The PECARN group has published a set of criteria that identify children at very low risk for significant traumatic injury. This is publicly available and an excellent decision instrument to enhance your clinical judgement. But, the problem is, with excellent sensitivity, the specificity is weak - such that a great number of patients who fail to meet low-risk criteria will still have good outcomes.
So, this is a follow-on study attempting to determine whether the severe mechanism portion of the decision instrument was predictive of significant TBI, or whether scans could be avoided if mechanism was the only positive feature in their decision instrument. And, yes, a severe injury mechanism in isolation - at least in the 35% of their cohort who received a head CT - had only a 0.3% chance of significant injury in age <2 years and 0.6% chance of significant injury in age >2 years. Severe injury mechanisms associated with additional PECARN criteria, however, had 4% and 6% incidence of TBI, depending on age.
Probably the most important aspect of these numbers is they allow for a better discussion of risks with parents and families. While 1 in 150 or 1 in 300 sound like pretty good odds, when you practice long enough, those odds will catch up with you. Even with severe mechanism and additional features, 19 of 20 CTs will be negative - you can still make a reasonable case for observation rather than knee-jerk scanning.
"Prevalence of Clinically Important Traumatic Brain Injuries in Children With Minor Blunt Head Trauma and Isolated Severe Injury Mechanisms"