In a study examining case definition for atypical femoral fractures (AFF), where sensitivity and specificity of radiographic fracture characteristics were calculated, lateral cortex transverse fracture pattern was the most sensitive and specific characteristic and the most highly agreed upon by reviewers. Radiographs from 55 physician-confirmed AFFs and a sample of 39 non-AFFs were evaluated by 4 independent expert reviewers representing 4 medical specialties. Reviewers indicated the presence or absence of the following characteristics viewable on radiograph: fracture pattern, comminution, periosteal and/or endosteal thickening, and cortical thickening. They found:

• The most sensitive factors distinguishing AFF from non-AFF were lateral cortex transverse fracture pattern (mean 93.6 %), medial cortex transverse or oblique fracture pattern (mean 84.1 %), and minimal/non-comminution (mean 93.2 %).
• Specificity was the greatest for lateral cortex transverse fracture pattern (mean 95.5 %).