From the Guidelines
X-rays are the preferred initial imaging modality over MRI for diagnosing suspected Salter-Harris fractures of the distal fibular physis in a 14-year-old male with a right lateral ankle injury, due to their high sensitivity and cost-effectiveness. The American College of Radiology recommends radiographs as the initial imaging study for patients with acute trauma to the ankle, including those with suspected Salter-Harris fractures 1. For a 14-year-old male with a lateral ankle injury and concern for a Salter-Harris type I fracture of the distal fibular physis, spaced X-rays (including stress views) can effectively detect displacement that might not be visible on standard views. While growth plates are indeed radiolucent on X-rays, displacement or widening of the physis can be visualized with proper technique.
The following points support the use of X-rays as the initial imaging modality:
- High sensitivity for detecting ankle fractures, with studies demonstrating between 92% and 99% sensitivity 1
- Cost-effectiveness and accessibility compared to MRI
- Ability to detect displacement or widening of the physis with proper technique
- Recommendation by the American College of Radiology as the initial imaging study for patients with acute trauma to the ankle 1
MRI would provide superior soft tissue detail and could detect bone bruising or occult fractures, but it's usually reserved for cases where X-rays are inconclusive and clinical suspicion remains high, or when ligamentous injury requires further evaluation 1. The standard approach involves initial X-rays followed by MRI only if necessary, balancing diagnostic accuracy with practical considerations like cost, availability, and the potential need for sedation in younger patients. For this specific case, spaced or stress X-rays represent a reasonable first diagnostic step, with MRI as a second-line option if clinical concerns persist despite normal radiographs.
From the Research
Diagnosis of Salter-Harris Fractures
- Salter-Harris fractures are defined as a disruption in the cartilaginous physis of bone with or without the involvement of epiphysis or metaphysis 2.
- These fractures represent around 15-18% of all pediatric fractures and it is essential to diagnose physeal injury as early as possible to prevent long-term complications 2.
Comparison of Imaging Techniques
- Plain radiographs can be deceptive and may underestimate the displacement of Salter-Harris III fractures, whereas MRI or CT scans can provide a more accurate assessment of the fracture displacement 3.
- However, in the case of suspected Salter-Harris I fracture of the distal fibula, MRI evidence suggests that sprains may be more common than previously thought, and the clinical diagnosis of Salter-Harris I fracture may be incorrect in a significant number of cases 4.
Recommendations for Diagnosing Salter-Harris Fractures
- For suspected Salter-Harris I fracture of the distal fibula, spaced x-rays are recommended over MRI to diagnose the fracture, as the growth plate is not visible on x-ray and MRI may not be necessary in all cases 4.
- However, if the diagnosis is still uncertain, an MRI or CT scan may be considered to confirm the presence of a fracture and to assess the extent of the injury 3.
- It is essential to note that the treatment of Salter-Harris fractures depends on the type and severity of the fracture, and early diagnosis and treatment are crucial to prevent long-term complications 2, 5, 6.