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

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 expe...

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Bibliographic Details
Published in:International journal of legal medicine 2019-09, Vol.133 (5), p.1429-1435
Main Authors: Gentile, S., Kneubuehl, B. P., Barrera, V., Dobay, A., Thali, M. J., Bolliger, S. A.
Format: Article
Language:English
Subjects:
Animals
Biological effects
Bone Substitutes
Bones
Forensic Medicine
Fractures
Gelatin
Injuries
Kinetics
Medical Law
Medicine & Public Health
Missiles
Models, Animal
Original Article
Polyurethane resins
Polyurethanes
Radius Fractures - classification
Sheep
Ulna
Ulna Fractures - classification
Weapons - classification
Wounds, Nonpenetrating
Wounds, Penetrating
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Summary: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.
ISSN:0937-9827
1437-1596
DOI:10.1007/s00414-019-02022-3