The National Emergency X-Radiography Utilization Study (NEXUS) Criteria were developed to help clinicians determine whether or not cervical spine imaging can be safely avoided in appropriate patients.
The validation study included a prospective, observational sample of 34,069 patients, aged 1 to 101 years, presenting to 21 trauma centers in the United States. Among the patients studied, 1.7% had clinically significant cervical spine injuries (CSIs). The NEXUS criteria were found to have sensitivity of 99.6% for ruling out CSIs. The study also detected 99% of all CSIs–all but 8 of 818 patients, among whom 6 had injuries that didn’t require stabilization or specialized treatment In the study, adoption of the criteria could have decreased imaging in patients with cervical spine injuries by 12.6%. Subsequent studies have found a sensitivity of 83% to 100% for CSI, with the majority of studies finding 90% to 100% sensitivity.
Unlike the Canadian C-Spine Rule (CCR), the NEXUS Criteria do not have age cutoffs and are theoretically applicable to all patients aged >1 year. However, some literature suggests the use of caution in applying NEXUS Criteria to patients aged >65 years, as the sensitivity may be as low as 66% to 84%. In a large, retrospective trauma registry study of 231,018 patients, sensitivity was still only 94.8% (95% confidence interval, 92.1%-96.7%) (Paykin 2017).
In the only trial to undertake a prospective head-to-head comparison of the NEXUS Criteria and the CCR, the CCR was found to have superior sensitivity (99.4% vs 90.7%). However, the trial was performed by the creators of the CCR at hospitals that were involved in the initial CCR validation study (Stiell 2003). There were also post hoc clarifications added by the authors to the original NEXUS Criteria, leading to some concerns about the generalizability of the study findings. There is also debate about whether x-rays of the cervical spine are sufficiently sensitive to rule out cervical spine injuries in trauma patients, and whether computed tomography (CT) is a more appropriate imaging modality in this patient population.
Because of concerns that the NEXUS Criteria do not perform as well among patients aged >65 years, clinicians may want to consider further imaging if there is concern about the mechanism or examination in elderly patients. Although more complicated to remember, the CCR appears to perform as well or better than NEXUS in terms of sensitivity for CSI. In cases where a patient is not ruled out by the NEXUS Criteria, it may be appropriate to apply the CCR. If the patient is negative for the CCR, then further imaging is probably unnecessary; for example, patients with midline cervical spine tenderness would need imaging according to the NEXUS criteria, but potentially could be cleared by the CCR if they did not have any high-risk features and could range their necks 45 degrees to the left and right.
There is also concern that the NEXUS Criteria were derived and validated in an era when plain films were much more commonly ordered to assess for cervical spine injuries. CT imaging of the cervical spine is now more common, and there is some evidence that CT may identify CSIs that would be missed by NEXUS and/or the CCR.
Daniel Runde, MD
At 34,069, the number of patients enrolled in the original validation study for the NEXUS Criteria was over 3.5 times greater than in the original CCR study. As applied, the rule missed 2 of the 578 patients with a clinically significant CSI, yielding a sensitivity of 99.6% (Hoffman 1998). Subsequent evaluations of the NEXUS Criteria have found the sensitivity for CSI to be more variable (83%-100%), but there have been some concerns about the methodology (retrospective review) and the way the criteria were applied in several of these analyses. In a trial in which all patients underwent CT imaging of their cervical spine, the NEXUS Criteria was found to have a sensitivity of 83%, with the rule missing 2.5% of patients with fractures (26 of 1057). Sixteen (1.5%) of these patients required prolonged time in a cervical collar, 2 (0.2%) underwent operative repair, and 1 (0.1%) had a halo placed. A retrospective analysis attempting to apply the NEXUS Criteria to the validation cohort for the CCR found a sensitivity of 92.7%.
Jerome Hoffman, MD
The Canadian C-spine rule (CCR) was developed to help clinicians determine which trauma patients need cervical spine imaging. The CCR is highly sensitive for cervical spine injury, with most studies finding that it catches 99% to 100% of these types of injuries. Applying the CCR allows emergency clinicians to safely decrease the need for imaging among the trauma patient population by >40%. Subsequent studies have found a sensitivity of 90% to 100% for cervical spine injury, with the majority finding 99% to 100% sensitivity.
The CCR is difficult to memorize due to its multiple criteria; using a smartphone app or digital reference is recommended. It can be used in patients who are intoxicated if the patient is alert and cooperative, regardless of blood alcohol level. The quoted sensitivities are all for cervical spine injury. Some practice environments might be concerned with identifying any cervical spine injury, as the CCR is highly sensitive for clinically important cervical spine imaging.
