Paper 17: Decreased Glenohumeral External Rotation is associated with Elbow Injury in Adolescent Baseball Pitchers
Authors: Banffy Michael , Uquillas Carlos , Haselman William , Karnyski Steven 
Published: August 2023

Objectives: To compare bilateral standard glenohumeral range of motion, humeral torsion & humeral torsion-corrected glenohumeral range of motion within and between healthy adolescent baseball pitchers & adolescent baseball pitchers who have an injury to the throwing elbow. Secondarily, to analyze the relationship between humeral torsion angle and glenohumeral rotational motion in adolescent pitchers. Methods: Baseball pitchers aged 13-17 were prospectively enrolled into either a healthy group, if currently pitching in the community without complaint or injured group, if they presented to clinic for an elbow injury related to pitching. Bilateral standard glenohumeral internal & external rotation was measured in degrees using a bubble goniometer with the scapulothoracic joint manually stabilized. Bilateral humeral torsion angles were measured using an Ultrasound & bubble goniometer and were used to calculate humeral torsion-corrected glenohumeral range of motion. Parametric tests were used to compare values within and between groups for both the dominant and non-dominant extremities with significance defined as p<0.05. Pearson’s correlation was used to evaluate the relationship between humeral torsion and standard glenohumeral motion in each group. Results: Twenty-nine healthy and twenty-five injured pitchers were enrolled with no difference in age or hand dominance between groups. The dominant shoulder of both the healthy (Table 2) and injured (Table 3) groups demonstrated a significant increase in humeral retrotorsion with increased standard glenohumeral external rotation & GIRD. However, no difference in humeral torsion-corrected range of motion was present within groups. Injured pitchers displayed less standard & humeral torsion-corrected external rotation of the dominant shoulder as well as less standard external rotation of the non-dominant shoulder compared to the healthy pitchers (Table 4). No difference in internal rotation measurements or humeral torsion was found between groups. A moderate correlation was found between ipsilateral humeral torsion angle and standard glenohumeral external (r=0.49) & internal rotation (r=-0.58) in the dominant shoulder of healthy pitchers (Figure 1) but no correlation (r< 0.3) was found between these measures in the dominant shoulder of injured pitchers. Conclusions: Both healthy & injured adolescent baseball pitchers displayed dominant shoulder GIRD, external rotation gain & retrotorsion of the humerus. In healthy pitchers, dominant glenohumeral motion was correlated to the humeral torsion angle suggesting that the osseous adaptation of humerus significantly contributed to these findings. However, this correlation was not found in the injured pitchers, suggesting that soft tissue factors played a larger role in the development of GIRD & external rotation gain in this group. Additionally, injured pitchers displayed less standard glenohumeral external rotation of both shoulders and less humeral torsion-corrected external rotation of the dominant shoulder compared to healthy pitchers. This suggests a baseline difference in the soft tissue and/or structure of the pitchers’ shoulders between groups. Glenohumeral internal rotation and humeral retrotorsion were not associated with injury status in our study. Clinically, this study suggests that rehabilitation programs including modalities to improve external rotation may be of benefit for adolescent baseball pitchers with elbow injuries & further research on the structural variations of the adolescent pitching shoulder is needed. [Table: see text][Table: see text][Table: see text]