The differences of humeral torsion angle and the glenohumeral rotation angles between young right-handed and left-handed pitchers

The differences between young right-handed and left-handed baseball players are not well known. This study compared the range of the shoulder motion and humeral torsion angle (HTA) between right-handed and left-handed young baseball pitchers. A total of 65 young baseball pitchers (age, 9-12 years; 46 right-handed throwers, R group; and 19 left-handed throwers, L group) were analyzed. The glenohumeral internal rotation (IR) angle and external rotation (ER) angle were measured at 90° shoulder abduction, and HTA was assessed using indirect ultrasonographic techniques. The side-to-side difference in HTA (d-HTA), glenohumeral ER difference (GERD), and glenohumeral IR deficit (GIRD) were calculated. The adjusted GIRD and adjusted GERD were defined as the angles obtained by subtracting d-HTA from GIRD and GERD, respectively, to exclude the influence of humeral retrotorsion difference. HTA and ER of the throwing limb were significantly greater than those of the nonthrowing limb in the R group (HTA: 84° vs. 77°; P