title: Computed tomography osteoabsorptiometry for assessing the density distribution of subchondral bone as a measure of long-term mechanical stress in the "rugby shoulder".
abstract: BACKGROUND
  Rugby is a collision sport with a high risk of shoulder injury. Although traumatic anterior shoulder instability is common, the long-term effects of rugby and joint instability on the shoulder have not been described; thus, this study assessed the effects of rugby itself, and joint instability, on the glenoid cavity.
  
  
  METHODS
  Both sides of the shoulders from 25 rugby players and 17 control patients with unilateral shoulder instability were prospectively evaluated by means of computed tomography osteoabsorptiometry, which represents the distribution of mineralization in subchondral bone plate (DMSB) as a marker of the long-term loading history of a joint. For the quantitative analysis, intergroup differences of maximum Hounsfield unit (HU) values in 7 areas on the glenoid were assessed in the uninjured intact shoulder to characterize the influence of rugby. Side-to-side differences of the HUs in each area were assessed in each participant to characterize the effects of shoulder instability. For the qualitative analysis, associations between the patterns of each DMSB and each group were assessed by means of correspondence analysis.
  
  
  RESULTS
  All examined areas on the glenoid had a significantly higher HUs in rugby players. Shoulder instability affected the HUs in both groups. A qualitative analysis demonstrated that the maximum HU tended to be shifted more inferiorly in rugby players and in the unstable shoulders.
  
  
  CONCLUSIONS
  Rugby affects the shoulder joint, regardless of any history of instability, suggesting that "rugby shoulder" tends to involve degenerative changes, such as osteoarthritis or labral tears.
authors.affiliation: Department of Orthopaedic Surgery, Juntendo University Faculty of Medicine, Bunkyo, Tokyo, Japan. k-saki@luck.ocn.ne.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Ryuji
authors.initials: R
authors.lastname: Sashi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Moriya
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kaketa
authors.forename: Hideo
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Itoigawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kaneko
mesh_terms: D000293:Adolescent; D000328:Adult; D002113:Calcification, Physiologic / Q000502:physiology*; D005260:Female; D005538:Football / Q000293:injuries*; D061165:Glenoid Cavity; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007593:Joint Instability / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D012785:Shoulder Joint / Q000473:pathology* / Q000502:physiology / Q000503:physiopathology; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D055815:Young Adult