title: Three-dimensional computed tomography scan evaluation of the pattern of erosion in type B glenoids.
abstract: BACKGROUND
  Type B glenoids according to Walch are subclassified into a group with no posterior erosion (B1) and a group with important posterior erosion (B2) based on 2-dimensional axial computed tomography (CT) scan images. Three-dimensional (3D) CT scan reconstruction seems to improve the accuracy of the measurement of erosion because of its independence from positional errors. The aim is to quantify the direction and amount of posterior erosion of type B glenoids using a reproducible 3D measuring technique.
  
  
  METHODS
  We performed 3D reconstruction of 72 type B glenoids (24 type B1 glenoids and 48 type B2 glenoids) using Mimics (Materialise, Haasrode, Belgium). The native glenoid plane and intermediate glenoid plane were determined by use of 3-Matic (Materialise). The normal glenoid version, eroded retroversion, and difference in retroversion were measured. Next, the maximum erosion and its orientation were quantified.
  
  
  RESULTS
  There was always minimum erosion of 1.7 mm, and the mean erosion was 4.2 mm. There was a significant difference between the mean erosion in type B1 glenoids (3.5 mm) and type B2 glenoids (4.5 mm) (P = .019). The mean orientation of the erosion was mostly to the posteroinferior side (119°; SD, 26.8). There was a significant difference between the mean orientation in type B1 glenoids (132°; SD, 25.2) and type B2 glenoids (113°; SD, 25.5) (P = .004).
  
  
  CONCLUSIONS
  With the use of this newly developed reproducible measuring technique, the maximum erosion in type B glenoids can be adequately quantified. All glenoids showed signs of important erosion. Because the orientation of the maximum erosion in type B1 glenoids is situated more inferiorly, the 2-dimensional CT scan technique can be insufficient to evaluate this erosion.
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Gent University Hospital, Gent, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Beuckelaers
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Gent University Hospital, Gent, Belgium.
authors.forename: Matthijs
authors.initials: M
authors.lastname: Jacxsens
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Gent University Hospital, Gent, Belgium.
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Tongel
authors.affiliation: Department of Orthopedic Surgery and Traumatology, Gent University Hospital, Gent, Belgium. Electronic address: lieven.dewilde@Ugent.be.
authors.forename: Lieven F
authors.initials: LF
authors.lastname: De Wilde
mesh_terms: D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000145:classification / Q000000981:diagnostic imaging*; D012540:Scapula / Q000000981:diagnostic imaging*; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
keywords: 3D CT scan; 3D reconstruction; Anatomic Study; Basic Science Study; Imaging; biconcave glenoid; omarthrosis; type B glenoid