title: The three-dimensional glenohumeral subluxation index in primary osteoarthritis of the shoulder.
abstract: BACKGROUND
  Assessment of glenohumeral subluxation is essential in preoperative planning of total shoulder arthroplasty. The purpose of this study was to evaluate a 3-dimensional (3D) glenohumeral subluxation index (GHSI) in shoulders with primary osteoarthritis (OA) and its relationship with morbid glenoid retroversion.
  
  
  METHODS
  The 3D computed tomography reconstructions of 120 healthy shoulders and 110 shoulders with primary glenohumeral arthritis (OA group), classified according to Walch's glenoid morphology, were analyzed. The 3D GHSI was assessed by measuring posterior decentering of the humeral head in relation to the native glenoid in each subject, and its correlation to morbid glenoid version was calculated.
  
  
  RESULTS
  The reproducible 3D GHSI (intraclass correlation coefficients ≥ 0.842) showed a posterior decentering of the humeral head in the OA population and in each type of glenoid morphology (P ≤ .005). A moderate correlation was observed in the OA group (r = -0.542; P < .001), but weak linear relationships were found for different glenoid morphology types (r between 0.041 and -0.307). Type A shoulders (r = -0.375; P = .006) correlated better than type B shoulders (r =  -0.217; P = .104). After shoulders were subcategorized according to a threshold for 3D subluxation, the posteriorly subluxated group increased its correlation (r = -0.438; P < .001), whereas the centered shoulders still exhibited no relationship (r = -0.192; P = .329).
  
  
  CONCLUSIONS
  Posterior humeral head decentering in relation to the native glenoid is present in each glenoid morphology type. Grouping measures according to morphology type and 3D subluxation showed at best moderate correlations between morbid version and 3D GHSI.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium; Department of Orthopaedic Surgery and Traumatology, University Hospital of Basel, Basel, Switzerland. Electronic address: matthijs.jacxsens@gmail.com.
authors.forename: Matthijs
authors.initials: M
authors.lastname: Jacxsens
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Tongel
authors.affiliation: Department of Orthopaedics, Orthopaedic Research Laboratory, University of Utah, Salt Lake City, UT, USA.
authors.forename: Heath B
authors.initials: HB
authors.lastname: Henninger
authors.affiliation: Department of Orthopaedics, Orthopaedic Research Laboratory, University of Utah, Salt Lake City, UT, USA.
authors.forename: Robert Z
authors.initials: RZ
authors.lastname: Tashjian
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: De Wilde
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D010003:Osteoarthritis / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012783:Shoulder Dislocation / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
keywords: 3D CT reconstruction; glenohumeral relationship; glenohumeral subluxation; glenoid morphology; glenoid version; humeral head subluxation; humeral head translation; total shoulder arthroplasty