Answer: F
Dangerous mechanism is a criteria of the Canadian C-Spine Rule, not the NEXUS.
Patients who are awake and alert can reliably be cleared of cervical spine pathology by painless clinical examination alone. While a missed cervical spine injury can be devastating, chronic use of cervical collars is equally detrimental with the development of skin breakdown and ulceration.
The National Emergency X-Radiography Utilization Study (NEXUS) was a prospective, observational study involving 21 centers across the United States that evaluated 34,069 stable patients with blunt trauma who were at risk for cervical spine injury. The presence of any one of the findings above implied that the patient was at increased risk for a cervical spine injury and required radiographic evaluation. The decision instrument had a sensitivity of 99.6%, a NPV of 99.9%, a specificity of 12.9%, and a PPV of 2.7% for the identification of clinically significant cervical spine injuries.
Another instrument is the The Canadian C-Spine Rule. When retrospectively applied to the population from which it was derived, the decision instrument had a sensitivity of 100%, a NPV of 100%, a specificity of 42.5% and a PPV of 2.9% for the identification of clinically significant cervical spine injuries. When prospectively applied to a separate population of 7,438 alert and stable patients, the decision instrument had a sensitivity of 99.4%, NPV of 99.97%, a specificity of 45.1%, a PPV of 3.9% for the identification of clinically significant cervical spine injuries.
References
1. Hoffman JR et al. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. N Engl J Med 2000; 343:94-99.
2. Stiell IG et al. The Canadian C-spine rule for radiography in alert and stable trauma patients. JAMA 2001; 286:1841-1848.
3. Stiell IG et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med 2003; 349:2510-2518.
4. Cervical Spine Clearance
5. Cervical Spine Clearance