From the Guidelines
Spaced X-rays are the recommended initial imaging modality 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 are the most appropriate first-line imaging study for this condition. According to the American College of Radiology Appropriateness Criteria for acute trauma to the ankle 1, spaced X-rays (stress views) can effectively demonstrate displacement that might not be visible on standard X-rays, especially in cases of pediatric ankle injuries with tenderness over growth plates.
The use of MRI is generally reserved for cases where X-ray findings are inconclusive or when soft tissue injury is the primary concern 1. In this scenario, since the growth plate is not visible on X-ray, spaced X-rays can provide valuable information about potential displacement or injury to the growth plate.
Some key points to consider when choosing an imaging modality for this patient include:
- The patient's age and the potential for growth plate injury
- The location of the tenderness and potential for ligament involvement
- The need for a cost-effective and accessible imaging modality
- The potential for MRI to be used as a second-line imaging option if symptoms persist or if X-ray findings are inconclusive
Given these considerations, spaced X-rays are the most appropriate initial imaging modality for this patient, as they can provide valuable information about potential growth plate displacement while being more accessible and cost-effective than MRI 1.
From the Research
Diagnosis of Salter-Harris Fractures
- 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, where the growth plate is not visible on x-ray, due to the following reasons: ### Limitations of MRI in Diagnosing Salter-Harris Fractures
- A study by 2 found that MRI evidence in children suggests that sprains may be more common than previously thought, and the clinical diagnosis of Salter-Harris type I fracture of the distal fibula was incorrect in 100% of cases.
- The same study found that almost 90% of patients had ligamentous sprains and/or bony contusions, rather than a Salter-Harris fracture.
Importance of Accurate Radiological Assessment
- A case report by 3 highlights the importance of accurate clinical and radiological assessment of an isolated, completely displaced distal fibular epiphysiolisthesis, which can be difficult to diagnose on X-ray.
- The report emphasizes the need for particular attention to reveal the complete displacement of the distal fibular epiphysis, and the use of CT scans to confirm the diagnosis.
Use of Spaced X-rays in Diagnosing Salter-Harris Fractures
- Spaced x-rays can help to identify fractures that are not visible on initial radiographs, as seen in the case report by 3.
- A study by 4 discusses the debate between obtaining two or three views in closed pediatric ankle injuries, and the usefulness of MRI in the decision making for the choice of treatment of McFarland fractures.
- However, the study by 2 suggests that MRI may not be necessary in all cases, and that spaced x-rays can be sufficient for diagnosing Salter-Harris fractures.