Early Anatomic Changes of the Ulnar Collateral Ligament Identified by Stress Ultrasound of the Elbow in Young Professional Baseball Pitchers

Abstract

Background: Stress ultrasound (SUS) of the elbow has demonstrated changes in the anterior band of the ulnar collateral ligament (UCL) in professional baseball pitchers. However, there have been no reports documenting the chronological appearance of these changes.

Purpose: To characterize the chronology of anatomic changes of the UCL in a cohort of young professional baseball pitchers.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: SUS of the elbow was performed on the dominant arm in 127 asymptomatic professional pitchers aged 17 to 21 years. UCL thickness was measured at rest. The width of the ulnohumeral joint was measured at 30° of elbow flexion, both at rest and with 150 N of valgus stress, using a standardized instrumented device. Any ligament heterogeneity and calcifications were documented. Players were divided into 3 groups based on the number of years of professional experience before the ultrasound examination: 0 years (n = 51), 1-2 years (n = 54), and 3-4 years (n = 22). Additionally, players were divided into 5 groups based on chronological age at the time of the first SUS examination: 17 years (n = 5), 18 years (n = 18), 19 years (n = 33), 20 years (n = 20), and 21 years (n = 51). Statistically significant differences between the groups were determined.

Results: The mean UCL thickness was 5.85 ± 1.22 mm, 6.23 ± 1.32 mm, and 6.94 ± 2.12 mm in the players with 0, 1-2, and 3-4 years of professional experience, respectively. This difference was statistically significant overall (P = .024) as well as statistically significant between each consecutive group. There was no statistically significant difference in joint space width at rest or with applied stress between groups (P = .944). Additionally, there was no statistically significant difference in the presence of calcifications (27.5%, 27.8%, and 40.9%, respectively; P = .144) or heterogeneity (29.4%, 16.7%, and 40.9%, respectively; P = .502) as years of professional experience increased from 0 to 3-4 years. There were no significant differences in UCL thickness (P = .363), joint space width with stress (P = .648), or echotextural abnormalities based on chronological age (P = .871 [hypoechoic foci] and P = .520 [calcifications]).

Conclusion: These findings suggest that an increase in UCL thickness may be one of the first changes to develop in young professional baseball pitchers.

Keywords: asymptomatic pitchers; baseball; stress ultrasound of the elbow; ulnar collateral ligament.