title: 3D CT assessment of the relationship between humeral head alignment and glenoid retroversion in glenohumeral osteoarthritis.
abstract: BACKGROUND
  Glenoid bone loss associated with advanced glenohumeral arthritis is frequently accompanied by subluxation of the humeral head with subsequent inferior outcomes of shoulder arthroplasty. We hypothesized that the relationship between the center of the humeral head and the perpendicular to the glenoid fossa plane differs from, and is independent of, the relationship between the center of the humeral head and the plane of the scapula.
  
  
  METHODS
  Three-dimensional computed tomography (3D CT) imaging was performed on sixty patients with advanced osteoarthritis and fifteen controls with no osteoarthritis to define the baseline relationship between the center of the humeral head and the perpendicular to the glenoid fossa plane and the plane of the scapula. Correlations between these variables and the amount of bone loss and glenoid version were assessed.
  
  
  RESULTS
  There was a strong linear relationship (p &lt; 0.001) between glenoid retroversion and the center of the humeral head in relation to the center line of the scapula (humeral-scapular alignment). Humeral head alignment in relation to the glenoid plane (humeral-glenoid alignment) was variable and not strongly correlated with the amount of glenoid retroversion. The average glenoid retroversion for the normal shoulders was -3.5°, and the average humeral-scapular alignment offset percentage was -2.3%. The average humeral-glenoid alignment offset for the normal shoulders was 0.5 mm with an average humeral-glenoid alignment offset percentage of 0.9%.
  
  
  CONCLUSIONS
  The location of the humeral head in relation to the glenoid can be defined as displacement from the plane of the scapula and from the perpendicular of the glenoid plane. These two measures are independent of one another. The data suggest that each measurement may represent a different effect on glenoid loading.
  
  
  CONCLUSIONS
  The importance of this study is that it presents quantitative data and clear guidelines to define two measurements of glenohumeral alignment as separate and important variables. The clinical relevance of these methods will be further defined when they are correlated with clinical outcomes.
authors.affiliation: Department of Orthopaedic Surgery, Michigan State University/Kalamazoo Center of Medical Studies, 1000 Oakland Drive, Kalamazoo, MI 49008. E-mail address: sabes001@gmail.com.
authors.forename: Vani J
authors.initials: VJ
authors.lastname: Sabesan
authors.affiliation: College of Human Medicine, Michigan State University, 321 Michigan Place N.E., Grand Rapids, MI 49503.
authors.forename: Mark
authors.initials: M
authors.lastname: Callanan
authors.affiliation: Orthopaedic and Rheumatologic Institute, Cleveland Clinic Main Campus, 9500 Euclid Avenue, Cleveland, OH 44195.
authors.forename: Ari
authors.initials: A
authors.lastname: Youderian
authors.affiliation: Orthopaedic and Rheumatologic Institute, Cleveland Clinic Main Campus, 9500 Euclid Avenue, Cleveland, OH 44195.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Iannotti
mesh_terms: D001862:Bone Resorption / Q000000981:diagnostic imaging; D060751:Bone Retroversion / Q000000981:diagnostic imaging*; D061165:Glenoid Cavity / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging* / Q000503:physiopathology; D021621:Imaging, Three-Dimensional; D010003:Osteoarthritis / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D012540:Scapula / Q000000981:diagnostic imaging / Q000503:physiopathology; D012785:Shoulder Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D014057:Tomography, X-Ray Computed