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Copyright 2004 Evaluating the Cervical Spine in the Wilderness Silent cervical spine fractures During a hike in the backcountry, fifteen miles from the trailhead, John slips and falls down a moderately steep slope, sliding on his side and back until banging up against a tree twenty feet down the hill. Apart from some cuts and scrapes, he appears to have no injuries. One of your concerns, of course, is that John may have suffered an injury to his cervical spine. Here is your dilemma. On the one hand, you can immobilize him and pack him out as best you can, effectively ending the hike and causing a great deal of physical and psychological discomfort for everyone involved, especially John; or you can let things be and resume the hike, with the risk that John may in fact have suffered a silent cervical spine fracture that could eventually have devastating consequences. What do you do? Emergency room doctors have to make similar decisions. Any blunt trauma accident may implicate the cervical spine. When should a patient be given a neck x-ray? On the one hand, there is the risk of a silent fracture, with its potential medical and legal consequences; on the other hand, there is the question of unnecessary health care expenditures and needless radiation exposure. Fortunately, two decision rules for this clinical decision have been tested in large-scale multicenter studies, and have in fact been tested against each other. These hospital criteria can give some guidance for making the evacuation decision in the wilderness. Judging a test There are two kinds of mistakes a test can make. A test for a particular condition can yield a false negative – that is, fail to detect the condition in a patient who has it; or it can yield a false positive – that is, find the condition in a patient who does not have it. A test that produces few false negatives is said to be sensitive; one that produces few false positives is said to be specific. It should be clear that sensitivity and specificity are correlative. A test that is sensitive enough to find all instances of a condition is bound to turn up a certain number of false positives as well; a test that is specific enough to catch only that particular condition and none other is bound to miss a certain number of cases on the margins. The ideal test for, say, cervical spine fractures would detect all and only cervical spine fractures in the people tested. No test is ideal. We would, of course, want a decision rule for detecting a cervical fracture to be sensitive, since the results of a false positive can be costly and annoying, but the results of a false negative can be devastating. Specificity, of course, is nice too; we don’t want to be immobilizing people who don’t need it. But it is better to immobilize John and pack him out, only to be told there’s nothing wrong with him, than to continue the hike and have him develop a serious neurological injury. The NEXUS Criteria One set of decisionmaking criteria developed out of the National Emergency X-Radiography Utilization Study (NEXUS). This was a well designed, multicenter study, carried out at 21 centers across the United States, and involving 34,069 patients, of whom 818 had x-ray evidence of cervical spine injuries. The study sought to discover whether just five relatively simple questions, listed below, correctly predicted patients who had a low probability of injury and thus for whom cervical spine radiography would be unnecessary. These NEXUS Low-Risk Criteria (NLC) are the following:
Patients who met all of these criteria were classified as low risk. Out of the 818 patients who actually had cervical-spine injury, only eight were mistakenly classified as low-risk. Out of the 578 patients who actually had clinically significant cervical-spine injury, only two were mistakenly classified as low-risk. That is considered a highly sensitive test (Hoffman, Mower, Wolfson, Todd, Zucker, & National Emergency X-Radiography Utilization Study Group, 2000). Could the test be made any simpler – say, by eliminating one or more of the five criteria? Apparently not. A substudy was to conducted to determine whether each of the five individual criteria is necessary for the decision instrument to maintain its high sensitivity. Twenty-nine percent of patients with cervical-spine injury and 30 percent of patients with significant cervical-spine injury had been detected by only one of the five questions; and each of the five questions was the only indicator of at least eight patients with cervical-spine injury and at least five patients with significant cervical-spine injury. Therefore, changing the NEXUS decision instrument by eliminating any one of the criteria would markedly reduce its sensitivity, to the point where it would be unacceptable for clinical use. Thus, all five of these criteria must be met, and, if any one is not met, then cervical x-rays should be performed (Panacek, Mower, Holmes, Hoffman, & NEXUS Group, 2001). The Canadian Cervical Spine Rule The Canadian C-spine Rule (CCR) was derived from a similarly sophisticated multicenter study in which physicians in ten emergency departments in large Canadian community and university hospitals evaluated patients for 20 standardized clinical findings prior to getting neck x-rays. Among 8924 adults who came to the emergency room with blunt trauma to the head or neck, stable vital signs, and a score of 15 on the Glasgow Coma Scale, 151 had significant cervical-spine injury as evaluated by plain radiography, computed tomography, and a structured follow-up telephone interview. Using statistical analysis of the standardized clinical findings, it was determined that the CCR decision tree would have identified every one of these 151 clinically significant cervical-spine injuries (Stiell, Wells, Vandemheen, Clement, Lesiuk, De Maio, et al., 2001). These findings were subsequently evaluated in 7017 alert and stable adult trauma patients at risk for neck injury. More than 350 physicians completed 15-item data forms and interpreted the CCR status for all patients who then had neck x-rays to determine whether they had clinically significant cervical-spine injury. Some patients were independently examined by a second physician, and patients were followed up with a 14-day telephone interview. Among 140 patients with significant cervical-spine injuries, the CCR missed just one – an ambulatory male without midline tenderness, whose initial radiographs were normal, and who was eventually treated with a hard collar. Conclusion: The CCR was reported to be an accurate, reliable, and acceptable decision rule (Stiell, Clement, Wells, McKnight, Brison, Worthington, et al., 2002). Here are the steps of the CCR. STEP 1 The CCR is more complicated than the NLC, and it proceeds in three steps. The first step is to check that the patient matches none of the following high-risk factors:
A dangerous mechanism of injury would be, for example, a fall from an elevation of three feet or higher, bicycle collision, axial load to the head (as when someone dives into an empty swimming pool), or a motor vehicle collision involving high speed, rollover, or ejection. If any one of these high-risk factors is present, then the patient is at risk for having a cervical-spine injury, and a neck x-ray should be performed. STEP 2 However, if none of those three factors is present, then the question is whether the patient is voluntarily able to actively rotate the neck 45 degrees left and right. Whoa! you say; isn’t that risky? Absolutely right. Thus, before any neck rotation test is done, there must first be a finding of at least one low-risk factor on the following list, since their presence indicates a low risk of cervical fracture, thus allowing safe assessment of range of motion:
If none of these criteria is met, don’t even ask the patient to try the neck rotation; just go ahead and get an x-ray. STEP 3 Finally, if any of these criteria is met, then the emergency room doctor can ask the patient to try the neck rotation.
