Imaging description

Stress fractures affect most frequently tibia and rarely fibula. When the fibula is involved, stress fractures affect the distal 1/3 and very rarely proximal 1/3. Radiographic findings of the stress fractures of the fibula may be identical to the stress fractures occurring to other common locations, which include a focal periosteal reaction (Figure 59.1), a focal cortical thickening, and a band of sclerosis. Focal cortical thickening may be associated with a lucent line (black line) perpendicular to the cortex. Longitudinal stress fractures are uncommon, usually occurring in the tibia. Radiography may show irregular cortical thickening and medullary sclerosis in a longitudinal fashion (Figure 59.2A). Axial images of CT (Figure 59.2B) demonstrate a cortical disruption (fracture) at multiple slices. Coronal images of CT and MRI (Figure 59.2C) or planer images of bone scan may better delineate its longitudinal extension.

Importance

Sensitivity of radiography for stress fractures is suboptimal. The diagnosis of stress fracture can be made clinically with pertinent clinical history even with negative radiographs. The diagnosis may be challenging with atypical clinical presentations, uncommon locations, and atypical imaging findings. Imaging findings may be misinterpreted as more aggressive lesions, particularly infection or tumor. Familiarity of these uncommon presentations of stress fractures is important to avoid unnecessary biopsy and to reach a correct diagnosis.