The "gray cortex ": an early sign of stress fracture.

The purpose of this report is to describe an early radiographic sign of stress fracture, the "gray cortex ". The imaging findings in three patients with tibial stress fractures were reviewed. The "gray cortex " sign was evident on the initial conventional radiographs in all three cases. It was prospectively reported as a sign of stress fracture in two patients and was evident on the initial radiographs (taken elsewhere) of the third patient, who was referred for additional workup of a possible neoplasm. Special imaging studies (technetium-99m bone scan, computed tomography, and magnetic resonance imaging) confirmed the diagnosis in all three cases.