title: Glenoid version by CT scan: an analysis of clinical measurement error and introduction of a protocol to reduce variability.
abstract: OBJECTIVE
  Recent studies have challenged the accuracy of conventional measurements of glenoid version. Variability in the orientation of the scapula from individual anatomical differences and patient positioning, combined with differences in observer measurement practices, have been identified as sources of variability. The purpose of this study was to explore the utility and reliability of clinically available software that allows manipulation of three-dimensional images in order to bridge the variance between clinical and anatomic version in a clinical setting.
  
  
  METHODS
  Twenty CT scans of normal glenoids of patients who had proximal humerus fractures were measured for version. Four reviewers first measured version in a conventional manner (clinical version), measurements were made again (anatomic version) after employing a protocol for reformatting the CT data to align the coronal and sagittal planes with the superior-inferior axis of the glenoid, and the scapular body, respectively.
  
  
  RESULTS
  The average value of clinical retroversion for all reviewers and all subjects was -1.4° (range, -16° to 21°), as compared to -3.2° (range, -21° to 6°) when measured from reformatted images. The mean difference between anatomical and clinical version was 1.9° ± 5.6° but ranged on individual measurements from -13° to 26°. In no instance did all four observers choose the same image slice from the sequence of images.
  
  
  CONCLUSIONS
  This study confirmed the variation in glenoid version dependent on scapular orientation previously identified in other studies using scapular models, and presents a clinically accessible protocol to correct for scapular orientation from the patient's CT data.
authors.affiliation: VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, Netherlands. f.vandebunt@vumc.nl.
authors.forename: Fabian
authors.initials: F
authors.lastname: van de Bunt
authors.affiliation: Kaiser Permanente, 4760 Sunset Blvd, Los Angeles, CA, 90027, USA. mlpearl@mac.com.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Pearl
authors.affiliation: Kaiser Permanente, 4760 Sunset Blvd, Los Angeles, CA, 90027, USA. eric.k.lee@nsmtp.kp.org.
authors.forename: Eric K
authors.initials: EK
authors.lastname: Lee
authors.affiliation: Kaiser Permanente, 4760 Sunset Blvd, Los Angeles, CA, 90027, USA. lauren.y.peng@nsmtp.kp.org.
authors.forename: Lauren
authors.initials: L
authors.lastname: Peng
authors.affiliation: Kaiser Permanente, 4760 Sunset Blvd, Los Angeles, CA, 90027, USA. paul.j.didomenico@nsmtp.kp.org.
authors.forename: Paul
authors.initials: P
authors.lastname: Didomenico
mesh_terms: D000368:Aged; D005260:Female; D061165:Glenoid Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015203:Reproducibility of Results; D012785:Shoulder Joint / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: 3D measurement; Glenoid; Glenoid version; Shoulder; Version; Version measurement