From the Guidelines
The best way to diagnose a suspected Salter-Harris type 1 fracture of the distal fibula physis in a 14-year-old male with a right lateral ankle injury is to obtain an MRI, as it is the reference standard for ligamentous injury and assessment of stability, and can help exclude Salter 1 fractures in the pediatric population. When the growth plate is not visible on X-ray, and there is tenderness to palpation at the lateral malleoli, anterior talofibular ligament (ATFL), and calcaneofibular ligament (CFL), an MRI would provide a detailed assessment of both the growth plate and surrounding soft tissues 1. The following are key points to consider:
- MRI is the gold standard for evaluating growth plate injuries as it can directly visualize the cartilaginous physis and detect bone marrow edema that indicates injury.
- While CT scanning offers better bone detail, it exposes the patient to radiation and doesn't visualize cartilage well.
- Ultrasound is another option that avoids radiation but is highly operator-dependent and less sensitive than MRI.
- Until definitive imaging, the patient should be treated with protective weight-bearing (crutches or walking boot), rest, ice, compression, and elevation.
- Growth plate injuries require careful management as they can lead to growth disturbances if not properly diagnosed and treated, particularly important in this adolescent patient who likely still has open growth plates.
- Radiography is indicated as the initial imaging study, but it may not detect all fractures, especially in the presence of ligamentous injury or growth plate damage 1. Key considerations for imaging include:
- The Ottawa Ankle Rules (OAR) should be used to determine the need for radiography.
- Weight-bearing radiographs, if possible, provide important information, particularly with fractures of uncertain stability.
- Special scenarios, such as suspected calcaneal fractures or snowboarder’s fracture, may require additional views.
From the Research
Diagnosis of Suspected Salter-Harris Type 1 Fracture
To diagnose a suspected Salter-Harris type 1 fracture of the distal fibula physis in a 14-year-old male with a right lateral ankle injury, the following steps can be considered:
- The growth plate is not visible on X-ray, which is a common challenge in diagnosing Salter-Harris type 1 fractures 2.
- Tenderness to palpation (TTP) at the lateral malleoli, anterior talofibular ligament (ATFL), and calcaneofibular ligament (CFL) is present, which can indicate a potential fracture or ligamentous injury.
Role of Magnetic Resonance Imaging (MRI)
MRI can be a useful diagnostic tool in this scenario:
- A study published in 2010 found that none of the 18 patients with clinically suspected Salter-Harris type 1 fractures of the distal fibula had evidence of fibular growth plate injury on MRI 3.
- Another study published in 2016 found that only 4 out of 135 children (3.0%) with clinically suspected Salter-Harris type 1 fractures of the distal fibula had MRI-confirmed fractures 4.
- A prospective MRI study published in 2016 found that none of the 31 patients with clinically suspected Salter-Harris type 1 fractures of the distal fibula had evidence of fracture on MRI 5.
Alternative Diagnoses
The presence of tenderness to palpation at the lateral malleoli, ATFL, and CFL, and the lack of visibility of the growth plate on X-ray, may suggest alternative diagnoses:
- Ligamentous sprains or injuries, which are common in children with acute ankle injuries 3, 4, 5.
- Bony contusions or bone bruises, which can occur in the absence of a fracture 3, 4.
- Occult fractures, which may not be visible on initial X-rays but can be detected on follow-up radiographs or MRI 6.
Diagnostic Approach
Based on the available evidence, a diagnostic approach that includes:
- Clinical evaluation and physical examination to assess for tenderness to palpation and ligamentous instability.
- Initial X-rays to rule out obvious fractures or dislocations.
- Consideration of MRI or follow-up radiographs to detect occult fractures or ligamentous injuries.
- A high index of suspicion for ligamentous sprains or injuries, given the high false-positive rate of clinically suspected Salter-Harris type 1 fractures of the distal fibula 3, 4, 5.