title: The cortical irregularity in the transition zone of the radial head and neck: a reliable radiographic sign of an occult radial head fracture.
abstract: OBJECTIVE
  Exclusion or detection of non-displaced radial head fractures can be difficult in radiographs, because they might lack conclusive radiographic signs, such as fracture lines or distracted articular fragments. Based on the typical injury mechanism of a radial head fracture, causing the head to hit the capitulum and leading to a depression of the anterolateral border of the radial head, we hypothesized that even slight cortical irregularities in the transition zone of the radial neck and head result from that depression and may be a reliable radiographic sign of an underlying radial head fracture. Secondarily, we tested the null hypothesis that the lack of cortical irregularities is sufficient to exclude a fracture of the radial head.
  
  
  METHODS
  84 patients with sets of anteroposterior and lateral radiographs of the elbow were identified from the database of a level 1 trauma center and divided into 2 groups. Group A was formed out of 42 patients with non-displaced radial head fractures, group B out of 42 patients without a history of previous elbow trauma, whose medical history also contained radiographic images. After the radial head was blackened, the transition zone of the radial neck and head was assessed by two attending orthopedic surgeons for presence of a cortical irregularity. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of cortical irregularity were calculated for the assessment of radial head fractures. The kappa measure of agreement was utilized to evaluate interrater agreement.
  
  
  RESULTS
  The specificity was 87.80 and 97.56 %, respectively, its sensitivity 86.04 and 75.61 %. A high NPV (85.71 %; 80.00 %) and PPV (96.88 %; 88.10 %.) were observed. The interrater agreement for the proposed diagnostic method was high, with a Cohen kappa score of 0.737 (p < 0.001).
  
  
  CONCLUSIONS
  A cortical irregularity in the transition zone of the radial neck and head seems to be a reliable radiographic sign of an underlying radial head fracture. The absence of the cortical irregularity can be used to correctly identify a non-fractured radial head.
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center of Cologne, Kerpenerstr. 62, 50937, Cologne, Germany. tim.leschinger@uk-koeln.de.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Cologne, Germany. tim.leschinger@uk-koeln.de.
authors.forename: Tim
authors.initials: T
authors.lastname: Leschinger
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center of Cologne, Kerpenerstr. 62, 50937, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Cologne, Germany.
authors.forename: Lars Peter
authors.initials: LP
authors.lastname: Müller
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center of Cologne, Kerpenerstr. 62, 50937, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Cologne, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hackl
authors.affiliation: Center for Orthopedic and Trauma Surgery, University Medical Center of Cologne, Kerpenerstr. 62, 50937, Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, Cologne, Germany.
authors.forename: Kilian
authors.initials: K
authors.lastname: Wegmann
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D000071538:Cortical Bone / Q000000981:diagnostic imaging* / Q000293:injuries; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011884:Radius / Q000000981:diagnostic imaging*; D011885:Radius Fractures / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D055815:Young Adult
keywords: Cortical irregularity; Diagnosis; Occult; Radial head fracture; Reliable radiographic sign; Transition zone