Kurokawa Daisuke, Yamamoto Nobuyuki, Ishikawa Hiroaki, Nagamoto Hideaki, Takahashi Hiroyuki, Muraki Takayuki, Tanaka Minoru, Sato Katsumi, Itoi Eiji
Department of Sports Medicine and Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan; Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
J Shoulder Elbow Surg. 2017 Jun;26(6):1083-1087. doi: 10.1016/j.jse.2016.11.051. Epub 2017 Jan 25.
The relationship between the disabled throwing shoulder and humeral retroversion has recently attracted a great deal of attention. However, none of the previous studies clarified when the side-to-side difference of humeral retroversion in young baseball players would start. This study aimed to clarify when the difference of humeral retroversion in the dominant and nondominant sides appeared in baseball players.
The bicipital-forearm angle in bilateral shoulders of 172 elementary school baseball players was measured by ultrasound. The bicipital-forearm angle was defined as an angle between the perpendicular line to the bicipital groove and the ulnar long axis with the elbow flexed at 90°. The correlation between the bicipital-forearm angle and the grade and the difference of the bicipital-forearm angle between the dominant and nondominant sides were analyzed.
In the nondominant shoulders, the bicipital-forearm angle increased with the grade in school (r = 0.32, P < .0001), but this was not observed in the dominant shoulders. In the fourth to sixth graders, the bicipital-forearm angles were significantly smaller in the dominant shoulders than in the nondominant shoulders.
Our findings indicated that humeral retroversion decreased with age in the nonthrowing side but not in the throwing side and that the side-to-side difference of humeral retroversion in the baseball players became obvious from the fourth grade. We assume that the repetitive throwing motion restricts the physiologic humeral derotation process and the difference became apparent from the fourth grade when the growth spurt begins in boys.
残疾投掷肩与肱骨后倾之间的关系最近备受关注。然而，以往的研究均未阐明年轻棒球运动员肱骨后倾的左右差异何时开始出现。本研究旨在明确棒球运动员优势侧和非优势侧肱骨后倾差异何时出现。
对172名小学棒球运动员双侧肩部的肱二头肌-前臂角进行超声测量。肱二头肌-前臂角定义为肱二头肌沟垂线与尺骨长轴之间的夹角，肘部屈曲90°。分析肱二头肌-前臂角与年级之间的相关性以及优势侧和非优势侧肱二头肌-前臂角的差异。
在非优势肩中，肱二头肌-前臂角随年级升高而增加（r = 0.32，P <.0001），但在优势肩中未观察到这种情况。在四至六年级学生中，优势肩的肱二头肌-前臂角明显小于非优势肩。
我们的研究结果表明，非投掷侧肱骨后倾随年龄增长而减小，而投掷侧则不然，并且棒球运动员肱骨后倾的左右差异从四年级开始变得明显。我们推测，重复性投掷动作会限制肱骨生理性旋后过程，而这种差异从四年级男孩开始进入生长突增期时变得明显。
