Factors Related to Increased Ulnar Collateral Ligament Thickness on Stress Sonography of the Elbow in Asymptomatic Youth and Adolescent Baseball Pitchers.
BACKGROUND
Stress ultrasound (SUS) of the elbow has demonstrated changes in the anterior band of the ulnar collateral ligament (UCL) in professional and high school-aged pitchers. However, there have been no large reports correlating pitching history data with SUS changes in youth and adolescent baseball pitchers.


HYPOTHESIS
Changes of the UCL on SUS will correlate with pitching volume in youth and adolescent baseball pitchers.


STUDY DESIGN
Cross-sectional study; Level of evidence, 3.


METHODS
SUS of the elbow was performed in both elbows of 102 youth and adolescent baseball pitchers. UCL thickness and the width of the ulnohumeral joint, at rest and with 150 N of valgus stress, were measured using a standardized, instrumented device. Demographic data, arm measurements, and a pitching history questionnaire were recorded as well. The pitchers were separated into 2 groups based on age: group 1 (12-14 years) and group 2 (15-18 years). SUS findings of the dominant elbows were compared between the 2 groups. Correlation analysis and linear regression were used to identify relationships between SUS findings and pitching history data.


RESULTS
In all pitchers, the mean UCL thickness was 4.40 mm in the dominant elbow and 4.11 mm in the nondominant elbow (P =.03). There was no significant difference between elbows in any joint space characteristics. A comparison of group 1 versus group 2 demonstrated significant differences in UCL thickness (4.13 vs 4.96 mm; P < .001), resting joint space width (6.56 vs 4.04 mm; P < .001), and stressed joint space width (7.68 vs 4.07 mm; P < .001). There was no difference in the change in joint space width between the 2 groups (1.11 vs 0.76 mm; P = .05). The UCL was significantly thicker in pitchers who threw more than 67 pitches per appearance (4.69 vs 4.14 mm), who pitched more than 5 innings per appearance (4.76 vs 4.11 mm), and who had more than 5.5 years of pitching experience (4.71 vs 4.07 mm; P < .001). Linear regression demonstrated that age, weight, and pitches per appearance (R 2 = 0.114, 0.370, and 0.326, respectively) significantly correlated with UCL thickness.


CONCLUSION
These findings suggest that UCL thickness increases as pitchers get older and heavier and as they increase their pitch volumes.
['Atanda|Alfred|A|', 'Averill|Lauren W|LW|', 'Wallace|Maegen|M|', 'Niiler|Tim A|TA|', 'Nazarian|Levon N|LN|', 'Ciccotti|Michael G|MG|']
D000293:Adolescent D001484:Baseball D002648:Child D000070637:Collateral Ligament, Ulnar D003430:Cross-Sectional Studies D004551:Elbow Joint D006801:Humans D016014:Linear Models D008297:Male D012146:Rest D014463:Ultrasonography
ulnar collateral ligament baseball stress ultrasound youth pitchers