Falls are the most common unintentional injury modality among infants, as well as the most common history provided by caretakers in cases of suspected child abuse. Skull fracture is a common finding for both violence-related and unintentional head injuries, and it is not clear what fall heights cause skull fracture in young children.
Material property testing of human infant skull and suture, anthropomorphic surrogate simulations, and finite element modeling were combined to determine the fall heights capable of creating skull fracture. The ultimate stress of human adult cranial bone at high test rates is more than 5 times higher than pediatric cranial bone, indicating a lower threshold for fracture. However, adult cranial bone was found to be 48 times stiffer than pediatric cranial bone, and pediatric cranial suture was able deform over 100% before failure, producing an infant skullcase that may significantly deform before fracture, increasing the potential for brain deformation and injury upon impact.
Angular accelerations calculated from surrogate simulations of head-first falls from 1-3 feet reveal that drops onto mattress produce significantly lower rotational accelerations than carpet and concrete. Drops onto carpet pad were not significantly different than concrete due to compression of the carpet pad and underlying concrete surface. Sagittal and axial rotation accounted for the majority of head motion during all drops.
Using measured material property data and loads from the surrogate simulations, a 3D finite element model of a 1-½ month old infant head predicted that a 280 N impact force onto the occiput would result in a 50% probability of skull fracture in infants. Based on the range of forces calculated for the fall simulations of average head-first impacts, we conclude that there is ≥ 50% probability of skull fracture in infants with head-first impact to the occiput from falls of 1-3 feet onto carpet pad and concrete, but not onto a mattress.
By defining biomechanical tolerances of pediatric tissues and mechanisms of injury, better accident prevention methods may be developed, and clinicians will be better equipped to make objective assessments of injury etiologies in infants.
|1969||Burdi AR, Huelke DF, Snyder RG, Lowrey GH. Infants and children in the adult world of automobile safety design: pediatric and anatomical considerations for design of child restraints. J Biomech. July 1969;2(3):267-280.|
|1982||Gennarelli TA, Thibault LE, Adams JH, Graham DI, Thompson CJ, Marcincin RP. Diffuse axonal injury and traumatic coma in the primate. Ann Neurol. 1982;12(6):564-574.|
|1971||Wood JL. Dynamic response of human cranial bone. J Biomech. 1971;4(1):1-2.|
|1991||Ruan JS, Khalil T, King AI. Human head dynamic response to side impact by finite element modeling. J Biomech Eng. August 1991;113(3):276-283.|
|1996||Ruan JS, Prasad P. Study of the biodynamic characteristics of the human head. In: Proceedings of the 1996 International IRCOBI Conference on the Biomechanics of Impact. September 11-13, 1996; Dublin, Ireland.63-74.|
|2000||Margulies SS, Thibault KL. Infant skull and suture properties: measurements and implications for mechanisms of pediatric brain injury. J Biomech Eng. August 2000;122(4):364-371.|
|2006||Coats B, Margulies SS. Material properties of human infant skull and suture at high rates. J Neurotrauma. August 2006;23(8):1222-1232.|
|1980||McPherson GK, Kriewall TJ. The elastic modulus of fetal cranial bone: a first step towards an understanding of the biomechanics of fetal head molding. J Biomech. 1980;13(1):9-16.|
|1995||Meaney DF, Smith DH, Shreiber DI, Bain AC, Miller RT, Ross DT, Gennarelli TA. Biomechanical analysis of experimental diffuse axonal injury. J Neurotrauma. November 1995;12(4):689-694.|
|2002||Kleiven S, von Holst H. Consequences of head size following trauma to the human head. J Biomech. 2002;35(2):153-160.|
|1972||Shuck LZ, Advani SH. Rheological response of human brain tissue in shear. J Basic Eng. December 1972;94(4):905-911.|
