Emergency C-spine studies require full set of images

Relying on CT multiplanar reconstructions alone to pick up cervical spine fractures in blunt trauma patients is too risky, according to researchers at the University of Maryland.

An estimated 10,000 cervical spine fractures occur every year in the U.S., and early diagnosis is essential for minimizing damage. Multislice CT has proven far superior to plain film for clearing the cervical spine. It is also faster and more cost-effective for moderate to severe injuries.

Typically, axial images are obtained along with sagittal and coronal multiplanar reconstructions. But some have questioned whether reconstructions alone suffice for diagnostic purposes in blunt trauma patients with suspected cervical spine fractures.

A new retrospective study conducted at the University of Maryland found very high specificity for reconstructed images alone at 98.1%, but sensitivity was just 75.6%.

"Reconstructed images alone cannot be used to detect cervical spine injuries with an acceptable degree of sensitivity," said Dr. Lisa Miller, an assistant professor of diagnostic radiology at Maryland, who presented the results during a session on emergency radiology at the 2006 RSNA meeting.

The study looked at 104 consecutive abnormal blunt trauma cases plus 104 normal control cases seen within a 12-month study period at the Shock Trauma Center. Three reviewers looked independently at the axial images plus reconstructions (15 sagittal and 20 coronal per case) performed on a 16-slice CT scanner. They recorded presence and location of injury if a fracture was detected. One month later, they analyzed the reconstructed images alone. Findings were compared with the radiology reports.

Of 312 fractures, 76 were missed on reconstructed images alone, according to Miller. The most common types of fractures missed were transverse process, isolated fracture of the C-1 arch, and fractures of the lamina.

Unstable fractures were also missed on the sagittal and coronal images, she said.

When all three sets of images (axial, sagittal, and coronal) are used to make a diagnosis, radiologists have three opportunities to pick up fractures. But with reconstructions only, they look at the data just twice. Also, some fractures are more clearly seen on axial images.

"Undoubtedly, as software improves, our ability to make the diagnosis on 2D or even 3D images will improve. We are just not there yet," Miller said.