Biomechanical implications of low-height falls in toddlers

Published on June 19, 2010 at 6:25 AM · No Comments

An in-depth scientific article published in the July 2010 issue of Journal of Neurosurgery: Pediatrics, entitled Biomechanics of the toddler fall during low-height falls elucidates the impact of head injuries caused by low-height falls in toddlers, using an anthropomorphic biomechanical surrogate. Authors are Nicole G. Ibrahim, PhD, and Susan S. Margulies, PhD, researchers in the Department of Bioengineering at the University of Pennsylvania in Philadelphia. The article is posted online at: http://thejns.org/doi/full/10.3171/2010.3.PEDS09357.

Of the estimated 1.5 million people treated for head injuries every year at U.S. hospital emergency rooms, nearly 380,000 are children ages 4 and younger. Blunt head trauma is commonly encountered by pediatric neurosurgeons and emergency physicians. In children ages 4 and younger, traumatic brain injury (TBI) is the primary cause of fall-related death and severe injury. Although there is a large body of epidemiological work published on falls and injury outcomes, these studies have been greatly limited by a number of factors. "Clinical studies of children injured from falls suggest that fall height and impact surface contribute to injury severity, but there is a lack of agreement on critical fall height and impact conditions, which is why a study in a more controlled environment is crucial," stated Dr. Margulies.

This laboratory recently developed a biofidelic anthropomorphic surrogate for the 6-week-old infant. The current research builds on the infant work utilizing an 18-month-old toddler dummy to investigate the biomechanics of falls in an age group that commonly incurs head injuries from low-height falls. In the toddler surrogate, body weight, body length, and neck stiffness were increased relative to the infant surrogate, including nearly doubling the skull thickness and developing a fused skull to simulate closed sutures and fontanels. The total weight of the dummy was 11 kg to mirror the weight of a 50th percentile 18-month-old toddler.

In this study, the researchers specifically looked at angular motion rather than linear translational head accelerations, because according to existing research, angular motion is more closely associated with TBI. Angular acceleration of the head has been shown to cause stretching and shearing of the underlying vascular and white matter tissue, leading to common clinical manifestations of pediatric TBI such as subarachnoid hemorrhage and diffuse axonal injury.

To simulate falls, the dummy was dropped from 1, 2, and 3 ft heights onto two surfaces (carpet pad and concrete). A total of 60 drops were performed, resulting in 53 successful drops from three heights onto two surfaces.

A typical drop consisted of initial head impact followed by rapid deceleration. An ANOVA was utilized to evaluate the influence of contact surface material and drop height, as well as directional differences in head acceleration response for each drop condition. The following select results were noted:

•Surprisingly, little to no rebound was observed in any scenario, indicating that there was no reversal of direction of the head after the rapid deceleration.

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