From the Guidelines
For a 14-year-old male with a suspected Salter-Harris type 1 fracture of the distal fibular physis, MRI is the best diagnostic imaging modality to evaluate for a fracture and potential displacement, especially when the growth plate is not visible on initial x-ray. This recommendation is based on the high sensitivity of MRI in detecting physeal injuries and its ability to directly visualize the cartilaginous growth plate, as noted in the American College of Radiology's appropriateness criteria for acute trauma to the ankle 1. The use of MRI is particularly important in this case, as it can help exclude Salter 1 fractures in the pediatric population, which can be difficult to diagnose with conventional radiography alone 1.
Some key points to consider when evaluating this patient include:
- The growth plate being "invisible" on initial X-ray is typical for Salter-Harris I injuries, making them notoriously difficult to diagnose with conventional radiography alone.
- MRI can directly visualize the cartilaginous growth plate and detect subtle fractures that may not be visible on plain radiographs.
- Spaced or stress X-rays might show displacement or widening of the physis, but they lack sensitivity for non-displaced Salter-Harris injuries, particularly type I fractures.
- MRI can also assess associated soft tissue injuries to the ankle ligaments that may be involved in this case, which is critical for treatment planning and return to sport assessment, as noted in the study by Grossterlinden et al, as referenced in 1.
Overall, the use of MRI in this case would provide more definitive information about both the presence of a fracture and any displacement, allowing for appropriate treatment planning for this adolescent patient with open growth plates.
From the Research
Diagnostic Imaging Modalities
To evaluate a suspected Salter-Harris type 1 fracture of the distal fibular physis in a 14-year-old male, where the growth plate is not visible on initial x-ray, the best diagnostic imaging modality can be determined by considering the following factors:
- The ability to visualize the growth plate and detect potential displacement
- The sensitivity and specificity of the modality in detecting fractures and other injuries
Comparison of Spaced X-rays and Magnetic Resonance Imaging (MRI)
- Spaced x-rays may not be sufficient to detect occult fractures or growth plate injuries, as they may not show visible fractures or displacement on initial radiographs 2, 3
- MRI is a more sensitive modality for detecting growth plate fractures, ligamentous sprains, and bony contusions, and can help confirm the diagnosis of a Salter-Harris type 1 fracture 4, 3
- Studies have shown that MRI can detect occult fractures and growth plate injuries that are not visible on x-ray, and can help differentiate between fractures and sprains 4, 3
Key Findings
- A study published in 2010 found that none of the 18 patients with suspected Salter-Harris type 1 fractures of the distal fibula had evidence of fibular growth plate injury on MRI, and instead had ligamentous sprains, bony contusions, or other injuries 4
- A study published in 2016 found that only 3.0% of children with radiograph-negative lateral ankle injuries had MRI-confirmed Salter-Harris type 1 fractures of the distal fibula, and that most children had ligament injuries or sprains 3
- Another study published in 2008 found that 18% of children with acute ankle injuries and normal radiographs had evidence of periosteal new bone formation on follow-up radiographs, suggesting the presence of an occult fracture 2
Considerations for Diagnostic Imaging
- The choice of diagnostic imaging modality should be based on the clinical presentation and suspected diagnosis
- MRI may be a more appropriate modality for detecting growth plate fractures and other injuries in children with suspected Salter-Harris type 1 fractures of the distal fibula, especially when the growth plate is not visible on initial x-ray 4, 3