Biomechanics and Injury Assessment of Household Falls in Children
Child abuse is the leading cause of trauma-related fatalities in children less than four years of age. Children aged one year or less are particularly at risk with approximately one out of every 41 children in this age group suffering from abuse. Pediatric short distance falls, especially from beds or other furniture, are a common false history given by caretakers to cover up abusive trauma. In up to 70% of cases of children with abusive injuries, the initial explanation for the injuries given by the caretakers is a fall. However, short distance household falls are also a common occurrence in young children. Knowledge of the types and severity of injuries that can result from these short falls is necessary since clinicians are commonly asked to determine whether a child’s injuries are consistent with the stated cause of the injuries, when attempting to distinguish between inflicted and non-inflicted injuries. Early detection of abuse may lead to prevention of further escalating injuries and, in some cases, prevent the death of the child.
The purpose of this study is to provide objective information about injury risk in short distance falls to aid clinicians in distinguishing between inflicted and non-inflicted injuries in children. This will be accomplished by investigating the injury outcomes and biomechanics associated with common household falls. The specific aims of this study are to determine injury types and severities that are associated with short distance falls from horizontal furniture surfaces (such as a fall from bed, crib, couch, or table) in children ages 0-4, describe fall dynamics and determine biomechanical measures associated with these falls, describe relationships between biomechanical measures and injury outcomes, and to determine whether fall environment factors (height of fall, impact surface), initial position, initial velocity and surrogate characteristics affect the injury outcomes.
This study involves three major methodological components to address the specific aims and obtain a better understanding of injury risk in short distance household falls. The first component is a case-based biomechanical assessment of children who present to the emergency department of a metropolitan children’s hospital with a history of a fall from a bed or other similar furniture. Descriptions of fall dynamics and the fall environment will be obtained through interviews with the caregivers and in-depth scene investigations. The second component utilizes an anthropomorphic test device (ATD), or human surrogate, representing a 12-month-old child, to experimentally simulate falls from furniture surfaces in a laboratory setting. The final component involves development of a validated computer model based upon the ATD experiments. The computer model will extend beyond the experiments by allowing variation in fall parameters and ATD characteristics. In each component, relationships between biomechanical measures and injury outcomes will be investigated.
Click below to see videos of fall experiments and computer simulations.
Improving the Biofidelity of the Hybrid III Three Year Old Anthropomorphic Test Dummy
funded by CDC CIRCL University of Pittsburgh
Falls have been shown to be the most common injury mechanism reported by parents of abused children. Falls are also a common mechanism in unintentional longbone fractures. Longbone fractures have also been shown to be significantly associated with abuse. A scientific, objective method able to evaluate injury risks would greatly aid clinicians and engineers. Knowledge of the loading profiles experienced by longbones prone to fracture during a fall is necessary to determine whether a specific type of fracture could have resulted from a stated fall scenario.
Hybrid III anthropomorphic test dummies (ATDs) were developed to evaluate the safety of occupant protection systems during high energy events, and commonly in motor vehicle crashes. Recently, their use has been extended to evaluating lower energy events even though the biofidelity of the ATD is limited. An ATD model of a three year old child exists and would be a reasonable starting point to increase the biofidelity because of the incidence of abuse and unintentional injury in that age group. A retrofit of the ATD, rather than building a new test dummy, is justified since it already has key features necessary to explore low energy events. These include accurate segment lengths, masses and inertial properties, as well as appropriate stature and geometry. There are, however, areas where the biofidelity must be improved to maximize the benefit of fall investigations. This project focuses on the following objectives:
- Creating bone geometry that better approximates anatomical bone for more realistic force distributions. This will also allow loading measurement at specific bone regions that are prone to fracture.
- Increasing the biofidelity of the soft tissue material properties covering the longbones to better approximate the force attenuation and distribution by the soft tissue.
- Improving the range of motion of the shoulder, knee and hip joints to create more realistic fall dynamics to better capture injury causing events. Currently, the hip and shoulder only have a single degree of freedom that severely limits the fall dynamics and can prevent the arms and legs from reaching positions where injury would have occurred in children experiencing the same fall.
Development of a Classic Metaphyseal Lesion (CML) Biomechanical Model
funded by the US Department of Justice, Office of Juvenile Justice and Delinquency Prevention (Award #2009-DD-BX-0086). The opinions, findings, and conclusions or recommendations expressed in this overview are those of the PI and do not necessarily reflect those of the Department of Justice.
