From the Guidelines
Spaced X-rays are recommended over MRI for diagnosing a suspected Salter-Harris fracture of the distal fibular physis in a 14-year-old male with a right lateral ankle injury, as they provide adequate visualization of potential physeal widening while being less costly and more readily available. In this case, with tenderness to palpation over the lateral malleolus and possible ligament involvement (ATFL and CFL), spaced X-rays are the appropriate first-line imaging study, as they can effectively demonstrate displacement that might be missed on standard views 1.
Key Considerations
- The Ottawa Ankle Rules (OAR) are the current standard clinical imaging guidelines to determine if radiographs are necessary, and they have been shown to have a high sensitivity for detecting ankle fractures 1.
- Weight-bearing radiographs, if possible, provide important information, particularly with fractures of uncertain stability, and can help confirm stability with a medial clear space of <4 mm 1.
- While an MRI would offer superior soft tissue detail and could detect bone marrow edema, it is typically reserved for cases where X-rays are inconclusive or when there is concern for significant ligamentous injury that would alter management 1.
- For pediatric ankle injuries with suspected growth plate involvement, stress or weight-bearing X-rays taken from multiple angles can effectively demonstrate displacement that might be missed on standard views.
Imaging Options
- Spaced X-rays: provide adequate visualization of potential physeal widening, less costly, and more readily available.
- MRI: offers superior soft tissue detail, but is typically reserved for cases where X-rays are inconclusive or when there is concern for significant ligamentous injury.
- CT scans: expose the patient to more radiation than X-rays and are not necessary for most Salter-Harris fractures, particularly type I injuries which often show only physeal widening.
Clinical Decision Making
- If the spaced X-rays are negative but clinical suspicion remains high, or if symptoms persist despite appropriate treatment, then an MRI could be considered as a second-line imaging option.
- The decision to use MRI or other imaging modalities should be based on the clinical presentation and the need for further evaluation, rather than as a first-line imaging study 1.
From the Research
Diagnosis of Salter-Harris Fracture
- Spaced x-rays are recommended over Magnetic Resonance Imaging (MRI) for diagnosing a suspected Salter-Harris fracture of the distal fibular physis in a 14-year-old male with a right lateral ankle injury 2.
- The use of spaced x-rays allows for the detection of occult fractures, which may not be visible on initial radiographs 2.
- A study found that 18% of children with acute ankle injuries and normal initial radiographs showed evidence of periosteal new bone formation on follow-up radiographs, implying the presence of an occult fracture 2.
Assessment of Displacement and Damage
- Spaced x-rays can help assess displacement and damage to the Anterior Talofibular Ligament (ATFL) and Calcaneofibular Ligament (CFL) by detecting changes in the alignment of the distal fibula and the presence of any fractures or avulsions 3, 4.
- A systematic review found that the most common injuries of the pediatric ankle are ATFL sprains and osteochondral avulsions, rather than Salter-Harris type I fractures 4.
- MRI can be useful in detecting ligamentous lesions, bone contusions, and joint effusions, but may not be necessary for diagnosing Salter-Harris fractures 5, 4.
Treatment and Management
- The treatment of Salter-Harris fractures depends on the severity of the displacement and the presence of any associated injuries 3, 6.
- Closed reduction and casting may be sufficient for non-displaced or minimally displaced fractures, while open reduction and internal fixation may be necessary for more severely displaced fractures 3, 6.
- The goal of treatment is to achieve anatomic reduction and stability of the fracture, while minimizing the risk of complications such as growth arrest or avascular necrosis 3, 6.