Emily R Streetman

The role of impact interface characteristics on the biomechanics and patterns of cranial fracture has not been investigated in detail, and especially for the pediatric head. In this study, infant porcine skulls aged 2–19 days were dropped with an energy to cause fracturing onto four surfaces varying in stiffness from a rigid plate to one covered with plush carpeting. Results showed that heads dropped onto the rigid surface produced more extensive cranial fracturing than onto carpeted surfaces. Contact forces generated at fracture initiation and the overall maximum contact forces were generally lower for the rigid than carpeted impacts. While the degree of cranial fracturing from impacts onto the heavy carpeted surface was comparable to that of lower-energy rigid surface impacts, there were fewer diastatic fractures. This suggests that characteristics of the cranial fracture patterns may be used to differentiate energy level from impact interface in pediatric forensic cases.

This research examines the utility of patella outline shape for matching 3D scans of patellae to knee radiographs using elliptical Fourier analysis and subjective methods of human visual comparison of patellae across radiographs for identification purposes. Repeat radiographs were captured of cadaver's knees for visual comparison before patellae were extracted and skeletonized for quantitative comparisons. Quantitative methods provided significant narrowing down of the candidate pool to just a few potential matches (<5% of original sample), while the human analysts showed high capacity for correctly matching radiographs, irrespective of educational level (positive predictive value = 99.8%). The successful computerized matching based on a single quantified patella trait (outline shape) helps explain the potency achieved by subjective visual examination. This work adds to a growing body of studies demonstrating the value of single isolated infracranial bones for human identification via radiographic comparison.

The purpose of this presentation is to report on the preliminary analyses of skeletal remains recovered from an extended-use Roman workshop complex at the site of Spolverino, located near modern-day Alberese, Italy. The site was excavated in 2010-2013 by the Soprintendenza per i Beni Archeologici della Toscana and the University of Sheffield’s Alberese Archaeological Field School as part of a regional investigation into Roman era economic and settlement trends. Located strategically at the mouth of the Ombrone River at the intersection of multiple trade routes, the workshops manufactured glass, metal, and bone goods over four centuries of continuous use. Following the abandonment of the complex in the late 5th century, it was repurposed as a small necropolis prior to its conversion to agricultural fields. Four single-inhumation tombs were found in three rooms and were of three different types.
Osteological analyses included those for demographic information and paleopathological conditions. Analysis revealed the presence of two subadults and two adult males. All individuals expressed indicators of active stress, including moderate cribra orbitalia in the subadults and active periosteal reactions in the adults. Of note was one male who expressed evidence of rhinomaxillary syndrome in conjunction with other pathologies.
The burial of these individuals at Spolverino represents a key phase of transition in the transformation of the landscape from thriving manufacturing district to agricultural fields that persist today. Spolverino’s abandonment and conversion into a necropolis provide insight into the collapse of the Late Antique settlement network along the Ombrone.

The goal of this presentation is to inform attendees about research on the influence of impact interface on fracture patterns in controlled head drop experiments onto the parietal bone with a subadult porcine (Sus scrofa) model.

This presentation will impact the forensic community by comparing controlled head drops onto rigid and compliant interfaces.
In forensic investigations, distinguishing accidental from inflicted injury based on skull fracture alone is challenging as both cases may produce similar patterns. From this, our research team identified the need for a deeper understanding of the fracture mechanics of the skull through controlled simulation of traumatic head injuries.

Our recent studies have demonstrated the utility of an infant porcine model in simulating impacts to the developing human skull. We have shown that increasing the impact energy applied to entrapped heads increases the number and length of cranial fractures (1, 2). The current study examines the effect of interface compliance on skull fractures from head drops in the porcine model.

The hypotheses of this study were twofold: first, that head drops onto a rigid interface would produce more fracturing than drops onto a compliant interface; secondly, that fracture patterns produced in high-energy head drops onto a compliant interface would be similar to those produced by lower-energy drops onto a rigid interface.

In order to generate a single impact onto the center of the right parietal bone, a custom drop tower was developed with an adjustable height. Specimen heads of a given age could be dropped with a consistent orientation onto various surfaces at the same impact energy. Pigs that had died of natural causes between 3 and 19 days of age (n=87) were collected and frozen within 12 hours of death for this study.

The study was performed with controlled head drops onto a rigid surface and two carpeted interfaces. The rigid surface was a half-inch thick aluminum disk (n=32). “Carpet 1” interface covered the rigid surface with a thin, commercial-grade carpet (n=23), and “carpet 2” interface covered the surface with a thick polyester carpet with an underlayment (n=32).

After impact, the crania were inspected for diastatic fractures, the soft tissue was removed, and the dry cranial bones were reassembled. Fractures were recorded on a standard diagram and the location and length of each was recorded to the nearest millimeter.

Total fracture length from head drops onto the rigid surface was significantly higher than both carpet 1 (p=0.002) and carpet 2 (p<0.001). Carpet 1 also produced a significantly higher total fracture length than carpet 2 (p=0.009).

Carpet 2 data was compared to previously published low-energy drops onto a rigid interface (1). Total fracture length (p=.259) and total number of fractures (p=.204) showed no significant difference. However, low-energy rigid drops produced significantly more diastatic fractures (p<.001) and fractures that crossed through a suture (p=.049). The low-energy rigid drop tests also tended to produce more fractures in bones other than the impacted bone (p=.057).

In summary, this study showed that a head dropped onto a rigid interface would produce significantly more total fracturing than one dropped onto a compliant interface. Energy absorbed through deformation of the compliant interface reduces the impact energy imparted to the skull to lessen cranial fracturing.

Furthermore, while the degree of fracturing was similar for high-energy drops onto a compliant interface as low-energy drops onto a rigid interface, the fracture patterns were different, so that these impact scenarios would be distinguishable post-trauma.

These results demonstrate that impact interface may be a significant factor in the interpretation of injury causation that involves cranial fractures in the pediatric trauma victim.

This project was supported by the National Institute of Justice, Office of Justice Programs, United States Department of Justice. The opinions, findings, and conclusions or recommendations expressed in this presentation are those of the authors and do not necessarily reflect the views of the Department of Justice.

References:

1. Baumer TG, Passalacqua NV, Powell BJ, Newberry WN, Fenton TW, Haut RC. Age-dependent fracture characteristics of rigid and compliant surface impacts on the infant skull - a porcine model. J Forensic Sci 2010;55(4):993-997.

2. Powell BJ, Passalacqua NV, Baumer TG, Fenton TW, Haut RC. Fracture patterns on the infant porcine skull following severe blunt impact. J Forensic Sci 2012;57(2):312-317.