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Researchers assess the performance of radiographic imaging of spinal injuries

Evaluation and treatment of patients with suspected cervical spine injury (CSI), often due to blunt trauma, usually involves radiologic imaging. Plain x-rays of the spine usually are the first step in screening such injuries, but they may miss from 20 to 40 percent of cervical spine fractures. Therefore, computed tomography (CT) or magnetic resonance imaging (MRI) are often used as well.

Three studies supported by the Agency for Healthcare Research and Quality (HS08239) and led by William R. Mower, M.D., Ph.D., of the University of California, Los Angeles School of Medicine, recently examined the use of imaging to diagnose CSI. The first study concluded that MRI is not as reliable as CT for excluding CSIs but is better than CT for identifying soft tissue injuries. The second study found that spinal cord injuries among blunt trauma victims that are not revealed on plain back x-rays are rare and occur predominantly among adults. The third study revealed that geriatric victims of blunt trauma are more likely to suffer CSI than younger victims, and that five clinical criteria can save some of them from unnecessary spinal imaging. All three studies are described here.

Holmes, J.F., Mirvis, S.E., Panacek, E.A., and others (2002, September). "Variability in computed tomography and magnetic resonance imaging in patients with cervical spine injuries." Journal of Trauma 53, pp. 524-530.

Although CT has been the radiographic study of choice after obtaining plain x-rays in CSI patients, some centers have begun using MRI more frequently. However, MRI is not reliable for excluding cervical spine injuries, and fractures in particular, according to this multicenter study. The researchers examined the overall clinical performance of CT and MRI (following simple x-ray of the cervical spine) of CSI patients seen at university- and community-based facilities, trauma and nontrauma centers, and in teaching and nonteaching environments. Overall, 688 patients with 1,302 separate CSIs were enrolled. Following plain cervical spine x-rays, two-thirds of these patients underwent CT and one-fifth had MRI, with few patients having both.

CT better identified bony injuries, but MRI better identified spinal cord and soft tissue injuries. For example, MRI and CT respectively identified the following injuries among 124 MRI and 419 CT patients: osseous fractures (55 vs. 97 percent); spinal cord injury (100 vs. 0 percent); vertebral subluxation/dislocation (86 vs. 86 percent); ligamentous injury (100 vs. 25 percent); and unilateral/bilateral locked facets (78 vs. 97 percent). MRI missed 45 percent of identified osseous fractures, which are clinically unstable, indicating a significant limitation of this imaging technique.

In contrast, all 69 patients identified with spinal cord injury had this injury identified by MRI. This is important in managing patients with CSI, and for this reason, MRI is now considered useful in evaluating select patients with neurologic deficits. Neither MRI or CT can be relied on as the sole test to identify vertebral body subluxation because each technique missed at least 18 percent of these injuries. The researchers suggest that CT be used in patients with cervical spine fractures to identify fractures not seen on plain x-rays and for patients whose plain x-rays are inconclusive or suggestive of bony fracture. The role of MRI is less clear, but it likely is best used in evaluating patients with neurologic deficits.

Hendley, G.W., Wolfson, A.B., Mower, W.R., and others (2002, July). "Spinal cord injury without radiographic abnormality: Results of the National Emergency X-Radiography Utilization Study in blunt cervical trauma." Journal of Trauma Injury, Infection, and Critical Care 53, pp. 1-4.

Spinal cord injuries among blunt trauma victims that are not revealed on plain back x-rays are rare and occur predominantly among adults, concludes this study. The researchers analyzed data from the large prospective National Emergency X-Radiography Utilization Study (NEXUS) of blunt cervical spinal trauma to better characterize spinal cord injury without radiographic abnormality (SCIWORA). The database included adults and children with cervical spine trauma who had received plain neck x-rays at the emergency departments at any of 21 U.S. medical centers. Treating physicians decided what type of imaging the patients received. Radiologists at each site interpreted all radiographic studies.

SCIWORA was defined as spinal cord injury demonstrated by MRI, when a complete, technically adequate plain x-ray series, including at least three views, revealed no injury. Of the 34,069 patients in the NEXUS database, 818 (2.4 percent) had CSI, including 27 (0.08 percent) patients with SCIWORA. Over 3,000 children were enrolled, including 30 with cervical spine injury, but none had SCIWORA. The most common MRI findings among SCIWORA patients were central disc herniation (41 percent), spinal stenosis (41 percent), and spinal cord edema or contusion (93 percent). Central cord syndrome was described in 10 cases.

The researchers conclude that SCIWORA is an uncommon injury pattern in general, occurring in only 0.08 percent of all patients enrolled. Pediatric cases of SCIWORA were conspicuously absent in this large series. The central cord syndrome was prospectively identified in one-third of SCIWORA patients. The NEXUS criteria for patients at low risk of CSI (had none of the following: altered level of alertness, intoxication, posterior midline cervical spine tenderness, distracting painful injury, or focal neurologic deficit) were highly sensitive in identifying that these high-risk patients required imaging.

Touger, M., Gennis, P., Nathanson, N., and others (2002, September). "Validity of a decision rule to reduce cervical spine radiography in elderly patients with blunt trauma." Annals of Emergency Medicine 40(3), pp. 287-293.

Elderly patients who suffer from blunt cervical trauma are more likely than younger patients to have cervical spine injury (CSI), perhaps due to osteopenia (reduced bone mass), physical disability, or other age-related conditions. Also, they are more likely to suffer CSI from minor falls. However, use of certain clinical criteria can help avoid unnecessary cervical spine imaging in this group, according to this study. The investigators analyzed the use of five clinical criteria (NEXUS decision instrument) to identify risk of CSI among 2,943 elderly blunt trauma victims (8.6 percent of the entire NEXUS sample of blunt trauma patients treated at 21 U.S. medical centers).

NEXUS defined as "low-risk" patients exhibiting none of the following five criteria: altered level of alertness, intoxication, posterior midline cervical spine tenderness, distracting painful injury, and focal neurologic deficit. The rate of CSI was twice as great among geriatric as nongeriatric patients (4.6 vs. 2.2 percent). Odontoid fractures (in the upper spine) were particularly common in geriatric patients, accounting for 20 percent of geriatric fractures compared with 5 percent of nongeriatric fractures.

NEXUS criteria classified 14 percent of geriatric patients and 12.5 percent of non-geriatric patients as low risk for CSI. CSI occurred in only two low-risk geriatric patients, and these patients' injuries met the definition of a clinically insignificant injury. Therefore, the sensitivity of the NEXUS decision instrument for clinically significant injury in the geriatric group was 100 percent. These findings suggest that use of the NEXUS criteria can substantially reduce unnecessary imaging among geriatric victims of blunt trauma.

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