title: Evaluation of the thickness of the medial ulnar collateral ligament in junior high and high school baseball players.
abstract: BACKGROUND
  Thickening of the medial ulnar collateral ligament in the throwing arm of adult baseball players is a well-known phenomenon. However, onset of the thickening is unclear among young baseball players. The purpose of this study was to evaluate the thickness of the medial ulnar collateral ligament in junior high and high school baseball players.
  
  
  METHODS
  Seventy-one uninjured and asymptomatic junior high and high school baseball players were included in the study. Participants underwent physical examination after completing a questionnaire, followed by ultrasonographic evaluation. The thickness of the medial ulnar collateral ligament was measured bilaterally. The thickness of the throwing and non-throwing sides in high school and junior high school baseball players, and within each group, was compared and statistically analyzed.
  
  
  RESULTS
  The medial ulnar collateral ligament in the throwing arm of high school baseball players was thicker than that in the non-throwing arm (5.5 vs. 4.4 mm), although no significant difference was seen in junior high school baseball players. High school baseball players showed a significantly thicker medial ulnar collateral ligament in the throwing arm than junior high school baseball players.
  
  
  CONCLUSIONS
  Thickening of the medial ulnar collateral ligament in the throwing arm of asymptomatic and uninjured baseball players may begin by the time the players reach high school.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aobaku, Sendai, 980-8574, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagamoto
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aobaku, Sendai, 980-8574, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Surgery, Sendai Medical Center, Sendai, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kurokawa
authors.affiliation: Department of Orthopaedic Surgery, Kesennuma City Hospital, Kesennuma, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Department of Physical Medicine and Rehabilitation, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Muraki
authors.affiliation: Department of Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Orthopaedic Surgery, Japan Red Cross Sendai Hospital, Sendai, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Koike
authors.affiliation: Department of Orthopaedic Surgery, Sendai City Hospital, Sendai, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sano
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aobaku, Sendai, 980-8574, Japan. itoi-eiji@med.tohoku.ac.jp.
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000293:Adolescent; D001484:Baseball; D017885:Collateral Ligaments / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D004551:Elbow Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D014463:Ultrasonography
keywords: Asymptomatic; Elbow; Medial ulnar collateral ligament; Ultrasonography; Valgus stress; Youth baseball players