This test, of course, should be done very slowly and carefully, and the patient should stop immediately if there is any pain, or tingling in the extremities, or dizziness, or any other sensation that is out of the ordinary. If the patient can rotate the neck as described, fine; if the patient cannot, then get an x-ray. The ability to rotate the neck as described is a key finding in deciding that a patient is at low risk for cervical-spine injury. One study – involving 8924 alert and stable adult trauma patients at risk for neck injury in 10 tertiary care emergency departments – reported that, in identifying patients at low risk for cervical-spine injury based solely on examining the neck, the most reliable and discriminating neck findings are the ability to actively flex (nod the head up and down), the ability to actively rotate the neck, and absence of midline tenderness. (Stiell, McKnight, Clement, Brison, Lesiuk, Wells, et al., 2002). Comparing the decision rules Which of these decision trees is better? A study comparing the NLC and CCR decision rules has concluded that the CCR decision rules are both more sensitive and more specific than the NLC decision rules. Indeed, as a result of the study, it was reported that the NLC were in fact less sensitive than had previously been reported (Dickinson, Stiell, Schull, Brison, Clement, Vandemheen, et al., 2004). The head-to-head comparison between the NLC and CCR was performed in nine Canadian emergency departments comparing the CCR and NLC as applied to alert patients with trauma who were in stable condition. The CCR and NLC were interpreted by 394 physicians for patients before radiography. Among 8283 patients, 169 had clinically important cervical-spine injuries. The CCR was found to be both more sensitive and more specific than the NLC. Indeed, among the 169 patients with significant cervical-spine injuries, the CCR would have missed one patient, but the NLC would have missed 16 patients with important injuries (Stiell, Clement, McKnight, Brison, Schull, Rowe, et al., 2003). The conclusion? For alert patients with trauma who are in stable condition, the CCR is reportedly superior to the NLC with respect to both sensitivity and specificity for cervical-spine injury. But there is another point to be made. With just five criteria, and no branching decisions, the NLC is simpler and easier to use than the CCR. In fact, physicians reported being less comfortable using the CCR than using the NLC. Tellingly, in the comparative study, for 845 – or ten percent – of the patients, the emergency room doctors simply failed to evaluate range of motion as required by the CCR algorithm (Stiell, Clement, McKnight, Brison, Schull, Rowe, et al., 2003); and, in the follow-up study, doctors misclassified the rule in almost nine percent of the cases, did not evaluate range of motion when indicated in more than 10 percent – yet reported that they were comfortable applying the rule 92.2 percent of the time (Stiell, Clement, Wells, McKnight, Brison, Worthington, et al., 2002). So the lesson is this. The CCR is reportedly a superior instrument, but it is harder to use, and it is easy to use it incorrectly without realizing it. If you use it, especially under conditions of stress, take care to make sure you use it right. Applying the Lessons Can we apply these lessons to the wilderness? If we substitute “immobilize and evacuate” for “get a neck x-ray” in the two decision rules, we can get some guidance about the best way to make a difficult decision in the field. It looks as if the CCR may be more sensitive, catching cervical fractures that the NLC would have missed, but it requires attention to apply correctly. Take into account all the available information. Be careful, be thorough, discuss the options with the patient and the team, and always write down your observations and reasoning. You can’t always make the right decision, but you can still make a good decision. References Dickinson, G., Stiell, I. G., Schull, M., Brison, R., Clement, C. M., Vandemheen, K. L., et al. (2004). Retrospective application of the NEXUS low-risk criteria for cervical spine radiography in Canadian emergency departments. Annals of Emergency Medicine, 43(4), 507-514. Hoffman, J. R., Mower, W. R., Wolfson, A. B., Todd, K. H., Zucker, M. I., & National Emergency X-Radiography Utilization Study Group. (2000). Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. New England Journal of Medicine, 343(2), 94-99. Panacek, E. A., Mower, W. R., Holmes, J. F., Hoffman, J. R, & NEXUS Group. (2001). Test performance of the individual NEXUS low-risk clinical screening criteria for cervical spine injury. Annals of Emergency Medicine, 38(1), 22-25. Stiell, I. G., Clement, C. M., McKnight, R. D., Brison, R., Schull, M. J., Rowe, B. H., et al. (2003). The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. New England Journal of Medicine, 349(26), 2510-2518. Stiell, I. G., Clement, C., Wells, G. A., McKnight, R. D., Brison, R., Worthington, J. R., et al. (2002). Multicenter prospective validation of the Canadian C-spine Rule. Academic Emergency Medicine Volume, 9(5), 359-360. Stiell, I. G., McKnight, R. D., Clement, C., Brison, R., Lesiuk, H., Wells, G. A., et al. (2002). How accurate and reliable is examination of the neck in alert and stable trauma patients? Academic Emergency Medicine, 9(5), 453455. Stiell, I. G., Wells, G. A., Vandemheen, K. L., Clement, C. M., Lesiuk, H., De Maio, V. J., et al. (2001). The Canadian C-spine rule for radiography in alert and stable trauma patients. Journal of the American Medical Association, 286(15), 1841-1848. | ||
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