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Fracture energy threshold in parry injuries due to sharp and blunt force


Gentile, Simon; Kneubuehl, Beat P; Barrera, Vera; Dobay, Akos; Thali, Michael J; Bolliger, Stephan A (2019). Fracture energy threshold in parry injuries due to sharp and blunt force. International journal of legal medicine, 133(5):1429-1435.

Abstract

Blows with axes, machetes or blunt objects such as baseball bats, truncheons, etc. are often parried, resulting in typical parry injuries, or so-called nightstick fractures to the ulna. In this study, we sought to assess the impact energy required to break the ulna in such parry incidents in an experimental setting using semisynthetic and fully synthetic models. Twenty-seven sheep radii and 33 polyurethane synthetic bones were cast into gelatin prior to being fired at with missiles made of a section of an axe blade or steel rod at different firing velocities using a compressed-nitrogen cannon. Each model was then examined as to the presence of hair-line fractures or complete fractures. Sheep bones and synthetic bones displayed comparable results when struck by the axe missile; here, a clear fracture threshold was evident between 14.00 and 15.26 J. When struck by the rod missile, only the synthetic bones produced significant results, namely a fracture threshold between 20.15 and 23.59 J. In conclusion, our results show an ulnar fracture threshold of approximately 15 J when struck by an axe. The experiments regarding blows with a rod displayed a fracture threshold of around 22 J, but, as this could not be validated with biological bones, this result is questionable.

Abstract

Blows with axes, machetes or blunt objects such as baseball bats, truncheons, etc. are often parried, resulting in typical parry injuries, or so-called nightstick fractures to the ulna. In this study, we sought to assess the impact energy required to break the ulna in such parry incidents in an experimental setting using semisynthetic and fully synthetic models. Twenty-seven sheep radii and 33 polyurethane synthetic bones were cast into gelatin prior to being fired at with missiles made of a section of an axe blade or steel rod at different firing velocities using a compressed-nitrogen cannon. Each model was then examined as to the presence of hair-line fractures or complete fractures. Sheep bones and synthetic bones displayed comparable results when struck by the axe missile; here, a clear fracture threshold was evident between 14.00 and 15.26 J. When struck by the rod missile, only the synthetic bones produced significant results, namely a fracture threshold between 20.15 and 23.59 J. In conclusion, our results show an ulnar fracture threshold of approximately 15 J when struck by an axe. The experiments regarding blows with a rod displayed a fracture threshold of around 22 J, but, as this could not be validated with biological bones, this result is questionable.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Legal Medicine
Dewey Decimal Classification:340 Law
610 Medicine & health
Scopus Subject Areas:Health Sciences > Pathology and Forensic Medicine
Uncontrolled Keywords:Pathology and Forensic Medicine
Language:English
Date:1 September 2019
Deposited On:16 Dec 2019 11:11
Last Modified:15 Apr 2020 23:46
Publisher:Springer
ISSN:0937-9827
OA Status:Closed
Publisher DOI:https://doi.org/10.1007/s00414-019-02022-3
PubMed ID:30788564

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