Will a non-contrast computed tomography (CT) scan of the wrist rule out a scaphoid fracture?

From the Guidelines

A non-contrast CT scan of the wrist can detect most scaphoid fractures but cannot completely rule them out in all cases. According to the most recent study 1, CT without IV contrast has been shown to be beneficial in operative planning for scaphoid fracture, but it may still miss very small or hairline fractures, particularly those that occur within the first 24-48 hours after injury. The study highlights that CT provides a detailed assessment of the cortical and trabecular bone with a high spatial resolution, making it ideal for assessing fracture healing, malunion, and articular surface incongruity. However, CT has decreased contrast resolution and lower sensitivity in the detection of soft tissue abnormalities compared to MRI and US.

Some key points to consider when using a non-contrast CT scan to rule out a scaphoid fracture include:

• CT is more sensitive than plain X-rays, detecting approximately 85-95% of scaphoid fractures 1
• CT may still miss very small or hairline fractures, particularly those that occur within the first 24-48 hours after injury
• If clinical suspicion for a scaphoid fracture remains high despite a negative CT, additional imaging such as MRI or a follow-up examination in 10-14 days may be necessary
• MRI is considered the gold standard for detecting occult scaphoid fractures with nearly 100% sensitivity 1

In terms of management, immobilization in a thumb spica splint is often recommended until fracture is definitively ruled out, even with negative initial imaging. This approach prioritizes the patient's quality of life and reduces the risk of further injury or complications. Overall, while a non-contrast CT scan can be a useful tool in detecting scaphoid fractures, it should be used in conjunction with clinical judgment and other imaging modalities to ensure accurate diagnosis and effective management.

From the Research

Diagnostic Accuracy of Non-Contrast CT for Scaphoid Fractures

• The sensitivity and specificity of CT scans for diagnosing scaphoid fractures were found to be 81.5% and 96.0%, respectively, in a systematic review and meta-analysis 2.
• A study comparing CT and MRI for diagnosis of suspected scaphoid fractures found that CT had a sensitivity of 67%, specificity of 96%, and accuracy of 91% 3.
• Another study found that CT reformations along the long axis of the scaphoid had a sensitivity of 67%, specificity of 96%, and accuracy of 91%, which were better than CT reformations in the plane of the wrist, but the differences were not significant 4.

Comparison with Other Imaging Modalities

• MRI was found to have higher sensitivity and specificity than CT scan, bone scintigraphy, or ultrasound for diagnosing scaphoid fractures, with sensitivity and specificity of 94.2% and 97.7%, respectively 2.
• A study found that MRI had a sensitivity of 67%, specificity of 89%, and accuracy of 85% for diagnosing scaphoid fractures, which were comparable to CT 3.

Limitations of Non-Contrast CT

• Non-contrast CT may not be able to detect all scaphoid fractures, especially those that are radiographically occult 5, 6.
• The diagnostic performance characteristics of CT scans may be affected by the plane of reformation, with reformations along the long axis of the scaphoid potentially being more accurate than those in the plane of the wrist 4.