title: Association between scapula bony morphology and snapping scapula syndrome.
abstract: OBJECTIVE
  Scapular incongruity has been described as a contributing factor to the development of snapping scapula syndrome (SSS). The purpose of this retrospective case-control study was to determine the association between scapula bony morphology on magnetic resonance imaging (MRI) and the diagnosis of SSS.
  
  
  METHODS
  Bony morphologies of the scapula were evaluated on MRI scans of 26 patients with SSS and 19 patients with non-SSS pathologies. The medial scapula corpus angle (MSCA) was measured on axial MRI sequences. Scapulae were categorized as straight, S shaped, or concave. Two independent observers performed the measurements. Interobserver and intraobserver agreements of MSCA measurements were determined with intraclass correlation coefficients.
  
  
  RESULTS
  Axial scapula bony morphology identified 28 scapulae of the straight type, 14 S-shaped scapulae, and 5 concave scapulae. All 5 concave scapulae had confirmed SSS. Measurement of the MSCA showed excellent interobserver agreement of 0.80 (95% confidence interval [CI], 0.67 to 0.89) and intraobserver agreement of 0.70 (95% CI, 0.52 to 0.82). There were significant differences in the mean MSCAs between shoulders with SSS (14.4° ± 19.3°) and non-SSS shoulders (-3.3° ± 15.3°, P = .001). The odds ratio was 8.4 (95% CI, 2.2 to 31.8) for positive MSCA and SSS. The scapulothoracic distance was significantly decreased in the SSS group (14.9 ± 5.8 mm) compared with the non-SSS patients (24.0 ± 6.7 mm, P < .001).
  
  
  CONCLUSIONS
  Anterior angulation of the medial scapula in the axial plane was associated with SSS. Patients with a concave-shaped scapula and a positive MSCA have a 12-fold increased risk of SSS. The MSCA may prove helpful in determining the location and amount of scapular resection needed for patients with SSS.
authors.affiliation: Steadman Philippon Research Institute, Vail, CO, USA; The Steadman Clinic, Vail, CO, USA.
authors.forename: Ulrich J
authors.initials: UJ
authors.lastname: Spiegl
authors.affiliation: Steadman Philippon Research Institute, Vail, CO, USA; The Steadman Clinic, Vail, CO, USA.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Petri
authors.affiliation: Steadman Philippon Research Institute, Vail, CO, USA.
authors.forename: Sean W
authors.initials: SW
authors.lastname: Smith
authors.affiliation: Steadman Philippon Research Institute, Vail, CO, USA; The Steadman Clinic, Vail, CO, USA.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Ho
authors.affiliation: Steadman Philippon Research Institute, Vail, CO, USA; The Steadman Clinic, Vail, CO, USA. Electronic address: drmillett@thesteadmanclinic.com.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Millett
mesh_terms: D000293:Adolescent; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D059352:Musculoskeletal Pain / Q000175:diagnosis / Q000601:surgery*; D010027:Osteotomy / Q000379:methods*; D012189:Retrospective Studies; D012540:Scapula / Q000473:pathology* / Q000601:surgery; D013577:Syndrome; D055815:Young Adult
keywords: Snapping scapula syndrome; medial scapula corpus angle; partial scapulectomy; scapula bony morphology