From the Guidelines
CT scans are not routinely needed for diagnosing femoroacetabular impingement (FAI), and MRI is the preferred imaging modality after plain radiographs. The primary imaging modality for FAI is typically plain X-rays, which can show bone abnormalities like cam deformities (abnormal femoral head-neck junction) or pincer deformities (acetabular overcoverage) 1.
Key Points to Consider
- MRI, particularly MR arthrography, is often the next step as it provides better visualization of labral tears and cartilage damage that commonly accompany FAI 1.
- CT scans are generally reserved for specific situations, such as preoperative planning when detailed 3D bone anatomy is needed, evaluating complex deformities, or when MRI is contraindicated 1.
- The diagnostic approach typically begins with a thorough clinical examination, followed by plain radiographs, and then advanced imaging like MRI if necessary 1.
- CT exposes patients to radiation, which is why it's not the first-line imaging choice 1.
When to Use CT Scans
- CT would be ordered only if your orthopedic surgeon needs additional information about bone structure that other imaging methods cannot provide adequately 1.
- In some cases, CT arthrography may be used to evaluate chondral lesions, but MR arthrography is generally superior for evaluating labral tears 1.
From the Research
Imaging Modalities for Femoroacetabular Impingement
- Femoroacetabular impingement (FAI) is a condition where abnormal anatomic relationships within the hip joint lead to articular damage 2.
- Imaging plays a critical role in the assessment of patients with FAI, and various modalities are used to evaluate the condition 3, 4, 5, 6.
Role of CT in Femoroacetabular Impingement
- CT remains a valuable tool for planning complex surgical corrections in patients with FAI 6.
- While CT is not always necessary for the initial diagnosis of FAI, it can be useful in certain cases, such as when advanced imaging is required for surgical planning 6.
Alternative Imaging Modalities
- Pelvic radiography with dedicated hip projections is the basis of the diagnostic workup of patients with suspected FAI 6.
- MRI, including unenhanced MRI or MR arthrography, is used to evaluate chondrolabral lesions and assess the presence of a cam deformity 4, 5, 6.
- Radial imaging and large-FOV fluid-sensitive sequences are also used to accurately determine the presence of a cam deformity and exclude conditions that can mimic or coexist with FAI 6.