Fractures are the second most common injury resulting from child abuse and are often indicative of escalating violence. The Classic Metaphyseal Lesion (CML), also known as the corner, or bucket-handle fracture, is reported to be highly associated with abusive trauma, although the pathophysiology and biomechanics associated with this fracture type are currently unknown. When a young child or infant presents with a fracture, a determination must be made: how much force did it take to cause this injury and could the scenario provided generate the level of force needed to cause the fracture? Is normal bone present or are there factors that might alter fracture threshold? An inaccurate assessment can result in an abused child being placed back into an unsafe environment, where there is an 80% chance of re-injury and a 10-50% chance of mortality. Conversely, innocent families may be investigated for child abuse and non-abused children may be placed into foster care. Differentiating between accidental and abusive fractures however can be extremely difficult. A current lack of biomechanical understanding of fractures in immature bone and the lack of an objective tool for evaluating bone strength and likelihood of fracture in children makes this determine more difficult.
The goal of this project is to identify loading conditions necessary to create a CML. In order to accomplish this, multiple methodologies will be utilized:
1) Mechanical testing of porcine hind-limb specimens under various loading conditions in an attempt to produce a CML type fracture. All testing will be conducted under the protocol approved by the University of Louisville Institutional Animal Care and Use Committee (IACUC protocol #10154).
2) Finite element analysis to create a virtual bone model that can be used to further investigate the bone's response to loading and fracture development.
3) Development of a synthetic bone surrogate that can replace animal specimens in investigation of pediatric fractures.
Development of a Device to Describe Bruising Patterns Associated with Common Childhood Falls
This project is supported by Award No. NIJ Grant #2008-DD-BX-K311 - awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. The opinions, findings, and conclusions or recommendations expressed in this overview are those of the PI and do not necessarily reflect those of the Department of Justice.
Child abuse is a leading cause of fatality in children 0-4 years of age. Roughly 1500 children fatally injured each year in association with child abuse and 150,000 are permanently disabled. Many of the serious injuries and fatalities could have been prevented if clinicians and child protective services were able to better distinguish between those injuries associated with abuse and those injuries caused by accidents. Clinicians, and child protective services and law enforcement personnel must therefore be equipped with improved knowledge related to the types of injuries that are possible from common household accidents that are often reported to be the underlying cause of injury in child abuse. The ability to detect child abuse at the earliest stages has proven to be critical in the prevention of escalating injury severity and even death. Bruising is an early sign of abuse, and has proven to be an effective indicator and sentinel of child abuse. Moreover, bruising patterns provide a “roadmap” documenting a child’s exposure to impact; information that can be critical in a forensic biomechanical analysis of the child’s injuries.
Our multidisciplinary Injury Risk Assessment and Prevention Laboratory is utilizing state of the art bioengineering techniques to aid clinicians and legal services personnel in distinguishing between abusive and non-abusive injuries. One component of our research relies upon the use of instrumented anthropomorphic test devices, or test dummies, to investigate injury risk in common childhood falls and accidents. We have effectively used these test dummies to investigate head injury and bone fracture risk in children. However, the ability to predict bruising patterns occurring in association with falsely reported events in child abuse does not exist, but could prove extremely useful in the distinction between abusive and accidental injuries in the clinical and medico-legal settings. ***Our study proposes to modify an existing pediatric test dummy to allow for the prediction of potential bruising location, size and patterns in children during common household fall events that are often stated as false scenarios in child abuse. The scope of this project will include the development of a “sensor skin” that will be adapted to a commercial pediatric test dummy. When used in mock laboratory experiments representing common household injury events, the “sensor skin” adapted test dummy will measure and record levels of impact force and locations of impact encountered by the human surrogate. Data from the sensors will be acquired and compiled in a computerized visual body map image displaying the areas of contact or impact that represent potential bruising or soft tissue injury. This body map image will then provide a “roadmap” of the human surrogate’s exposure during a specific event and will define a compatible bruising roadmap-specific event combination. A database of bruising roadmap-event combinations will ultimately be developed for various common household falls. The “bruising roadmaps” will be available as a tool in suspected child abuse cases where bruising exists as an aid in determining whether presenting soft tissue injuries are compatible with the stated cause.