|1966||Sedlin ED, Hirsch C. Factors affecting the determination of the physical properties of femoral cortical bone. Acta Orthop Scand. 1966;37(1):29-48.|
|1989||Hosmer DW Jr, Lemeshow S. Applied Logistic Regression. New York, NY: John Wiley & Sons; 1989.|
|1999||Willinger R, Kang H-S, Diaw B. Three-dimensional human head finite-element model validation against two experimental impacts. Annals Biomed Eng. May–June 1999;27(3):403-410.|
|1968||Ommaya AK. Mechanical properties of tissues of the nervous system. J Biomech. 1968;1(2):127-136.|
|1995||Yoganandan N, Pintar FA, Sances A Jr, Walsh PR, Ewing CL, Thomas DJ, Snyder RG. Biomechanics of skull fracture. J Neurotrauma. August 1995;12(4):659-668.|
|1970||Timoshenko SP, Goodier JN. Theory of Elasticity. 3rd ed. New York, NY: McGraw-Hill Book Co; 1970.|
|2002||Hilker CE, Yoganandan N, Pintar FA. Experimental determination of adult and pediatric neck scale factors. Stapp Car Crash J. 2002;46:417-429. SAE 2002-22-0020.|
|2002||Nuckley DJ, Hertsted SM, Ku GS, Eck MP, Ching RP. Compressive tolerance of the maturing cervical spine. Stapp Car Crash J. 2002;46:431-440. SAE 2002-22-0021.|
|2004||Prange MT, Luck JF, Dibb A, Van Ee CA, Nightingale RW, Myers BS. Mechanical properties and anthropometry of the human infant head. Stapp Car Crash J. 2004;48:279-299. SAE 2004-22-0013.|
|2002||Prange MT, Margulies SS. Regional, directional, and age-dependent properties of the brain undergoing large deformation. J Biomech Eng. 2002;124(2):244-252.|
|2001||Bilston LE, Liu Z, Phan-Thien N. Large strain behaviour of brain tissue in shear: some experimental data and differential constitutive model. Biorheology. 2001;38(4):335-345.|
|2002||Klinich KD, Hulbert GM, Schneider LW. Estimating infant head injury criteria and impact response using crash reconstruction and finite element modeling. Stapp Car Crash J. 2002;46:165-194. SAE 2002-22-0009.|
|1970||Galford JE, McElhaney JH. A viscoelastic study of scalp, brain, and dura. J Biomech. 1970;3(2):211-221.|
|1984||Pelker RR, Friedlaender GE, Markham TC, Panjabi MM, Moen CJ. Effects of freezing and freeze‐drying on the biomechanical properties of rat bone. J Orthop Res. 1984;1(4):405-411.|
|2003||Pellman EJ, Viano DC, Tucker A, Casson IR, Waeckerle JF. Concussion in professional football: reconstruction of game impacts and injuries. Neurosurgery. October 2003;53(4):799-814.|
|1976||McElhaney JH, Roberts VL, Hilyard JF. Handbook of Human Tolerance. Tokyo, Japan: Japan Automobile Research Institute (JARI) Inc; 1976.|
|1970||McElhaney JH, Fogle JL, Melvin JW, Haynes RR, Roberts VL, Alem NM. Mechanical properties of cranial bone. J Biomech. 1970;3(5):495-511.|
|2013||Rangarajan N, DeRosia J, Humm J, Thomas D, Cox J. An improved method to calculate paediatric skull fracture threshold. In: Proceedings of the 23rd International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 27-30, 2013; Seoul, South Korea.|
|2017||Rangarajan N, Shams T, Fukuda T. Probability model relating contact velocity and pediatric head injury severity. In: Proceedings of the 25th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 5-8, 2017; Detroit, MI.|
|2017||Rangarajan N, Shams T, Carole J, Fukuda T. Probability of pediatric skull fracture at various contact velocities. In: Proceedings of the 25th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 5-8, 2017; Detroit, MI.|
|2019||Rangarajan N. Hertz contact model to estimate pediatric head impact response variables. In: Proceedings of the 26th International Technical Conference on the Enhanced Safety of Vehicles (ESV). June 10-13, 2019; Eindhoven, Netherlands.|
|2010||Loyd AM, Nightingale R, Bass CRD, Mertz HJ, Frush D, Daniel C, Lee C, Marcus JR, Mukundan S, Myers BS. Pediatric head contours and inertial properties for ATD design. Stapp Car Crash J. 2010;54:167-196. SAE 2010-22-0009.|
|2016||Pasquesi SA. Can Vigorous Shaking Cause Extra-Axial Hemorrhage in Newborns? A Detailed Human and Porcine Study [PhD thesis]. Philadelphia, PA: University of Pennsylvania; 2016.|