Researchers consider use of MRI after negative CT scan
Relying solely on a negative or normal multidetector computed tomography (MDCT) to ensure that a trauma patient doesn’t have issues with the cervical spine can lead to missed injuries, according to Mitchel B. Harris, MD, FACS, at the 2009 annual meeting of the Orthopaedic Trauma Association.
“Both CT alone and CT with magnetic resonance imaging (MRI) are useful,” he said. “CT shows the bony pathology more clearly and MRI is more sensitive at uncovering soft-tissue pathology.”
A controversy continues, however, about whether a negative CT scan is sufficient to rule out injuries to the cervical spine of the trauma patient who cannot be adequately examined or whether it should be followed by an MRI.
“The evaluation of the cervical spine in patients who have sustained blunt trauma remains difficult,” Dr. Harris stated.
“Controversy exists about the degree to which an isolated negative CT scan obviates the need for continued immobilization in a cervical collar,” he continued. “Some studies have proposed that an isolated negative CT scan of the cervical spine is sufficient to ‘clear the cervical spine.’
“We wanted to know whether adding a MRI provided useful information that altered treatment after a negative CT scan,” Dr. Harris explained.
Computer search yields large study group
The researchers conducted a meta-analysis of studies published from January 2000 to December 2008. They used combinations of several search terms—“cervical,” “computed tomography,” “spinal injuries,” and “magnetic resonance imaging”—to identify the studies.
“Included in this meta-analysis were any prospective and retrospective studies in which patients had a negative or normal MDCT scan and a MRI for the purposes of cervical spine clearance,” Dr. Harris explained.
Additional inclusion criteria were as follows:
- Reports on clinical decisions (such as cervical collar removal, surgical intervention, or prolonged use of collar) made based on positive MRI findings
- Information on how accuracy of findings was determined
The initial search identified 58 studies, 11 of which met the inclusion criteria. The 11 studies covered a total of 1,550 blunt trauma patients who had a negative MDCT scan and an MRI.
All of the studies had more than 30 patients, and several had more than 100 patients. Based on the evidence-based criteria as defined by The Journal of Bone and Joint Surgery, the studies were graded at least a Level III.
Of the 11 studies, 6 were retrospective. Researchers found no prospective, randomized, controlled trials comparing MRI and CT to CT alone.
MRIs yield mixed results
The results of using MRIs in these studies varied. In one study, 1 percent of the patients were found to need surgical stabilization based on the MRI. In another study, however, MRI use identified abnormal findings in 5.5 percent of patients, but these findings were clinically insignificant.
Overall, the MRI studies did identify a clinically significant injury that required a change in management in 6 percent of the patients (n=96).
Other studies have found MRI comparable to or better than CT imaging in detecting certain conditions. “In light of its ability to detect ligamentous, soft-tissue, and osseous edema, many clinicians contend that the sensitivity of MRI for detecting injuries exceeds that of CT,” Dr. Harris explained.
How to clear the cervical spine
Dr. Harris and his colleagues believe the optimal method for cervical spine clearance is based on the “2 out of 3 rule.” The concept, introduced by the investigators, suggests that 2 out of the following 3 elements are needed to clear a cervical spine patient—a good clinical exam, a negative MDCT scan, and a negative MRI.
“Either the clinician needs a negative CT scan and a negative MRI or a good clinical exam and a negative CT scan or a good clinical exam and a negative MRI,” Dr. Harris concluded.
The authors report the following disclosures: Dr. Harris—AO; DePuy, A Johnson & Johnson Company; Medtronic Sofamor Danek; Synthes; OMeGA; Kevin J. McGuire, MD— Globus Medical, EBI; Christopher M. Bono, MD— Journal of Spinal Disorders and Techniques, The Spine Journal, Journal of the AAOS, Life Spine, Synthes Spine; Andrew J. Schoenfeld, MD— no conflicts. No disclosures were available for Natalie Warholic, MA.
Annie Hayashi is the senior science writer for AAOS Now. She can be reached at email@example.com