title: Radiographic Analysis of the Hill-Sachs Lesion in Anteroinferior Shoulder Instability After First-Time Dislocations.
abstract: To identify the relation between the Hill-Sachs (H-S) angle and arm position at the time of the initial dislocation, and to see if this correlates with the glenoid track.
  
  
  
  A total of 102 patients (89 male patients, 87.2%), with a mean age of 32 years (range, 17 to 38 years), were divided into 2 groups, abduction (ABD) and adduction (ADD), dependent on the position of the arm at the time of the instability event. All patients were evaluated with bilateral computed tomography scans (3-dimensional) to define the H-S position on the glenoid track and to measure the H-S angle. One-way analysis of variance was used to compare the H-S angle between the 2 groups.
  
  
  
  Dislocation occurred in ABD in 45 patients (44.1%) and in ADD in 57 (55.9%). The H-S angle was 32.4° ± 4.7° in the ABD group versus 16.1° ± 2.9° in the ADD group. All patients' injuries were "on-track" glenoid injuries in both groups.
  
  
  
  This study identified a difference in the H-S angle relative to arm position at the time of initial dislocation. Patients whose injury occurred in the ABD position showed a higher H-S angle, leading to an increased risk of engagement, because the long axis of the H-S lesion is parallel to the glenoid in a position of function. Thus arm position at the time of the initial instability event may be a risk factor for engagement and higher risk of recurrence. LEVEL OF
  
  
  
  Level IV, prognostic case series.
authors.affiliation: Department of Orthopaedic Surgery, Concordia Hospital for Special Surgery, Rome, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Giacomo
authors.affiliation: Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, U.S.A.
authors.forename: Petar
authors.initials: P
authors.lastname: Golijanin
authors.affiliation: Sports Medicine Service, Massachusetts General Hospital, Boston, Massachusetts, U.S.A.
authors.forename: George
authors.initials: G
authors.lastname: Sanchez
authors.affiliation: Sports Medicine Service, Massachusetts General Hospital, Boston, Massachusetts, U.S.A.. Electronic address: MattProvencher@gmail.com.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Provencher
mesh_terms: D000293:Adolescent; D000328:Adult; D000070896:Bankart Lesions / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000000981:diagnostic imaging*; D008297:Male; D011379:Prognosis; D012008:Recurrence; D012189:Retrospective Studies; D012540:Scapula / Q000000981:diagnostic imaging; D012783:Shoulder Dislocation / Q000000981:diagnostic imaging*; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult