title: Variations in normal sternoclavicular joints; a retrospective study to quantify SCJ asymmetry.
abstract: OBJECTIVE
  A wide degree of normal anatomical variation can occur at the sternoclavicular joint (SCJ). On occasion, this has led to concern for a pathological process, potentially resulting in a costly work-up, unnecessary patient worry and invasive diagnostic procedures such as biopsy. The purpose of this study was to determine the normal range of anatomical variation at sternoclavicular joints.
  
  
  METHODS
  One hundred four consecutive patients with chest CT done at our institution were selected. Patients with clear SCJ pathology, chest wall abnormality, CT slice thickness greater than 5 mm and sternotomy wires, were excluded. Chart review was done and showed no SCJ symptoms/signs. We measured the SCJ space, maximum clavicular head diameter within the joint and the distance from manubrium to the anterior margin of the clavicular head.
  
  
  RESULTS
  Left and right SCJ space ranged from 0.2 to 1.37 cm. The difference (delta or asymmetry) between left SCJ space and right SCJ space ranged from 0 (symmetrical) to 0.57 cm in 104 cases. Left and right clavicular head diameter ranged from 1.2 to 3.7 cm with left/right asymmetry (delta) ranging from 0 (symmetrical) to 1 cm. Manubrium to anterior margin of clavicular head ranged from 0.1 to 2.13 cm with delta ranging from 0 to 0.8 cm. Thirty-three patients demonstrated gas in the joint, five had poor articulation and four had calcification in the joint.
  
  
  CONCLUSIONS
  Greater than 10% of patients show substantial asymmetry in the sternoclavicular joints, which may be misinterpreted as pathological. Gas in the joint is a common phenomenon therefore should not be an indication for further work-up in asymptomatic patients and likely excludes the presence of effusion.
authors.affiliation: Emory Orthopaedics and Spine Center, Atlanta, NE 30329, USA.
authors.forename: Daymen
authors.initials: D
authors.lastname: Tuscano
authors.forename: Sima
authors.initials: S
authors.lastname: Banerjee
authors.forename: Michael R
authors.initials: MR
authors.lastname: Terk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013247:Sternoclavicular Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult