From the Guidelines
For a 14-year-old male with suspected Salter-Harris type I fracture of the distal fibular physis, where the growth plate is not visible on initial x-ray, an MRI is the best diagnostic approach to evaluate the potential fracture and displacement. This recommendation is based on the need for superior soft tissue and cartilage visualization that can detect physeal injuries not apparent on plain radiographs, as indicated by the American College of Radiology guidelines for acute trauma to the ankle 1. The initial use of radiography, including anteroposterior, lateral, and mortise views, is appropriate for detecting ankle fractures, with a sensitivity of 92% to 99% 1. However, in cases where the growth plate is not visible, and there is a high clinical suspicion of a fracture, MRI is preferred due to its ability to identify bone marrow edema, growth plate disruption, and associated ligamentous injuries that may be present 1. While weight-bearing radiographs can provide important information on fracture stability, they are less sensitive than MRI for detecting non-displaced Salter-Harris injuries, particularly type I fractures 1. Some key points to consider in the diagnostic approach include:
- The Ottawa Ankle Rules (OAR) are validated in children >5 years of age and should be used to determine the need for initial radiographs 1.
- Special views, such as the axial Harris-Beath view or Broden view, may be necessary in certain scenarios, such as suspected calcaneal fractures or lateral process fractures of the talus 1.
- Ultrasound may be useful in some cases, but it is not typically considered the first line of imaging for acute trauma to the ankle 1. The MRI findings will guide appropriate treatment decisions, which is especially important in adolescents with open growth plates to prevent growth disturbances or ankle instability. Treatment recommendations would depend on the MRI findings but typically involve immobilization for 3-4 weeks for non-displaced fractures.
From the Research
Diagnostic Approaches for Suspected Salter-Harris Type 1 Fracture
- The growth plate is not visible on initial x-ray, making it challenging to diagnose a Salter-Harris type 1 fracture of the distal fibular physis 2.
- Stress views may be necessary to show an undisplaced fracture, as the overlapping of the physis and metaphysis can minimize specific physeal separation and displacement 2.
- A CT scan can confirm the diagnosis of an isolated, completely displaced distal fibular epiphysiolisthesis, which may be difficult to diagnose on X-ray 3.
Comparison of Spaced X-rays and Magnetic Resonance Imaging (MRI)
- There is no direct comparison of spaced x-rays and MRI in the provided studies for the diagnosis of a Salter-Harris type 1 fracture of the distal fibular physis.
- However, MRI is not mentioned as a diagnostic tool in the provided studies, while x-rays and CT scans are used to diagnose and evaluate fractures of the distal fibula 2, 4, 3.
Potential Complications and Considerations
- Premature physeal closure, fibular growth disturbance, syndesmotic instability, and medial (deltoid ligament) injury are potential complications of a displaced Salter-Harris type 1 fracture of the distal fibula 4.
- Growth arrest in the distal fibular physis may result in either proximal or distal sliding of the fibular metaphysis in relation to the tibial metaphysis, leading to valgus deformity of the ankle 5.