title: The medial-ridge sign as an indicator of anterior glenoid bone loss.
abstract: BACKGROUND
  The goal of this study was to investigate the incidence of a medial bony ridge at the scapular neck in patients with recurrent anterior shoulder instability and analyze its reliability in identifying anterior glenoid rim bone loss.
  
  
  METHODS
  A total of 109 shoulders in 105 consecutive patients underwent primary surgical stabilization for recurrent anterior shoulder instability with preoperative 2-dimensional and 3-dimensional computed tomography (CT) evaluation. The CT images of each affected shoulder were analyzed for the extent of anterior glenoid bone loss and the presence of a "medial-ridge sign." The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the medial-ridge sign were calculated for different sizes of glenoid rim defects.
  
  
  RESULTS
  A positive medial-ridge sign was detected in 77.1% of the shoulders. The sensitivity of the medial-ridge sign ranged from 81.6% (95% confidence interval [CI], 73.0%-87.9%) for defects greater than 0% to 100% (95% CI, 82.4%-100%) for defects ≥20%. The PPV of the medial-ridge sign decreased from 100% for defects >0% to 11.9% for defects ≥25%. The specificity of the medial-ridge sign decreased from 100% (95% CI, 61.0-100%) for defects >0%, to 25.3% (95% CI, 17.7%-34.6%) for defects ≥25%. The NPV of the medial-ridge sign increased from 24.0% for defects >0% to 100% for defects >20%.
  
  
  CONCLUSIONS
  The medial-ridge sign represents a CT-based radiologic sign with high sensitivity and NPV for identification of significant anterior glenoid rim defects in case of recurrent anterior shoulder instability.
authors.affiliation: Department of Traumatology and Sports Injuries, Paracelsus Medical University, Salzburg, Austria. Electronic address: philipp.moroder@pmu.ac.at.
authors.forename: Philipp
authors.initials: P
authors.lastname: Moroder
authors.forename: Mark
authors.initials: M
authors.lastname: Tauber
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoffelner
authors.forename: Lukas
authors.initials: L
authors.lastname: Ernstbrunner
authors.forename: Christoph
authors.initials: C
authors.lastname: Sattler
authors.forename: Alexander
authors.initials: A
authors.lastname: Auffarth
authors.forename: Herbert
authors.initials: H
authors.lastname: Resch
mesh_terms: D000328:Adult; D001862:Bone Resorption / Q000150:complications / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology*; D008297:Male; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012785:Shoulder Joint / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Diagnostic Study; Glenoid bone loss; Level II; glenoid defect; medial-ridge sign; shoulder dislocation; shoulder instability