Although ultrasonography has been used to assess medial elbow laxity, its usefulness has not yet been confirmed.


The aim of this study were to assess medial elbow laxity in high school baseball players based on measurements of the medial joint space (MJS) of the elbow using ultrasonography and radiography and to investigate the correlation between these assessments.


Thirty-two high school baseball players participated in this study. Fourteen players (44%) were diagnosed with Ulnar Collateral Ligament (UCL) injury. Valgus stress was applied to the elbow by gravity during ultrasonographic and radiographic assessments, and the MJS was measured. The MJS of the throwing side was compared with that of the non-throwing side, and the increase in the MJS of the throwing side was determined. The correlation between ultrasonographic and radiographic assessments was investigated and the usefulness of these assessments for the diagnosis of UCL injury was evaluated.


A moderate correlation was found between the ultrasonographic and radiographic assessments of the MJS of the throwing side (correlation coefficient=0.547, P=0.0009). Furthermore, a weak correlation was found for the increase in MJS (correlation coefficient=0.348, P=0.0505), although it was not significant. The comparisons of the radiographic assessments between the UCL injury and non-UCL injury groups showed a significant difference in both the MJS of the throwing side (P=0.0068) and the increase in the MJS (P=0.02), although no difference was found using ultrasonography.


Ultrasonography, similar to radiography, is useful for assessing medial elbow laxity. While radiography is useful for diagnosing UCL injury.

Keywords: Ultrasonography, Radiography, Elbow, Gravity, Laxity, Baseball.
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