Correlation of Soft tissue Projection in Injured NEcks (CSPINE) - Prevertebral soft tissue measurement in paediatric cervical spine trauma

Abstract

Background: In paediatric trauma, measured increase in prevertebral soft tissue thickness on a lateral cervical spine (C-spine) X-ray is interpreted as swelling, raising suspicion of C-spine injury. Defining swelling in absolute measurements is cumbersome – children’s sizes vary. Published recommendations are largely lacking in evidence. There may be potentially more consistent tools, for example, to measure soft tissue thickness as a ratio of vertebral body width. The aim of this study was to determine whether consistent, measurable prevertebral soft tissue to vertebral body width ratios exist for use as simple diagnostic tools in the assessment of swelling and injury in paediatric C-spine trauma. Patients and methods: C-spine trauma X-rays taken at a South African children’s hospital were randomly sampled. Seventy-one unintubated X-rays from 85 controls were used to identify normal ratios. The authors measured vertebral bodies and soft tissue at each level, created all possible ratios, then chose the two least variable – one for the upper and one for the lower C-spine. Twenty cases aided in determining diagnostic accuracy for C-spine injury. Results: Mean soft tissue at the second cervical vertebral level (c2) was 38% of the seventh vertebra (C7) (95% confidence interval [CI]: 34–41.9%, standard error [SE]: 2.0%). Mean c6 soft tissue was 65.6% of C7 vertebra (95% CI: 61.9–69.3%, SE: 1.9%). In diagnosing C-spine injury, a receiver operating characteristic (ROC) curve calculation gave an empirical optimal cut-point of 53.9% and 74.4% respectively. Using practical cut-offs of 55% at c2 and 75% at c6 yielded specificities of 93.8% (95% CI: 84.8–98.3%) and 81.8% (95% CI: 70.4–90.2%), with negative predictive values of 90.9% (95% CI: 81.3–96.6%) and 91.5% (95% CI: 81.3–97.2%) respectively. Conclusion: Consistent and specific ratios exist in the upper and lower paediatric C-spine. Both ratios have poor sensitivities and positive predictive values and so are poor screening tools; however, a positive result can raise suspicion of C-spine injury in high-risk individuals. This can help to motivate for further investigations such as computer tomography (CT) or magnetic resonance imaging (MRI), which may not be easily accessible in under-resourced settings. However, further research is required to validate the diagnostic value of these ratios. Level of evidence: Level 4