title: Comparison of 3-Dimensional Computed Tomography-Based Measurement of Glenoid Bone Loss With Arthroscopic Defect Size Estimation in Patients With Anterior Shoulder Instability.
abstract: OBJECTIVE
  The purpose of this study was to compare four 3-dimensional (3D) computed tomography (CT) methods of measuring glenoid bone loss with the arthroscopic estimation of glenoid bone loss.
  
  
  METHODS
  Twenty patients with recurrent anterior shoulder instability underwent bilateral shoulder CT scans and were found to have glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed in all patients. Three-dimensional CT reconstruction was performed on the CT scans of each patient. The glenoid bone loss of each patient was measured using the surface area, Pico, ratio, and anteroposterior distance-from-bare area methods. The mean percent loss calculated with each method was compared with arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss.
  
  
  RESULTS
  The mean percent bone loss calculated with arthroscopic estimation, surface area, Pico, ratio, and anteroposterior distance-from-bare area methods was 18.13% ± 11.81%, 12.15% ± 8.50% (P = .005), 12.77% ± 8.17% (P = .002), 9.50% ± 8.74% (P < .001), and 12.44% ± 10.68% (P = .001), respectively. Repeated-measures analysis of variance showed that the 3D CT methods and arthroscopy were significantly different (F4,76 = 13.168, P = .02). The estimate using arthroscopy is 55% greater than the average of the 3D CT methods.
  
  
  CONCLUSIONS
  Our findings suggest that arthroscopy significantly overestimates glenoid bone loss compared with CT and call into question its validity as a method of measurement. A more internally consistent and accurate method for the measurement of glenoid bone loss is necessary to appropriately diagnose and treat shoulder instability.
  
  
  METHODS
  Level IV, case series.
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, U.S.A.
authors.forename: Neil K
authors.initials: NK
authors.lastname: Bakshi
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, U.S.A.
authors.forename: Ishan
authors.initials: I
authors.lastname: Patel
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, U.S.A.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Jacobson
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Debski
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan, U.S.A.. Electronic address: sekiya@med.umich.edu.
authors.forename: Jon K
authors.initials: JK
authors.lastname: Sekiya
mesh_terms: D000293:Adolescent; D000328:Adult; D001182:Arthroscopy / Q000379:methods*; D001847:Bone Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012540:Scapula / Q000000981:diagnostic imaging; D012782:Shoulder / Q000000981:diagnostic imaging; D012783:Shoulder Dislocation / Q000601:surgery; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult