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International Journal of Legal Medicine

, Volume 133, Issue 2, pp 501–519 | Cite as

A novel hypothesis for the formation of conoidal projectile wounds in sandwich bones

  • John M. RickmanEmail author
  • James Shackel
Original Article

Abstract

When perforated by a projectile, sandwich bones typically exhibit wounds with a distinct conoidal morphology that is widely utilised both in wound diagnosis and trajectory determinations. However, the dynamic fracture mechanisms underlying this intriguing wound type have yet to be experimentally verified. The most frequently quoted hypothesis for their formation, plug and spall, is difficult to reconcile with the conoidal morphology exhibited by such wounds. The present article carries out a high-speed videographic and micro-computerised tomographic (μ-CT) analysis of perpendicularly produced projectile wounds induced from 139.15 to 896.84 metres per second (m/s) in pig scapulae. Fundamental data on energy absorption, wound shape and bevel symmetry are presented. Cross-sectional fracture morphology revealed by μ-CT raises the novel hypothesis that tensile stresses induced by the projectile in the outer cortex elicit cone crack formation and that this cone crack then propagates catastrophically through the entire sandwich structure. This process results in the momentary formation of a bioceramic conoid, a conoidal volume of bone consisting of all three sandwich bone layers separated from the parent bone by the internal bevel. Fragmentation of the separated volume leaves the conoidal wound behind as its counterpart. The significance of this hypothesis in terms of differential diagnosis and interpretation of bevel shape is discussed.

Keywords

Skeletal trauma Projectile injuries Forensic anthropology Forensic pathology Fracture Sandwich bones 

Notes

Acknowledgements

We are indebted to Dr. David Wood, Andrew Taylor, David Miller and Alan Peare for their considerable technical input and for operation of the gas guns and projectile housing. We would also like to extend our thanks to Kerrie Smith for the error propagation formula and Dr. Keith Rogers and George Adams for their assistance and advice with micro-computerised tomography.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This study was approved by the ethics committee of Cranfield University.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Cranfield Defence and SecurityCranfield University, Defence Academy of the United KingdomShrivenhamUK

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