From the Guidelines
A weight-bearing x-ray is necessary for the diagnosis of a Lisfranc fracture, as it significantly improves diagnostic accuracy by revealing subtle injuries that may not be apparent on non-weightbearing radiographs. This is because non-weightbearing radiographs are not reliable for detection of subtle injuries, and weightbearing views have been shown to increase the abnormal alignment at the Lisfranc joint, making it easier to identify a Lisfranc injury 1. The inclusion of both feet on AP radiographs can also help in the detection of subtle malalignment when compared with the uninjured side.
When evaluating a patient with suspected Lisfranc injury, it is essential to consider the clinical signs and symptoms, as well as the radiographic findings. Weightbearing radiographs can help identify subtle displacements that become apparent only when the foot is under load, such as widening between the first and second metatarsals.
Key findings on weight-bearing X-rays include:
- Widening of more than 2mm between the first and second metatarsal bases
- Any displacement at the tarsometatarsal joints If clinical suspicion remains high despite negative X-rays, advanced imaging such as CT or MRI should be considered, with CT being particularly useful for surgical planning and MRI better for detecting ligamentous injuries 1. Early and accurate diagnosis is crucial, as missed Lisfranc injuries can lead to chronic pain, post-traumatic arthritis, and significant disability if not properly treated.
From the Research
Diagnostic Approaches for Lisfranc Fractures
- Weight-bearing x-rays are considered a useful diagnostic tool for Lisfranc fractures, as they can help identify subtle injuries that may not be apparent on non-weight-bearing radiographs 2.
- A study found that weight-bearing radiographs were positive in 54% of cases, and subsequent CT scans were reported as either equivocal or negative in these cases, suggesting that weight-bearing x-rays can be a reliable first-line investigation 2.
- Another study noted that conventional non-weight-bearing radiographs can overlook up to 30% of unstable Lisfranc injuries, highlighting the importance of weight-bearing x-rays in diagnosis 3.
Comparison with Other Imaging Modalities
- CT scans can provide detailed information about fracture patterns and comminution, but may not be necessary for initial diagnosis and management of suspected subtle Lisfranc injuries 2, 3.
- MRI can predict instability and is useful for diagnosing Lisfranc ligament injuries, but may not be readily available in the acute setting 3, 4, 5.
- A study comparing the diagnostic performance of X-ray, CT, and MRI found that non-weight-bearing X-rays had poor diagnostic accuracy for subtle Lisfranc injuries, while CT and MRI had higher sensitivity and specificity 5.
Clinical Implications
- Weight-bearing x-rays can help identify patients who require surgical treatment, as a positive weight-bearing radiograph was found to be correlated with surgical treatment 2.
- The distance between the base of the first and second metatarsals can be measured on X-ray, and a distance greater than 2 mm may indicate a Lisfranc injury 4.
- Clinical and radiological signs of a Lisfranc injury should be carefully evaluated, and weight-bearing radiographs or CT scans may be necessary to confirm the diagnosis 6.