Head Kinematics Associated with Short Falls in Children
John D. Lloyd, Ph.D., M.Erg.S., CPE, CBIS
Board Certified Ergonomist | Certified Brain Injury Specialist
32824 Michigan Avenue, San Antonio, FL 33576
Tel: (813) 624-8986
This study involved systematic assessments of falls from heights ranging from 2 to 6 ft onto varying flooring surfaces including concrete, linoleum, apartment grade carpeting with underlay, berber carpet with underlay, commercial carpeting without pad, and wood laminate.
A CRABI-12 biofidelic mannequin (29.5 in / 22lb), calibrated and certified by Denton ATD, Inc. and a Hybrid III-3 year old (37.2in / 35.65lb) biofidelic mannequin, calibrated and certified by Key Safety Systems, Inc. were used during this systematic evaluation of short falls.
A tri-axial piezo-electric accelerometer, was installed at the center of mass of the headforms, in accordance with convention described in SAE J211. Still photography and high-speed video (240Hz) was used to record the fall sequences.
A height adjustable platform was used to represent the fall surface. The platform has trap-doors which are held in place by electromagnets. Interruption of power to the electromagnets causes the sprung trapdoors to open instantaneously, thereby initiating the fall sequence. One-hundred-and-seventy-five trials were completed to investigate biomechanical mechanisms of injury associated with short falls in children.
Data from the tri-axial piezo-electric accelerometer, mounted in the head of the biofidelic mannequin were acquired at a rate of 10,000 samples per second using LabView software. Data were analyzed using MatLab, including Fast Fourier Transform analysis to visualize the frequency spectrum of the data, followed by phase-less filtering using a 4th order low-pass Butterworth filter with a cut off frequency of 1650Hz (per SAE J211).
The peak magnitude value of head linear acceleration components was calculated and presented in G’s. This value was then used to compute Head Injury Criterion values.
As anticipated, the larger Hybrid III 3-year old biofidelic mannequin generated higher linear accelerations, HIC values and forces upon impact associated with short falls. Interestingly, both the CRABI12 infant-representative and Hybrid III toddler representative exceeded injury threshold values from a fall height of only 2 feet (61 cm), based on peak magnitude linear acceleration and Head Injury Criterion, which indicates that such short falls can cause substantial head / brain injuries in young children.