Assessment of Head Injury Risk Associated With Feet-First Free Falls in 12-Month-Old Children Using an Anthropomorphic Test Device Angela K. Thompson, MEng, Gina Bertocci, PhD, and Mary Clyde Pierce, MD Background: Short distance falls are a common false history provided in cases of child abuse. Falls are also a common occurrence in ambulating young children. The purpose of this study was to determine the risk of head injury in short distance feet-first free falls for a 12-month-old child. Methods: Feet-first free falls were simulated using an anthropomorphic test device. Three fall heights and five surfaces were tested to determine whether chang- ing fall environment characteristics leads to differences in head injury risk out- comes. Linear head accelerations were measured and angular head accelerations in the anterior-posterior direction were determined. Head injury criteria values and impact durations were also deter- mined for each fall. Results: The mean peak linear head acceleration across all trials was 52.2g. HIC 15 values were all below the injury assessment reference value. The mean peak angular head acceleration across all trials was 4,246 rad/s 2 . Impact durations ranged from 12.1 milliseconds to 27.8 mil- liseconds. In general, head accelerations were greater and impact durations were lower for surfaces with lower coefficients of restitution (a measure of resiliency). In falls onto wood and linoleum over con- crete, the ground-based fall was associ- ated with greater accelerations than the two higher fall heights. Conclusions: Results show that fall dynamics play an important role in head injury outcome measures. Different fall heights and impact surfaces led to differ- ences in head injury risk, but the risk of severe head injury across all tested sce- narios was low for a 12-month-old child in feet-first free falls. Key Words: Falls, Child abuse, Head injury, Biomechanics. J Trauma. 2009;66:1019 –1029. C hild abuse is the leading cause of trauma-related fatal- ities in children less than 4 years of age. 1 In the US in 2005, there were approximately 899,000 victims of child abuse. There were also approximately 1,460 fatalities because of child abuse with 76.6% of these cases involving children aged 3 years or less. 2 These numbers may be under- estimated because it has been suggested that as many as 50% to 60% of deaths related to child abuse go unrecorded. 3 Inflicted traumatic brain injury (TBI) is the leading cause of child abuse fatalities. 4–6 In children less than 1 year of age, serious TBI is more likely to be the result of inflicted than noninflicted injury. 5 In children aged 0 to 4, falls are the leading cause of TBI. 7 However, falls are a common false history given by caretakers to cover up inflicted trauma. 8,9 In children aged 0 to 4, approximately 32% of TBI deaths are caused by inflicted trauma, whereas only 3% of TBI deaths are caused by falls. 7 Because short distance falls are a common occurrence in young ambulating children, a clearer understand- ing of the injury potential associated with common fall scenarios could prove useful. Clinicians are commonly asked to determine whether a child’s injuries are consistent with the given cause of the injuries, and the diagnosis of abuse may hinge on this decision. Currently, there is little scientific evidence in the field of injury biomechanics to aid in this decision making. Specific information regarding injury risk associated with common falls falsely reported in child abuse can aid clinicians in distinguish- ing between inflicted and noninflicted injuries. Early detection of abuse may lead to prevention of further escalating injuries and, in some cases, prevent the death of the child. 6 As a first step in understanding the kinematics of simple falls and how they relate to head injury risk, feet-first free falls were experimentally simulated using an instrumented anthropomorphic test device (ATD), or human surrogate, representing a 12-month-old child. Although feet-first falls do not maximize head injury risk, anecdotal evidence indi- cates that feet-first falls are common in young children and have also been given as an explanation of injury causation in child abuse legal cases. The purpose of this study was to investigate the risk of head injury for a 12-month-old child in feet-first free falls and to determine the effect of varying fall height and impact surface on head injury risk. Submitted for publication November 20, 2007. Accepted for publication April 24, 2008. Copyright © 2009 by Lippincott Williams & Wilkins From the Departments of Mechanical Engineering (A.K.T., G.B.), Pediatrics (G.B.), and Bioengineering (G.B.), University of Louisville, Lou- isville, Kentucky; and Children’s Memorial Hospital (M.C.P.), Northwestern University’s Feinberg School of Medicine, Chicago, Illinois. Supported by the Centers for Disease Control: Center for Injury Re- search and Control, University of Pittsburgh as well as the Children’s Hospital of Pittsburgh, Kosair Children’s Hospital (Louisville, KY), and the University of Louisville. Presented at Research Louisville, Louisville, KY, October 2005; Pediatric Academic Society Conference, San Francisco, CA, May 2006; and ASME Engineers Summer Bioengineering Conference, Amelia Island, FL, June 2006. Address for reprints: Angela K. Thompson, MEng, Department of Me- chanical Engineering, University of Louisville, 500 S. Preston Street, Instruc- tional Building B, Room 110, Louisville, KY 40202; email: angela.thompson@ louisville.edu. DOI: 10.1097/TA.0b013e31817dac8b The Journal of TRAUMA  Injury, Infection, and Critical Care Volume 66 • Number 4 1019