[Special aspects of stress fractures].

Background: Stress fractures are very common in clinical practice. They can be classified into fatigue fractures that affect healthy bone and insufficiency fractures in which the bone is already damaged or weakened.

Imaging Modalities: Conventional x‑ray images are the standard method in case of a suspected stress fracture. If x‑rays are negative, magnetic resonance imaging (MRI) can be performed, which has a significantly higher sensitivity and can provide further information such as evidence for a pathological fracture. Computed tomography (CT) is suitable for an exact representation of the course of the fracture line and thus for preoperative planning. As a nuclear medicine procedure, bone scintigraphy can be used as bone metabolism in the area of a fracture is increased.

Key Imaging Findings: Typical x‑ray signs are the gray cortex sign, the periosteal reaction and a fracture line that is often oriented perpendicular to the cortex and which shows a parallel sclerotic line. Later on, callus material becomes evident. MRI reveals periosteal and medullary edema, a reaction in the surrounding soft tissue and a T1-hypointense fracture line. In CT, the fracture line is hypodense and often associated with an adjacent sclerotic area.

Conclusions: For a correct diagnosis, it is important to be familiar with the appropriate imaging modalities and the respective imaging findings of stress fractures. If initial x‑rays are normal and symptoms persist, an MRI should be performed. This is also to rule out other causes such as a pathological fracture.