationship between UCL injury and the strength of other muscles crossing the humeroulnar joint (pronator teres m., flexor carpi radialis m., palmaris longus m., flexor carpi ulnaris m., etc.). Furthermore, investigation of the protective benefit of strength-building exercise of these flexor muscles should be pursued to reduce the burden of UCL musculoskeletal injury in this population.

Approved by VCOM IRB, Protocol #2024-051.

143 2025 Research Recognition Day