Understanding Craniofacial Blunt Force Injury: A Biomechanical Perspective

Whittle, K W; Wong, Brittany; Waddell, John Neil; Ichim, Ionut; Swain, Michael; Taylor, Michael; Nicholson, Helen

doi:10.1007/978-1-59745-110-9_3

Cited by 10 publications

(9 citation statements)

References 33 publications

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“…Thus a sharp tip penetrated the skin by wedging open a planar (mode I) crack and a blunt tip penetrated by a ring (mode II) crack. We recently described a simple simulation of blunt force injury in synthetic skin fused to subcutaneous tissue that allowed us to model the skin/subcutaneous complex as an integrated energy absorbing system [15,16]. Our skin/subcutaneous model consisted of a silicone layer fused to a hydrated, open-cell foam.…”

Section: Introductionmentioning

confidence: 99%

Experimental simulation of non-ballistic wounding by sharp and blunt punches

Wong

Ichim

Swain

et al. 2008

Forensic Sci Med Pathol

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Despite a long history of gross and microscopic descriptions of blunt and sharp force injury to the dermal tissues, few have addressed the mechanisms underlying such trauma. The need to develop an understanding of how non-ballistic injury occurs calls for an ability to biomechanically model the process. We recently introduced a basic skin and subcutaneous model, which we used to investigate wounding from a spherical object. Here we employ the same model to examine wounding caused by a sharp wedge shaped object and a blunt rectangular object. Macroscopic examination and SEM views of the surface and cross sections of blunt and sharp force tears show that while in the former there is a clean cut through the skin into the underlying sponge, in the latter there is a tissue plug confined to the skin that is smaller than the impacting rectangle. Fracture initiation in the subdermal tissue occurs at the angles of the impacting object. In sharp force trauma, there is localized breaching of the skin layer coupled with the wedging action of the impacting object. Because the subdermal tissue, in this case the underlying hydrated foam, is attached to the base of the skin, it will contribute to further tearing of the foam beneath the line of contact.

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Section: Introductionmentioning

confidence: 99%

Experimental simulation of non-ballistic wounding by sharp and blunt punches

Wong

Ichim

Swain

et al. 2008

Forensic Sci Med Pathol

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“…These authors used foam-based models and showed that although a sharp tip penetrated the skin by wedging open a planar (mode I) crack, a blunt tip penetrated via a ring (mode II) crack. Recently, we reviewed craniofacial blunt force trauma from a biomechanical perspective, and introduced our own model and its preliminary findings [17]. We concluded that wounding can be modelled in a basic simulation of the contact events during blunt force impact and that these results can be evaluated quantitatively.…”

mentioning

confidence: 98%

The biomechanical modelling of non-ballistic skin wounding: blunt-force injury

Whittle

Kieser

Ichim

et al. 2007

Forensic Sci Med Pathol

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Knowledge of the biomechanical dynamics of blunt force trauma is indispensable for forensic reconstruction of a wounding event. In this study, we describe and interpret wound features on a synthetic skin model under defined laboratory conditions. To simulate skin and the sub-dermal tissues we used open-celled polyurethane sponge (foam), covered by a silicone layer. A drop tube device with three tube lengths (300, 400, and 500 mm), each secured to a weighted steel scaffold and into which a round, 5-kg Federal dumbbell of length 180 mm and diameter 8 cm was placed delivered blows of known impact. To calculate energy and velocity at impact the experimental set-up was replicated using rigid-body dynamics and motion simulation software. We soaked each foam square in 500 mL water, until fully saturated, immediately before placing it beneath the drop tube. We then recorded and classified both external and internal lacerations. The association between external wounding rates and the explanatory variables sponge type, sponge thickness, and height were investigated using Poisson regression. Tears (lacerations) of the silicone skin layer resembled linear lacerations seen in the clinical literature and resulted from only 48.6% of impacts. Poisson regression showed there was no significant difference between the rate of external wounding for different sponge types (P = 0.294) or different drop heights (P = 0.276). Most impacts produced "internal wounds" or subsurface cavitation (96%). There were four internal "wound" types; Y-shape (53%), linear (25%), stellate (16%), and double crescent (6%). The two-way interaction height by sponge type was statistically significant in the analysis of variance model (P = 0.035). The other two-way interactions; height by thickness and sponge type by thickness, were also bordering on statistical significance (P = 0.061 and P = 0.071, respectively). The observation that external wounds were present for less than half of impacts only, but that nearly all impacts resulted in internal wounds, might explain the observed haematoma formation and contusions so often associated with blunt-force injuries. Our study also confirms the key role of hydrodynamic pressure changes in the actual tearing of subcutaneous tissue. At the moment and site of impact, transferred kinetic energy creates a region of high pressure on the fluid inside the tissue. As a result of the incompressibility of the fluid, this will be displaced away from the impact at a rate that depends on the velocity (or kinetic energy) of impact and the permeability and stiffness of the polymeric foam and skin layer.

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“…While a blunt tip penetrates by the growth of a ring (mode II or tearing) crack, a sharp tip wedges open a planar (mode I-opening) crack. They [35] predict that a blunt punch penetrates by an unstable crack advance and results in a compressed column of material at the bottom of the cylindrical cavity thus created. In contrast, the sharp punch tunnels into the tissue at a penetration pressure several times lower than that of a blunt punch.…”

Section: Phillipsmentioning

confidence: 98%

“…Because one of its primary functions is to protect the internal organs from mechanical trauma, skin is viscoelastic with a two-phase response to mechanical force applied to it. This involves, firstly, a viscous component associated with the dissipation of energy and, secondly, an elastic response associated with energy storage [35]. Shergold and Fleck [36] have proposed a simple model of blunt force trauma that can be used to reveal the basic mechanisms that control fracture mechanics of human skin and a simulant (silicone rubber) by developing a micromechanical model for deep penetration of blunt-and sharp-tipped cylindrical punches.…”

Section: Phillipsmentioning

confidence: 99%

Analysis of experimental cranial skin wounding from screwdriver trauma

et al. 2007

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As part of a more extensive investigation of skin wounding mechanisms, we studied wounds created by five common screwdrivers (straight, star, square or Robertson, Posidriv and Phillips) on the shaven foreheads of 12 freshly slaughtered pigs. We fixed the different screwdriver heads to a 5-kg metal cylinder which was directed vertically onto each pig head by a droptube of 700 mm length. We examined skin lesions by photography and also by scanning electron microscopy (SEM). Our evaluation of differences in wound shape and size was based on geometric morphometric methods. Our results show that there are obvious morphological differences between the straight head and the other types. The straight-headed screwdriver penetrates the skin by a mode II crack which results in a compressed skin plug with bundles of collagen fibres forming skin tabs within the actual wound. The sharper-tipped screwdrivers wedge open the skin (mode I), with a clearly defined edge with no skin plugs. Geometric morphometric analysis indicates that shapes of skin wounds created by the five screwdriver types could be classified into three different groups. The straight head results in the most differentiated wound profile, with the Robertson or square and some specimens of star, and also the Posidriv and Phillips giving similar wound outlines. SEM evaluation of wounds created by a new and worn straight-head screwdrivers shows that the outline of the worn screwdriver head is reflected in the shape of the wound it created.

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Understanding Craniofacial Blunt Force Injury: A Biomechanical Perspective

Cited by 10 publications

References 33 publications

Experimental simulation of non-ballistic wounding by sharp and blunt punches

Experimental simulation of non-ballistic wounding by sharp and blunt punches

The biomechanical modelling of non-ballistic skin wounding: blunt-force injury

Analysis of experimental cranial skin wounding from screwdriver trauma

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