Introduction The influence of rib impact on thoracic gunshot trauma remains unclear, despite its high occurrence. This study therefore investigates the effect of rib impact on a bullet’s terminal properties and injury severity.
Methods Two bullets were used: 5.56×45 mm (full charge and reduced charge) and 7.62×51 mm (full charge). For each bullet, three impact groups were tested: (1) plain 10% ballistic gelatin (control) conditioned at 4°C, (2) intercostal impact, and (3) rib impact, the latter two tested with samples of porcine thoracic walls embedded in gelatin. Analysis included penetration depth, trajectory change, yaw, fragmentation, velocity reduction, energy deposition and temporary and permanent cavity characteristics.
Results No significant differences were observed for most variables. Differences were found between rib (and intercostal) impact and the control groups, suggesting that the inclusion of thoracic walls produces an effect more significant than the anatomical impact site. Effects were ammunition specific. For the 7.62×51 mm round, rib impact caused an earlier onset of yaw and more superficial permanent gelatin damage compared with plain gelatin. This round also formed a larger temporary cavity on rib impact than intercostal impact. Rib (and intercostal impact) created a smaller temporary cavity than the control for the 5.56×45 mm round. For the reduced-charge 5.56×45 mm round, rib and intercostal impact produced greater velocity reduction compared with plain gelatin.
Conclusions This study provides new insights into the role of rib impact in thoracic gunshot injuries, and indicates that the effects are ammunition dependent. Unlike the 5.56×45 mm rounds, rib impact with the 7.62×51 mm rounds increases the risk of severe wounding.
- rib impact
- intercostal muscle impact
- terminal ballistics
- thoracic gunshot trauma
- wound severity
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Contributors All authors contributed to this work in some way, be it experimental design, data collection and analysis, or manuscript editing. DCK is the corresponding author.
Funding The project was funded by the New Zealand Defence Force.
Competing interests None declared.
Patient consent Not required.
Ethics approval Ethical approval was sought but deemed unnecessary by the University of Auckland Animal Ethics Committee because all tissues were obtained after production for the human food chain.
Provenance and peer review Not commissioned; externally peer reviewed.
Presented at Poster and paper presentation at the 30th International Ballistic Society Symposium, California, September 2017; Oral presentation at ANZFSS 23rd Symposium on Forensic Sciences, Auckland, September 2016.
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