From the Guidelines
X-ray is the best initial imaging modality to rule out a non-displaced fracture of the distal fibula. A standard ankle series should include anteroposterior (AP), lateral, and mortise views, as recommended by the American College of Radiology 1. This approach is supported by studies demonstrating between 92% and 99% sensitivity for detecting ankle fracture using the Ottawa Ankle Rules (OAR) criteria, with less than 2% of those who are negative for fracture using the OAR actually having a fracture 1.
The use of weight-bearing radiographs, if possible, provides important information, particularly with fractures of uncertain stability, because the most important criterion in treatment of malleolar fractures is stability 1. Special attention to the lateral process fracture of the talus, also known as snowboarder’s fracture, is recommended in patients with swelling inferior to the lateral malleolus in the appropriate clinical setting to exclude an erroneous diagnosis of a lateral ankle sprain 1.
Some key points to consider when using X-ray for this purpose include:
- The OAR criteria are validated in children >5 years of age and should not be used in patients meeting the exclusionary criteria listed above 1
- Typical radiographic protocols should include three standard views: anteroposterior, lateral, and mortise views to include the base of the fifth metatarsal bone distal to the tuberosity 1
- Ultrasound (US) may be useful but is not typically considered the first line of imaging for the evaluation of acute trauma to the ankle with positive OAR 1
If clinical suspicion remains high despite negative X-rays, an MRI would be the next best option as it has superior sensitivity for detecting occult fractures. CT scanning may also be considered as an alternative when MRI is unavailable or contraindicated. X-ray is recommended first because it is readily available, cost-effective, and has good sensitivity for most fractures, as noted in the study by Smith et al 1.
From the Research
Imaging Modalities for Non-Displaced Fracture of Distal Fibula
- The best imaging modality to rule out a non-displaced fracture of the distal fibula is not explicitly stated in the provided studies.
- However, the studies suggest that radiographic exams, including stress X-rays and weight-bearing radiographs, can be useful in detecting associated mortise instability and assessing ankle stability 2, 3.
- CT scans can also be used to evaluate the rotational deformity of the fibular fragment and assess the relationship between the tibia and fibula 4.
- In some cases, additional diagnostics such as MRI scans or gravity stress tests may be necessary to differentiate between stable and unstable fractures 5.
- CT scans are also recommended for preoperative examination of Maisonneuve fractures to assess the variable injury pattern and position of the fibula in the fibular notch 6.
Key Findings
- Radiographic exams, including stress X-rays and weight-bearing radiographs, are commonly used to assess ankle stability and detect associated mortise instability.
- CT scans can provide valuable information on the rotational deformity of the fibular fragment and the relationship between the tibia and fibula.
- Additional diagnostics such as MRI scans or gravity stress tests may be necessary in some cases to determine the stability of the fracture.
- The choice of imaging modality may depend on the specific clinical presentation and the suspected type of fracture. 2, 3, 4, 5, 6