Helical CT scans may provide good injury detection without plain films

Results suggest savings in time, money — and radiation.

Issue: February 2006

Helical CT scans — used alone — may prove more accurate in detecting cervical spine injuries than adequate plain films, according to researchers from West Virginia University.

The researchers reviewed adequate plain films of the cervical spine taken from 194 trauma patients and discovered that adequate plain films identified only 12 of the 25 injuries detected with helical CT scans. They also noted in their abstract that adequate plain films had a lower positive predictive value compared to helical CT scans (81% vs. 89%).

“The clinical relevance is that helical CT can be safely used alone to radiographically evaluate the cervical spine in trauma patients,” said Patrick T. McCulloch, MD, an orthopedist with the university. “And therefore, if a helical CT scan is obtained in a trauma patient, additional plain films will not need to be obtained as well,” he said. “This could save you time, money and radiation." The research constitutes one of the first large studies examining the accuracy of helical CT scans when used alone, McCulloch said.

The helical CT scans missed one fracture, lending to a 99.7% negative predictive value. “We think this is the most important [finding], because it shows the ability of an imaging study to adequately identify that a patient has not had an additional injury and therefore does not need further immobilization,” McCulloch said during his presentation at the Orthopaedic Trauma Association 21st Annual Meeting.

The researchers collected plain films and helical CT scans from 407 trauma patients between July 2002 and February 2004. Of these patients, 58 sustained cervical spine injuries. The study included patients older than 18 years with a mean severity score of 12.5. Most patients were men.

Two independent radiologists reviewed the initial readings and performed a second study reading one month after injury. The investigators blinded the radiologists to both readings. “They documented whether the films were adequate and whether there was an acute process,” McCulloch said. Finally, the researchers compared the initial or control readings with the study readings.

Inadequate films

The investigators rated 52% of the plain films as inadequate and found adequate films for 194 patients. “[From] this, we then can conclude that adequate plain films are difficult to obtain in a majority of trauma patients,” he said.

McCulloch and his colleagues noted 98% specificity for both imaging studies, but “there was a significant difference in the sensitivity, positive predictive value, and negative predictive value between helical CT and adequate plain films, with helical CT being better.” Nearly half of 25 patients with cervical spine injuries had adequate plain films read as no acute process. “So, from this we conclude that adequate plain films frequently miss injuries that are found on helical CT.”

The researchers also found that readings from adequate plain films showed a 93% negative predictive value compared to 99.7% for helical CT scans, they wrote. During a study reading of the CT scans, investigators overlooked one fracture, which was noted on plain film. In retrospect, the fracture was evident on the CT scan, McCulloch said. “And so we feel that this was not a shortcoming of helical CT but rather due to human error, which can't be eliminated.”

Study limitations

McCulloch also pointed to limitations in the study. The patients included in the research were not consecutive cases. In addition, the study may have contained selection bias. The researchers found that more patients with injuries received helical CT scans than non-injured cases.

The research also excluded ligamentous injuries. “So this does not take away the need for flexion extension or MRI,” McCulloch said. “And we do concede that there is still a group of low-risk patients in which plain films are probably more appropriate.”

McCulloch received institutional support from the Jon Michael Moore Trauma Center, West Virginia University Grant

For more information:
McCulloch PT, France JC, Jones DL, et al. A prospective comparison of helical CT alone versus plain films with adjunct CT for radiographic evaluation of the cervical spine in trauma patients. #28. Presented at the Orthopaedic Trauma Association 21st Annual Meeting. Oct. 19-22, 2005. Ottawa.