From the Guidelines
Magnetic Resonance Imaging (MRI) is the recommended imaging modality for diagnosing stress fractures when they are not visible on X-rays. This recommendation is based on the most recent and highest quality study available, which suggests that MRI should supersede bone scintigraphy as the imaging examination of choice for suspected stress fracture when radiographs are negative 1.
Key Points to Consider
- MRI is highly sensitive for detecting bone marrow edema, which is an early sign of stress injury before a fracture line develops.
- MRI can identify stress fractures within 24-72 hours of symptom onset, whereas X-rays may not show changes for 2-3 weeks or may never reveal certain stress fractures.
- MRI provides detailed visualization of both bone and surrounding soft tissues, allowing clinicians to assess the severity of the fracture and identify any associated soft tissue injuries.
- Bone scans (nuclear scintigraphy) are an alternative but less specific option, as they can detect areas of increased bone turnover but cannot distinguish between stress fractures and other conditions like infection or tumors.
- CT scans may be useful for certain locations like the navicular bone or hip, but MRI remains superior for most stress fractures due to its ability to detect early bone stress reactions and provide multiplanar images without radiation exposure.
Clinical Decision Making
When deciding on the best imaging modality for diagnosing stress fractures, it is essential to consider the patient's symptoms, medical history, and the location of the suspected fracture. According to the American College of Radiology (ACR) Appropriateness Criteria, MRI is the preferred imaging modality for diagnosing stress fractures in the lower extremities, excluding the pelvis and hip 1. In cases where the radiograph is negative, MRI without IV contrast is usually appropriate as the next imaging study 1.
Evidence-Based Practice
The recommendation to use MRI as the primary imaging modality for diagnosing stress fractures is supported by multiple studies, including a 2024 update of the ACR Appropriateness Criteria 1. These studies highlight the importance of using cross-sectional imaging, such as MRI, to diagnose stress fractures, especially when radiographs are negative. By prioritizing MRI, clinicians can provide accurate diagnoses and develop effective treatment plans to improve patient outcomes.
From the Research
Imaging Modalities for Stress Fractures
If a stress fracture is not visible on an X-ray, several imaging modalities can be used to diagnose it. These include:
- Magnetic Resonance Imaging (MRI): MRI is highly sensitive and can provide further information such as evidence for a pathological fracture 2, 3, 4, 5, 6.
- Computed Tomography (CT): CT is suitable for an exact representation of the course of the fracture line and thus for preoperative planning 2, 4, 5, 6.
- Bone Scintigraphy: Bone scintigraphy can be used as a nuclear medicine procedure to detect increased bone metabolism in the area of a fracture 2, 4, 5.
- Ultrasonography: Ultrasonography can provide a limited evaluation of the superficial osseous structures, but its use is limited in diagnosing stress fractures 4, 5.
- Dual Energy Computed Tomography (DECT) and Magnetic Resonance Bone Imaging (MR Bone): These new techniques may become increasingly important for the correct diagnosis of stress fractures in the future 6.
Recommendations for Imaging
The recommended approach is to start with conventional X-ray images, and if the results are negative, proceed with MRI, which is the gold standard for diagnosing stress fractures 2, 3, 4, 5, 6. CT can be used if the MRI findings are unclear or if more detailed information about the fracture line is needed 2, 6.