Comparative Evaluation of MRI and CT in the Diagnosis of Ankle Fractures: A Prospective Diagnostic Accuracy Study

When a person twists an ankle, the pain is immediate and sharp, but the true extent of the damage often remains hidden beneath the skin. The ankle is a complex machine, built from twenty-eight bones, thirty-three joints, and over one hundred ligaments that work together to keep the body upright and moving. When this structure breaks, doctors must decide quickly whether a bone has cracked or if the soft tissues holding the joint together have torn. For decades, the standard approach has been to look at the bones using X-rays, and if those are unclear, to use a computed tomography scan, or CT. A CT scan uses X-rays to create a detailed, three-dimensional map of the bone, showing cracks and breaks with great clarity. However, this method has a blind spot: it is excellent at seeing hard bone but poor at seeing soft tissue like ligaments, tendons, and cartilage. This is a significant problem because a torn ligament can destabilize the joint just as much as a broken bone, yet it often goes unnoticed on a CT scan. Furthermore, the radiation used in CT scans poses a risk to certain groups, such as pregnant women and children, making doctors eager to find a safer way to see the full picture of an injury.

To solve this puzzle, a team of researchers at Peking University Third Hospital and collaborating institutions conducted a direct comparison between the traditional CT scan and magnetic resonance imaging, known as MRI. Unlike the CT scan, an MRI uses powerful magnets and radio waves to create images, a process that involves no radiation at all. While MRI is famous for its ability to show soft tissues in vivid detail, its ability to see bone fractures has sometimes been questioned. The researchers wanted to know if MRI could match the CT scan in spotting broken bones while also being the superior tool for spotting torn ligaments. They enrolled ninety-four patients who had suffered ankle injuries and suspected fractures. Every single patient underwent both a CT scan and an MRI. To ensure the results were accurate, the team did not rely on just one opinion. Instead, they created a "gold standard" diagnosis by combining the clinical exam, what the surgeons saw during surgery, and the consensus of experienced orthopedic doctors and radiologists. This final diagnosis served as the truth against which the two imaging tests were measured.

The study revealed a clear division in the strengths of these two technologies. When it came to identifying broken bones, both the CT scan and the MRI performed exceptionally well, especially when read by experienced senior surgeons. The senior doctors were able to spot every single fracture using the CT scan, and they missed only a tiny fraction using the MRI. This suggests that for the specific task of finding a crack in the bone, the MRI is just as reliable as the CT scan, offering a safe, radiation-free alternative that does not sacrifice accuracy. However, the story changed dramatically when the researchers looked at ligament injuries. The CT scan struggled significantly here, often failing to see torn ligaments entirely. In fact, when junior surgeons reviewed the CT scans, they identified ligament tears in only a handful of cases, missing the vast majority of them. Even senior surgeons, who are highly experienced, missed most ligament injuries on the CT scans.

In stark contrast, the MRI excelled at revealing soft tissue damage. Both junior and senior surgeons were able to identify ligament tears with near-perfect accuracy when using the MRI. The data showed that the MRI was significantly better than the CT scan at finding these hidden soft tissue injuries, regardless of how much experience the doctor reading the scan had. This finding is crucial because missing a ligament tear can lead to long-term instability and arthritis in the ankle. The researchers also looked at how well the doctors could classify the specific type of fracture using a system called Lauge-Hansen, which describes how the injury happened. Both imaging methods allowed for highly consistent classification, though the MRI provided a slightly more complete picture by showing not just the bone break, but also the bruising inside the bone and the condition of the cartilage.

The study concludes that while the CT scan remains a powerful tool for seeing bone fractures, the MRI offers a more comprehensive evaluation of ankle trauma. It matches the CT scan in finding broken bones but surpasses it completely in detecting ligament damage. This makes the MRI particularly valuable for patients who need to avoid radiation, such as pregnant women and children, and for cases where the injury involves complex soft tissue damage. The researchers noted, however, that reading an MRI requires skill and experience; the doctors who interpreted the scans needed training to get the best results. Ultimately, this work suggests that for a full understanding of an ankle injury, the MRI provides a clearer, safer, and more detailed view of the damage than the traditional CT scan, helping doctors make better decisions about how to treat the patient.