From the Guidelines
For a 14-year-old male with a suspected Salter-Harris type 1 fracture of the distal fibular physis, an MRI is the best diagnostic approach, as it provides superior visualization of both bone and soft tissue structures, and can detect bone marrow edema at the physis that would indicate a Salter-Harris injury even when X-rays appear normal. This approach is supported by the American College of Radiology, which recommends MRI as the reference standard for ligamentous injury and assessment of stability, particularly in athletes 1. The initial X-ray may not show the growth plate, and spaced X-rays may not be sensitive enough to detect non-displaced Salter-Harris I fractures, which are often radiographically occult.
Key benefits of using MRI in this scenario include:
- Detection of bone marrow edema at the physis, indicating a Salter-Harris injury
- Evaluation of ligamentous structures, allowing for comprehensive assessment of both the suspected growth plate injury and potential associated ankle ligament damage
- Guidance of appropriate treatment decisions for the adolescent patient
- Particular importance in adolescents, where growth plate injuries require accurate diagnosis to prevent growth disturbances, as highlighted in the context of acute trauma to the ankle 1.
In contrast to spaced X-rays, MRI provides a more detailed and accurate assessment of the injury, which is critical for treatment planning and return to sport assessment, especially in athletes 1. Therefore, an MRI is the most appropriate diagnostic approach for this patient.
From the Research
Diagnostic Approaches for Suspected Salter-Harris Type 1 Fracture
- The use of Magnetic Resonance Imaging (MRI) is supported by studies 2, 3 as it allows for the detection of occult fractures, alteration of Salter Harris staging, and change in patient management.
- A study by 3 found that the clinical diagnosis of Salter-Harris type 1 fracture of the distal fibula was incorrect in 100% of cases, with MRI identifying ligamentous sprains and/or bony contusions in almost 90% of patients.
- The use of spaced X-rays is not explicitly supported by the provided studies, but it is mentioned in 3 that repeat ankle X-rays at 4 weeks were taken, and only one patient's radiographs demonstrated a healing fracture.
Comparison of Imaging Modalities
- MRI is shown to be more effective than plain radiographs in evaluating growth plate injuries 2 and detecting occult fractures 3.
- A study by 4 found that plain x-rays significantly underestimated the displacement of Salter-Harris type III fractures of the distal femur compared to MRI or CT scans.
- The use of MRI is also supported by a systematic review 5 which found that the most common injuries of the pediatric ankle are ATFL sprain and osteochondral avulsions, rather than Salter-Harris type 1 fractures.
Clinical Implications
- The results of the studies suggest that MRI should be considered as a diagnostic tool for suspected Salter-Harris type 1 fractures of the distal fibula, especially when the growth plate is not visible on initial X-ray.
- The high incidence of ligamentous sprains and bony contusions in patients with suspected Salter-Harris type 1 fractures should be taken into consideration when ordering radiological examinations and deciding on treatment modalities 3, 5.