Does introduction of a national guideline improve c-spine injury detection?
A wise paediatrician once told me that practicing medicine is part art, part science. Pathology and decision making are not always black and white. Sometimes we have to interpret the grey areas, balancing risk.
Cervical spine injuries in children are rare but missing a c-spine injury has devastating consequences. On the flip side, we are taught to apply the ALARA principle whenever deciding whether a child needs a CT.
ALARA stands for As Low As Reasonably Achievable and is a constant consideration for children whose tissues are very radiosensitive to minimize the lifetime risk of cancer. Obtaining good c-spine x-rays can be tricky and interpreting them requires skill. When managing children with potential for cervical spine injury we ask ourselves does this child need imaging of their c-spine and should it be a CT? In 2014 the National Institute of Health and Care Excellence, NICE, introduced a decision rule to help us select which children need c-spine imaging, and whether it should be by x-ray or CT. This was replicated in the Royal College of Radiology Paediatric Trauma Protocols, published that same year. The guidance describes seven indications for CT, six for CT without an x-ray and the seventh for when there is uncertainty following x-ray:
- Children with a GCS <13 on initial assessment
- A definitive diagnosis of c-spine injury is required
- Other body areas are being scanned for head injury or multi-region trauma
- Focal peripheral neurology
- Paraesthesia in the upper or lower limbs
- 3-view c-spine x-ray demonstrates a significant bony injury, was technically difficult to perform or inadequate, or was normal but with a strong clinical suspicion of injury
NICE describe a caveat to this list: don’t automatically CT a stable child’s c-spine if you’re organising a CT head. NICE recommends the decision for CT versus x-ray should be made on a case-by-case basis after a discussion between a senior ED clinician and senior radiologist. We’ll come back to this later.
Six years on, Catherine Nunn and colleagues have published a paper assessing the impact of the introduction of the NICE c-spine guideline on both the number of c-spine CT scans requested and the number of c-spine injuries diagnosed.
Nunn et al. Have changes in computerised tomography guidance positively impacted detection of cervical spine injury in children? A review of the Trauma Audit and Research Network data. Trauma. 2020 DOI: 10.1177/1460408620939381
What question did the study team ask?
Nunn and her team looked back at data of children under the age of 16 in the Trauma Audit and Research Network (TARN) in two time periods, 2012 – 2013 and 2015 – 2016, to capture a before and after assessment of the NICE guideline. They gathered the following information from the TARN database:
- How many children young people under the age of 16 years had c-spine CT imaging?
- How many had a c-spine injury (CSI)?
- What was the mechanism of injury?
- Was there a different between major trauma centres and trauma units?
A bit about TARN
TARN is a national organisation in the UK, and the biggest trauma registry in Europe, collecting data on moderately and severely injured patients from both major trauma centres (MTCs) and trauma units (TUs). Since its introduction in the 1990s, its data has been integral to quality and research initiatives in trauma care. Patients are included in the registry if they require critical care, are transferred between hospitals for ongoing acute critical care, have a hospital length of stay of more than 3 days or if they die as a result of their traumatic injury. Patients who don’t meet these criteria are not included in the database.
What did the study team find?
Did the NICE guideline increase the specificity of detecting a c-spine injury?
Following the introduction of the NICE guideline, there was a decrease in the proportion of children who had a cervical spine CT, from 13.7% to 12.1%, but this wasn’t a statistically significant drop.
What the team did find was an increase in the rate of injury in the children who were initially imaged with CT, from 10% to 16.4%, meaning the specificity of the selection of children for CT c-spin improved after the introduction of the guideline.
Over 80% of children received high risk radiation to the neck and had no injury. Balancing the risk of radiation against missing an injury continues to be a challenge.
Unsurprisingly, road traffic accident was the most common cause of c-spine injury, followed falls.
What about major trauma centres versus trauma units?
Trauma networks were introduced in the UK a decade ago, dividing regions up into a hub major trauma centre (MTC) with spoke trauma units (TUs). Although MTCs are designated to deliver high-quality specialist trauma care, with efficient pathways getting children to scan as part of more specialized care, severely injured children often present to a TU. Nunn’s team found that the introduction of the NICE guideline was associated with a reduction in the percentage of c-spine scans in both MTCs and TUs: both MTCs and TUs were more selective about which children had a c-spine CT.
Trauma Units were more selective in their choice of children undergoing cervical spine CT with a lower proportion having a CT, but a higher proportion of those scanned having a c-spine injury, meaning there was a higher sensitivity of scan in TUs.
This might reflect the caveat suggested by NICE that we shouldn’t automatically CT a stable child’s c-spine when organising a CT head and the decision in these circumstances should be made on a case-by-case basis. Nunn’s team suggest that the efficiency of MTCs getting patients to scan means that more children are being scanned rapidly (as the pathways intend), but more are scanned who are less likely to be injured (meaning more children are exposed to radiation who don’t have an injury).
Is CT the best imaging modality?
Nunn’s team found that 20% of the CT scans in both time groups were falsely negative. Put another way CT only detected 80% of the c-spine injuries, with the other 20% being picked up on subsequent MRI. SCIWORA, or Spinal Cord Injury Without Radiological Abnormality, is a phenomenon particular to children, who may have spinal cord or ligamentous injury that cannot be seen on x-ray or CT.
Is there a role for MRI instead of CT? MRI is much more sensitive in detecting cord and ligamentous injuries but is logistically challenging because these scans aren’t quick – younger children need sedation or general anaesthetic – and putting severely injured children in an MRI for up to 40 minutes is risky. Nunn’s team suggested there will be times skipping CT altogether and performing a delayed MRI, maintaining c-spine precuations until a child is more stable, might be more practical.
The bottom line
Introduction of a paediatric c-spine CT decision tool had a positive impact. The sensitivity of detecting a c-spine injury increased, and fewer children proportionately had CT scans without injury. Twenty percent of children with c-spine injury had negative CT scans so the question remains, should early MRI be advocated instead of CT in a group of children with suspected injury?