The lone trial with a sensitivity of 90% was a study in which nurses were trained to apply the CCR; retrospective review by investigators in this study found the rule was misapplied in 4 cases with obvious high-risk features. The CCR has also been successfully evaluated in paramedics.
If a patient has any high-risk factors (eg, aged >65 years, a defined dangerous mechanism, or paresthesias in the arms or legs) then cervical spine imaging is required. Cervical spine imaging is required if a patient has no high-risk factors but meets none of the defined low-risk criteria (eg, sitting position in the emergency department, ambulatory at any time, delayed [not immediate onset] neck pain, no midline tenderness, simple rear-end motor vehicle collision [excludes pushed into traffic, hit by bus/ large truck, rollover, or hit by high-speed vehicle]). If a patient has no high-risk factors and has neck pain, but meets even 1 low-risk factor, then it is safe to assess the patient's ability to rotate the neck 45 degrees to the left and right. If the patient can do this (even with some pain or discomfort), then no further imaging is required; if not, then cervical spine imaging is indicated.
Exclusion criteria for the Canadian C-Spine Rule:
Daniel Runde, MD
In the derivation study, the authors looked at the primary endpoint of clinically significant cervical spine injury. The validation study included a convenience sample of 8924 patients, aged 16 to 64 years, who presented to 10 Canadian trauma centers with stable vital signs and a Glasgow coma scale score of 15. Among the study population, 1.7% of patients had clinically significant cervi-cal spine injury. The CCR was found to be 100% sensitive for ruling out cervical spine injury (defined as any fracture, dislocation, or ligamentous injury). Researchers also detected 96.4% (27 of 28) cervical spine injuries that were clinically insignificant (defined as injuries that do not require stabilization or specialized treatment and are unlikely to cause any long-term problems).
Ian Stiell, MD, MSc, FRCPC
The Injury Severity Score (ISS) was initially derived in patients with blunt traumatic injury from motor vehicle accidents. The ISS is not intended to be used for bedside decision-making for a single patient in the emergency department setting, but rather as a tool to standardize the study of trauma patients. Due to the nature of the score, multiple combinations of Abbreviated Injury Scale (AIS) scores may result in the same ISS, each of which may indicate a different mortality rate. For example, an ISS of 17 can be calculated from patients with a combination of points based on the 3 most severe injuries, such as (4, 1, 0) or (3, 2, 2). The ISS assigns equal value to each body region.
In all trauma patients, the initial treatment strategy should focus on the primary and secondary survey, and assessing and stabilizing the patient. Although the ISS is intended primarily for research purposes, it may have broader clinical use in the intensive care unit for prognostication following the initial stabilization of traumatic injuries.
Max Berger, MD
Alexandra Ortego, MD
First, the most severe injury from each of 6 body systems is assigned an AIS score on a scale of 0 (no injury) to 6 (unsurvivable injury). Next, those scores are used to determine the 3 most injured body systems. Finally, the ISS is calculated by squaring the AIS score for each of the 3 most injured body systems, then adding up the 3 squared numbers (A2 + B2 + C2 = ISS, where A, B, and C are the AIS scores of the most severe injury in each of the 3 most severely injured body systems). Patients with an AIS of 6 in any body system are automatically assigned an ISS of 75, the maximum possible score.
The ISS is used primarily in research settings, so calculation of the score should not delay initial management of patients with traumatic injuries.
The ISS was derived by Baker et al (1974) by taking the previously used AIS (American Medical Association Committee on Medical Aspects of Automotive Safety 1971) and adding the squared value of each of the 3 most severely injured body systems, in an effort to add increasing importance to the most severe injuries. The top 3 most severe injuries were used to calculate the final score because it had been shown that injuries that would not necessarily be life-threatening in isolation could have a significant effect on mortality when they occurred in combination with other severe injuries. The derivation study included only injuries sustained from motor vehicle collisions, including the occupants of the vehicles and any pedestrians involved.
Further studies have validated the ISS to include other mechanisms of injury. A study by Beverland et al (1983) of 875 patients with gunshot wounds showed that an increasing ISS was associated with increasing mortality (chi-squared = 83.31, P < .001). A study by Bull (1978) confirmed the correlation between increasing ISS and increasing mortality in road traffic accidents, and showed correlation be-tween increasing ISS and increasing mean hospital length of stay.
In a study of 8852 trauma patients from the Illinois Trauma Program (including both vehicular and nonvehicular trauma), Semmlow et al (1976) had similar findings to Baker et al regarding the relationship between ISS and mortality. They also found that the ISS correlated with hospital length of stay.
Susan P. Baker, MPH
Karen Lind, MD, MACM, FACEP; Amy Do-Nguyen, MD
Michael P. Jones, MD, FACEP; Leslie V. Simon, DO, FACEP
April 15, 2021