Determination of the Material Properties of the Pediatric Rib

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URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1392019115

Abstract

Understanding the characteristics of the pediatric chest is of great importance for analyzing pediatric traumatic injury. As indicated by the increase in fatalities when thorax injury is accompanied with head and abdominal injuries, there is a correlation between the behavior of the thorax and the head. The initial motion of the thorax dictates the relative movement of the top of the spine, neck, and head. Also, the deflection of the pediatric rib cage may result in internal injuries to the abdomen and chest cavity without rib fracture. In order to realize the potential for internal injuries without visible rib fracture, the behavior of the pediatric thorax must be determined. The literature contains much data on the adult rib, but properties of the pediatric rib are lacking from previous studies. Due to the extreme differences in growth and development between children and adults, the scaling of adult properties to reflect those of children based strictly on size is not reasonable. Several other factors, including fracture mechanisms and bone development, must be taken into account.

The objective of this study is to determine the material properties of the excised pediatric rib as a function of age and to compare the results to the material properties of the excised porcine rib. A total of 150 porcine rib samples from 25 porcine subjects, and 31 rib samples from 9 pediatric subjects were loaded in 3-point bending at a quasi-static rate. All data were analyzed for rotation during testing, axis of moment of inertia, stiffness, Young’s modulus, flexural rigidity, peak force, bending strength, yield force, and yield stress.

The results of the study indicate that the rib cross-section undergoes minimal rotation during testing. However, the orientation of the bending axis does not always correspond to the orientation of the principal axis of the minimum moment of inertia. For the porcine subjects, moment of inertia, stiffness, flexural rigidity, peak force, and yield force showed a linear increase with age. The variables of Young’s modulus, bending strength, and yield stress are believed to be constant over all ages of porcine subjects. All variables analyzed for 3-point bending of the pediatric rib showed increase in value as a function of pediatric age.

The major finding of this study is that porcine subjects do not present an acceptable animal model for the behavior of the pediatric rib. Development rates between humans and the pig are vastly different. The conclusion from this study is that additional pediatric rib specimens are needed in order to fully understand the changes in the material properties of the pediatric rib as a function of age.

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Cited By (3)

Year	Entry
2007	Pfefferle KL, Litsky A, Donnelly B, Bolte J IV. Biomechanical properties of the excised pediatric human rib. In: Proceedings of the 35th International Workshop on Human Subjects for Biomechanical Research. 2007.142-156.
2014	Schafman M, Kang Y-S, Moorhouse K, Agnew AM. The effect of age on the structural properties of ribs in dynamic frontal loading. In: Proceedings of the 10th Ohio State University Injury Biomechanics Symposium. May 18-20, 2014; Columbus, OH.
2015	Agnew AM, Schafman M, Moorhouse K, White SE, Kang Y-S. The effect of age on the structural properties of human ribs. J Mech Behav Biomed Mater. January 2015;41:302-314.