Clearing a Trauma Patient from Imaging
For alert, evaluable trauma patients, use clinical decision rules (NEXUS or Canadian C-Spine Rule) to determine if imaging is needed; for obtunded blunt trauma patients, multidetector CT (MDCT) of the entire spine with submillimeter cuts (<3mm) is the primary clearance modality, and MRI should be reserved only for patients with neurological deficits referable to the spine. 1, 2
Alert, Evaluable Patients
Clinical clearance without imaging is appropriate when ALL of the following preconditions are met: 1
- GCS 15 and fully alert 1
- No intoxicants present 1
- No neck pain or tenderness 1
- No distracting injuries 1
- Moving all four limbs normally 1
If any precondition fails, proceed to imaging with MDCT of the entire spine. 1
Obtunded Blunt Trauma Patients (OBTPs)
Primary Imaging: MDCT Protocol
MDCT of the entire spine is the definitive clearance modality for obtunded patients, with sensitivity approaching 100% for detecting unstable bony injuries. 1, 2
Technical requirements for adequate MDCT: 2
- Complete visualization from skull base through C7-T1 junction 2
- Axial slice thickness <3mm (ideally 1.5-2mm) 2
- Sagittal and coronal reconstructions mandatory 2
Critical pitfall: Plain radiographs are inadequate and dangerous, missing approximately 15% of cervical injuries, with the cervicothoracic junction not visualized in up to 49% of cases. 2
Thoracolumbar Spine Clearance
CT is superior to plain imaging for thoracolumbar spine with 100% sensitivity and 97% specificity versus 73% sensitivity for plain films. 1
- If CT chest/abdomen/pelvis (CT-CAP) already performed, use reformats for thoracolumbar evaluation 1
- Evaluate entire spine when any fracture identified, as 16% have non-contiguous fractures 1
- Do not perform plain radiographs of thoracolumbar spine in obtunded patients 1
MRI Considerations: When and Why Not
MRI should be obtained ONLY in obtunded patients with neurological deficits referable to the spine (weakness, sensory changes, or myelopathy). 1
The case against routine MRI after normal CT: 1
- MRI after normal CT detects additional findings in 7.5% of patients 1
- Only 0.29% require operative intervention 1
- 4.3% receive prolonged collar application 1
- False positive rate is 25-40%, with many findings representing clinically insignificant variations 1
- No established criteria exist to distinguish significant from inconsequential MRI abnormalities 1
The risk-benefit calculation: Isolated ligamentous injury in blunt polytrauma ranges from only 0.1-0.7% (consistently under 1%), while prolonged immobilization causes significant morbidity. 1, 2
Obsolete Modalities
Dynamic fluoroscopy and flexion-extension radiography should not be used: 1, 2
- Ability to visualize relevant anatomy is poor (as low as 4%) 1
- Low ability to detect injury 1
- Number needed to treat is 295-500 to detect significant injuries 2
- Highly resource and labor intensive 1
Morbidity of Prolonged Immobilization
Remove spinal precautions as soon as imaging clearance is achieved because complications escalate rapidly after 48-72 hours: 2
- Pressure sores 2
- Increased intracranial pressure 2
- Life-threatening airway complications 2
- Aspiration pneumonia 2
- Thromboembolic events 2
Critical consideration: In a population where 95% have no actual spinal injury, the secondary morbidity and mortality from prolonged immobilization can rival the complication rates from missed injuries. 1
Practical Algorithm Summary
Alert patient with GCS 15, no intoxicants, no neck signs, no distracting injuries: Clinical clearance without imaging 1
Obtunded patient OR alert patient failing clinical criteria: MDCT entire spine with <3mm cuts and multiplanar reconstructions 1, 2
Neurological deficit present in obtunded patient: Add MRI after MDCT 1
Normal MDCT in obtunded patient without neurological deficit: Remove spinal precautions; do not obtain routine MRI 1
Any fracture identified: Evaluate entire spine for non-contiguous injuries 1