Daisuke Kurokawa1, Nobuyuki Yamamoto2, Hiroaki Ishikawa3, Hideaki Nagamoto4, Hiroyuki Takahashi5, Takayuki Muraki4, Minoru Tanaka6, Katsumi Sato6, Eiji Itoi7. 1. Department of Sports Medicine and Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan; Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan. 2. Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan. 3. Department of Physical Medicine and Rehabilitation, Tohoku University School of Medicine, Sendai, Japan. 4. Department of Orthopaedic Surgery, Kurihara Central Hospital, Kurihara, Miyagi, Japan. 5. Department of Orthopaedic Surgery, Kesen-numa City Hospital, Kesen-numa, Miyagi, Japan. 6. Department of Sports Medicine and Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan. 7. Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan. Electronic address: itoi-eiji@med.tohoku.ac.jp.
Abstract
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
Authors: Ralf J Doyscher; Leopold Rühl; Benjamin Czichy; Konrad Neumann; Timm Denecke; Bernd Wolfarth; Scott A Rodeo; Markus Scheibel Journal: Arch Orthop Trauma Surg Date: 2022-08-18 Impact factor: 2.928