Biomechanics of Frontal Skull Fracture

Abstract

The purpose of the present study was to investigate whether an energy failure level applies to the skull fracture mechanics in unembalmed post-mortem human heads under dynamic frontal loading conditions. A double-pendulum model was used to conduct frontal impact tests on specimens from 18 unembalmed post-mortem human subjects. The specimens were isolated at the occipital condyle level, and pre-test computed tomography images were obtained. The specimens were rigidly attached to an aluminum pendulum in an upside down position and obtained a single degree of freedom, allowing motion in the plane of impact. A steel pendulum delivered the impact and was fitted with a flat-surfaced, cylindrical aluminum impactor, which distributed the load to a force sensor. The relative displacement between the two pendulums was used as a measure for the deformation of the specimen in the plane of impact. Three impact velocity conditions were created: low (3.60+/-0.23 m/sec), intermediate (5.21+/-0.04 m/sec), and high (6.95+/-0.04 m/sec) velocity. Computed tomography and dissection techniques were used to detect pathology. If no fracture was detected, repeated tests on the same specimen were performed with higher impact energy until fracture occurred. Peak force, displacement and energy variables were used to describe the biomechanics. Our data suggests the existence of an energy failure level in the range of 22-24 J for dynamic frontal loading of an intact unembalmed head, allowed to move with one degree of freedom. Further experiments, however, are necessary to confirm that this is a definitive energy criterion for skull fracture following impact.

Biofidelic neck influences head kinematics of parietal and occipital impacts following short falls in infants

“…traumatic axonal injury and intracranial hemorrhage), focal contusions, and skull fracture. (Gennarelli, Thibault et al 1982, Raghupathi and Margulies 2002, Yoganandan and Pintar 2004, Delye, Verschueren et al 2007, Monea, Van der Perre et al 2014) Therefore, a detailed understanding of the biomechanics of low height falls can help distinguish between accidental fall and abusive head injury etiologies.…”

Development of a Human Cranial Bone Surrogate for Impact Studies

“…This was typical of failures seen in either of the materials made with the U.S. Foam 16# core, i.e., B or C. The types of linear ductile cracks seen match those seen in pendulum impacts of skulls from Gurdjian et al (1950) and Delye et al (2007). However, the types of fractures produced in using BIB-TC 812 foam resulted in a brittle type of fracture as shown in Figure 7.…”

“…The variance may be due to a number of things, among them, the processing and molding of the samples, the adherence of the surrogate cranial tables to the diplöe and the type of fractures that are initiated in the surrogate cranial tables. The average force to fracture of all materials in the flat plates in the drop tower test was 1650 N, which considerably lower than the average force to fracture an intact human skull in both the protected and unprotected configuration under impact conditions that vary from drop tower to ballistic impact (Nahum et al, 1968; Melvin et al, 1969; Hodgson et al, 1970; Hubbard, 1971; Schneider and Nahum, 1972; Yoganandan et al, 1995; Sarron et al, 2004; Hart, 2005; Delye et al, 2007; Verschueren et al, 2007; Raymond et al, 2009). This number was 7055 ± 4070 N and depended on the nature of tissue preparation (embalmed or fresh), the geometry of the impactor, the rates of impact and what the region of the skull was being impacted.…”

“…A number of studies have been performed using post-mortem human surrogate (PMHS) specimen to study the effect of blunt impact on pressures and displacements in the brain (Hardy et al, 1997, 2001), determine skull failure thresholds and characterize skull fracture patterns (Gurdjian et al, 1949; Melvin et al, 1969; Hodgson et al, 1970; Schneider and Nahum, 1972; Sarron et al, 2004; Hart, 2005; Delye et al, 2007; Verschueren et al, 2007; Raymond et al, 2009). Due to the complexity of these PMHS experiments along with the inherent likelihood of significant specimen variability, it would be prudent to have a skull surrogate which can represent the stress, vibration, and fracture characteristics of human cranial bone in a repeatable manner.…”

Does facial soft tissue protect against zygomatic fractures? Results of a finite element analysis

“…Our measurement of 3 to 4 mm scalp thickness derived from an automatic software-based calculation corresponds well to data taken from literature and measurements performed on the CT-scan [30, 31]. Additionally, facial soft tissues were modelled as one material and was not divided into skin, fat, and muscle.…”