Grey cortex sign (stress fracture)

Last revised by Matt Skalski on 31 Dec 2021

The grey cortex sign was described as an early sign of stress (fatigue) fractures on plain radiographs and refers to subtle ill-definition/lucency of the cortex at the site of microfracture. However, plain radiography is insensitive (~25%, range 15-25%) for the detection of early-stage injuries. CT is much more sensitive for the detection of bone loss that precedes true fracture 1, however, MRI is the most sensitive/specific modality for the diagnosis of fatigue fractures 4.

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