Assessing UCL Width during Valgus Load for College Baseball Pitchers using Ultrasound Imaging

Abstract

Injuries to the Ulnar Collateral Ligament (UCL) of the elbow are common in overhead throwing athletes. A repetitive valgus force during the throwing motion places significant stress on the UCL. More research needs to be conducted to investigate new methods to assess potential thickening of the anterior bundle of the UCL in order to understand ligament changes that may occur throughout the season. PURPOSE: To examine the reliability of ultrasound imaging measurements of UCL width at 2 different anatomical locations using 5Nm valgus stress; and to determine if a difference in ligament width exists between the two measurements 4 weeks apart within the season. METHODS: Thirteen Division I college men’s baseball pitchers participated with a mean age of 20.4 ± 1.45 SD) and body mass index (BMI) 24.56 ± 1.78 SD). Ultrasound images were obtained of the anterior band of the UCL on the participant’s throwing arm using a GE LOGIQ E ultrasound unit with a linear probe at 12Mhz. Participants were placed in a supine position with a wedge placed underneath their forearm to maintain their elbow position at a 30 deg. flexion angle. A 5 Nm valgus stress was applied 20 centimeters distal to the medial epicondyle. Measurements at the mid substance and the apex of the trochlea were taken at the beginning of the baseball season and then again 4 weeks later. Three images were measured during each session. RESULTS: Intra-rater reliability as expressed by ICC (3, 3) was .929 (SEM= 0.18mm) & .935 (SEM= 0.20mm) for the apex of trochlea measurement site and .861 (SEM= 0.22mm) & .920 (SEM=0.16mm) for the mid-substance measurement site, indicating excellent intra-rater reliability. There was no difference between the measurements obtained on the two testing dates (Apex of trochlea mean width 2.90mm & 2.92mm; t= -.155; p ≥ 0.05) and (Mid-substance mean width 4.49 mm & 4.44 mm; t= .571; p ≥ 0.05) CONCLUSIONS: Excellent intra-rater reliability was found at all four measurement sites. There was no significant difference in UCL width from the beginning of the season and one-month into the season. Further research is recommended to perform multiple imaging sessions throughout the year to determine the long term physiological effects of overhead throwing on the anterior band of the UCL and to study the connection between UCL width changes, tissue quality, and injury risk.