title: Measurement of the Glenoid Track In Vivo as Investigated by 3-Dimensional Motion Analysis Using Open MRI.
abstract: BACKGROUND
  A Hill-Sachs lesion is a common injury associated with anterior glenohumeral instability, and a Hill-Sachs lesion that engages with the anterior glenoid rim is 1 factor related to recurrent instability. In a cadaveric study in 2007, a new concept, the "glenoid track," was proposed to evaluate the risk of engagement of Hill-Sachs lesions with the glenoid.
  
  
  OBJECTIVE
  To investigate the glenoid track in vivo using a custom-developed noninvasive motion analysis system.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Using a wide-gantry magnetic resonance imaging (MRI) scanner, the right shoulders of 30 healthy volunteers were examined. The MRI scans were taken of the right arm in 7 static supine positions from 0° to maximum abduction, keeping maximum external rotation and horizontal extension. Using the custom motion analysis system, 3-dimensional models of the scapula and humerus were created from the MRI data. Then, the movement of the humerus and scapula was calculated using voxel-based registration of each model, and the motion of the glenoid on the humeral head was analyzed.
  
  
  RESULTS
  The models demonstrated that glenoid contact shifted from the inferomedial to the superolateral portion of the humeral head. The mean widths of the glenoid track with the arm at 60°, 90°, 120°, and 150° of abduction were 20.7 ± 4.5 mm, 19.4 ± 3.9 mm, 18.9 ± 2.7 mm, and 18.7 ± 2.5 mm (89%, 83%, 82%, and 81% of the glenoid width), respectively. The width of the glenoid track at 60° of abduction was significantly greater than those at 90°, 120°, and 150° of abduction (P = .0472, .0148, and .0083, respectively). There were no significant differences among widths measured at 90°, 120°, and 150° of abduction.
  
  
  CONCLUSIONS
  The existence and widths of the glenoid track were confirmed in vivo.
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Koishi
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Futai
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Goto
authors.affiliation: Department of Orthopaedic Biomaterial Science, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan itoi-eiji@med.tohoku.ac.jp.
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005260:Female; D061165:Glenoid Cavity / Q000033:anatomy & histology* / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D006811:Humerus / Q000033:anatomy & histology / Q000502:physiology; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement / Q000502:physiology*; D012540:Scapula / Q000033:anatomy & histology / Q000502:physiology; D012785:Shoulder Joint / Q000033:anatomy & histology* / Q000502:physiology
keywords: 3D motion analysis; Hill-Sachs lesion; MRI; anterior shoulder instability; engaging Hill-Sachs lesion; glenoid track; in vivo; off-track Hill-Sachs lesion; on-track Hill-Sachs lesion