title: Association between acromioclavicular joint pain and capsular bulging in adolescent baseball players.
abstract: OBJECTIVE
  The purpose of this study was to investigate the association between acromioclavicular (AC) joint pain and superior capsular bulging assessed by ultrasound in adolescent baseball players.
  
  
  METHODS
  One hundred and fifty players (1st-8th graders) were examined. All subjects underwent physical examinations, including assessment of tenderness on the AC joint and provocative tests (the Buchberger's test and the cross-body adduction stress test). Bilateral AC joints with the arm in both the resting and the cross-body positions were examined by ultrasound.
  
  
  RESULTS
  Twelve of 150 players (8 %) had AC symptoms with both positive tenderness and positive provocative tests. Interestingly, their prevalence increased with age-one of the 70 (1.4 %) 1st-3rd graders, six of 46 (13 %) 4th-6th graders and five of 34 (15 %) 7th-8th graders. Ultrasonography of AC joints in the cross-body position showed that the difference in superior capsular bulging between the throwing and non-throwing sides was significantly greater in symptomatic players (1.6 ± 1.2 mm) than in asymptomatic players (0.2 ± 0.8 mm) (p = 0.002).
  
  
  CONCLUSIONS
  The prevalence of superior capsular bulging was significantly higher in adolescent baseball players with AC joint pain than in those without it. In adolescent baseball players with shoulder pain, AC joint symptoms should be considered amongst potential causes. Careful observation of these patients is suggested in cases of superior capsular bulging of the AC joint as determined by ultrasonography.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan. hat@ortho.med.tohoku.ac.jp.
authors.forename: Taku
authors.initials: T
authors.lastname: Hatta
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sano
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagamoto
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kurokawa
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takahashi
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, Sendai Red Cross Hospital, Sendai, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Koike
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, 980-8574, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000173:Acromioclavicular Joint / Q000000981:diagnostic imaging* / Q000293:injuries; D000293:Adolescent; D018771:Arthralgia / Q000000981:diagnostic imaging / Q000453:epidemiology; D001484:Baseball / Q000293:injuries*; D002648:Child; D006801:Humans; D017746:Joint Capsule / Q000000981:diagnostic imaging*; D007592:Joint Diseases / Q000000981:diagnostic imaging / Q000453:epidemiology*; D008297:Male; D010808:Physical Examination; D011187:Posture; D015995:Prevalence; D016059:Range of Motion, Articular; D020069:Shoulder Pain / Q000000981:diagnostic imaging / Q000453:epidemiology*
keywords: Acromioclavicular joint; Baseball; Capsular bulging; Sports injury; Throwing; Ultrasonography