title: Accurate Measurement of Greater Tuberosity Displacement Without Computed Tomography: Validation of a Method on Plain Radiography to Guide Surgical Treatment.
abstract: BACKGROUND
  Residual displacement of greater tuberosity (GT) fractures has been shown to negatively affect shoulder function. However, accurate measurement of GT displacement remains a problem with errors up to 13 mm on plain radiography (XR). A new GT ratio for measuring fracture displacement on XR is described, validated, and correlated with computed tomography (CT) and surgical decision making.
  
  
  METHODS
  A retrospective review of shoulder radiographs was performed from 2007 to 2010 to identify all cases of isolated GT fractures with both XR and CT. The GT ratio was performed on all XR and correlated with superior GT displacement measured on CT. The GT ratio was then tested for accuracy of surgical decision using 5-mm superior displacement on CT as the cutoff. Finally, the inter- and intraobserver reliabilities of the GT ratio were calculated and compared with the Neer and Arbeitsgemeinschaft fur Osteosynthesefragen (AO) classifications.
  
  
  RESULTS
  Forty cases of acute GT fractures with XR and CT were identified. The GT ratio correlated very well with superior displacement on CT (Pearson correlation = 0.852, P < 0.01) and accurately classified GT fractures as "surgical" (n = 9, 23%) or "nonsurgical" (n = 31, 77%). GT ratios ≤0.00 were nonsurgical, ≥0.50 were surgical, and 0.00-0.50 warranted further imaging (P < 0.01). The GT ratio performed as well as or better than the AO and Neer classifications for inter- and intraobserver reliabilities.
  
  
  CONCLUSIONS
  The GT ratio described in this study correlates very well with CT for superior GT fracture displacement. It involves significantly less radiation and accurately classifies GT fractures as nonsurgical (ratio < 0.00), surgical (ratio > 0.50), or as benefiting from further imaging (0.00-0.50). It performs as well or better than the Neer or AO classification.
  
  
  METHODS
  Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: *Département de Recherche en Orthopédie, Hopital Sacre-Coeur de Montreal, Université de Montréal, Montréal, Québec, Canada; and †Département de Génie de la Production Automatisée, Centre Hospitalier de l'Universite de Montreal, École de Technologie Superieur, Montréal, Québec, Canada.
authors.forename: Jennifer A J
authors.initials: JA
authors.lastname: Mutch
authors.forename: Dominique M
authors.initials: DM
authors.lastname: Rouleau
authors.forename: G-Yves
authors.initials: GY
authors.lastname: Laflamme
authors.forename: Nicola
authors.initials: N
authors.lastname: Hagemeister
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012784:Shoulder Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed; D055815:Young Adult