Ultrasonographic assessment of the ulnar collateral ligament and medial elbow laxity in college baseball players

Background: The prevalence of medial elbow instability is high in athletes who throw, such as baseball players. The aim of this study was to assess the medial aspect of the elbow with ultrasonography to detect changes in baseball players. Methods: Ultrasonography of the medial aspect of the elbow was performed, while gravity stress was applied with the elbow in 90degrees of flexion, on thirty college baseball players (twelve pitchers and eighteen fielders) to assess medial joint laxity and deformity of the Ulnar collateral ligament. The dominant (throwing) extremity was compared with the contralateral extremity. Clinical data were correlated with ultrasonographic findings. Results: The medial joint space was significantly wider on the throwing side than it was on the contralateral side (2.7 mm and 1.6 mm, respectively; p < 0.01), and the proximal part of the ulna was shifted significantly laterally on the throwing side (p < 0.01). Angular deformity of the ulnar collateral ligament was found in five subjects, and it was significantly associated with lateral shift of the proximal part of the ulna (p < 0.01). Medial elbow pain was associated with widening of the medial joint space (p < 0.05) and with the presence of angulation of the ulnar collateral ligament (p < 0.01). Conclusions: Medial elbow laxity and elbow valgus on the throwing side of baseball players were increased compared with those in nonplayers. Angular deformity of the ulnar collateral ligament suggests that the ligament bends over the distal-medial edge of the trochlea. Ultrasonography can provide useful information about the condition of the ulnar collateral ligament and about medial elbow laxity in athletes who throw.