title: Reliability of Magnetic Resonance Imaging Signs of Posterolateral Rotatory Instability of the Elbow.
abstract: OBJECTIVE
  To evaluate radiographic signs of posterolateral rotatory instability (PLRI) on magnetic resonance imaging (MRI). The goal was to establish objective radiographic criteria to aid in the diagnosis of PLRI.
  
  
  METHODS
  The MRI scans of 60 patients were evaluated retrospectively. Two study groups were compared. Group 1 (n = 30) consisted of unstable elbows in which PLRI was confirmed by clinical examination and arthroscopy. Group 2 (stable; n = 30) served as the control group. Patients in group 2 had transient epicondylitis without clinical suspicion of instability. Joint incongruity was analyzed for sagittal views through the radial head and the coronoid tip and for coronal and axial views. Interobserver and intra-observer reliability were evaluated.
  
  
  RESULTS
  In the sagittal view through the radial head, average radiocapitellar incongruity differed significantly between groups 1 and 2. In addition, mean ulnohumeral incongruity in an axial view through the motion axis of the distal humerus showed significant differences between groups. Sagittal views through the tip of the coronoid and coronal views did not reveal significant differences in patients with unstable elbows compared with the control group.
  
  
  CONCLUSIONS
  The current study provides useful MRI criteria indicative of PLRI when combined with physical examination. Cutoff points of 1.2 mm for radiocapitellar incongruity (sagittal view) and 0.7 mm for axial ulnohumeral incongruity (axial view) are suitable to screen for PLRI. Radiocapitellar incongruity greater than 2 mm and axial ulnohumeral incongruity greater than 1 mm are highly suspicious of elbow instability.
  
  
  METHODS
  Diagnostic IV.
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany. Electronic address: michael.hackl@uk-koeln.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Hackl
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.
authors.forename: Kilian
authors.initials: K
authors.lastname: Wegmann
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Ries
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Leschinger
authors.affiliation: Clinic for Shoulder Surgery, Bad Neustadt/Saale, Germany.
authors.forename: Klaus Josef
authors.initials: KJ
authors.lastname: Burkhart
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center, Cologne, Germany.
authors.forename: Lars Peter
authors.initials: LP
authors.lastname: Müller
mesh_terms: D000328:Adult; D000368:Aged; D001182:Arthroscopy; D003287:Contrast Media; D004551:Elbow Joint / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media
keywords: Elbow instability; MRI; PLRI; chronic instability; diagnosis