title: 3-D CT is the most reliable imaging modality when quantifying glenoid bone loss.
abstract: BACKGROUND
  Posttraumatic anterior shoulder instability is associated with anterior glenoid bone loss, contributing to recurrence. Accurate preoperative quantification of bone loss is paramount to avoid failure of a soft tissue stabilization procedure as bone reconstruction is recommended for glenoid defects greater than 20% to 27%.
  
  
  OBJECTIVE
  We determined whether radiography, MRI, or CT was most reliable to quantify glenoid bone loss in recurrent anterior shoulder instability.
  
  
  METHODS
  Seven intact fresh-frozen human cadaveric shoulders were imaged with radiography, MRI, CT, and three-dimensional (3-D) CT. Three sequential anterior glenoid defects then were created, measured, and the shoulders reimaged after each defect. Defect sizes were less than 12%, 12% to 25%, and 25% to 40%. The gold standard measurement was determined by comparing measurements taken on the cadaver by two surgeons using digital calipers with the measurements determined by using electronic digital calipers on the 3-D CT. This measurement was used for comparison of all estimations by the evaluators. Twelve independent blinded evaluators reviewed the 112 image sets and estimated the percent of glenoid bone loss. Images were scrambled and rereviewed by the same observers 2 months later to determine intraobserver reliability. We determined reliability with kappa values.
  
  
  RESULTS
  Kappa values between predicted bone loss versus true loss (determined by our gold standard measurements) across all 12 raters for each modality were: 3-D CT, 0.50; CT, 0.40; MRI, 0.27; and radiographs, 0.15. Interobserver agreement (kappa) values were: 3-D CT, 0.54; CT, 0.47; MRI, 0.31; and radiographs, 0.15. The intraobserver agreement (kappa) values were: 3-D CT, 0.59; CT, 0.64; MRI, 0.51; and radiographs, 0.45.
  
  
  CONCLUSIONS
  Three-dimensional CT was the most reliable imaging modality for predicting glenoid bone loss. Regular CT was the second most reliable and reproducible modality.
authors.affiliation: Department of Orthopaedics, The Ohio State University Medical Center, The Ohio State University, 2050 Kenny Road, Suite 3300, Columbus, OH 43221, USA. julie.bishop@osumc.edu
authors.forename: Julie Y
authors.initials: JY
authors.lastname: Bishop
authors.forename: Grant L
authors.initials: GL
authors.lastname: Jones
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rerko
authors.forename: Chris
authors.initials: C
authors.lastname: Donaldson
mesh_terms: D001862:Bone Resorption / Q000000981:diagnostic imaging* / Q000473:pathology; D002102:Cadaver; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000473:pathology; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012540:Scapula / Q000000981:diagnostic imaging / Q000473:pathology; D012785:Shoulder Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*