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 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.

Axe injury pattern in homicide

Chop or slash wounds are produced by sharp-edged tools such as an axe, or a machete. This paper presents a case of a violent death of a 57 year-old-man. Autopsy revealed deformation of the right side of the head. A total of 23 slash, stab and cut wounds as well as contused lacerations were identified on the scalp as well as the face and the neck. In addition, superficial abrasions and bruises were identified on the skin. The immediate cause of death was due to extensive brain contusion following fragmentation of the neurocranium. The injuries resulting in the death of the victim were sustained during an assault on the head with an axe, which was used both as a slashing tool and a blunt instrument.

Weekend woodsmen: Overview and comparison of injury patterns associated with power saw and axe utilization in the United States

INTRODUCTION

Power saw and axe injuries are associated with significant morbidity and are increasingly managed in the emergency department (ED). However, these injuries have not been summarily reported in the literature. We aim to evaluate and compare the common injury patterns seen with use of power saws and axes.

MATERIALS AND METHODS

Data from the National Electronic Injury Surveillance System- All Injury Program (NEISS-AIP) database was analyzed during 2006 to 2016. All patients with nonfatal injuries relating to the use of power saws or axes were included. Baseline demographics type and location of injuries were collected. Descriptive statistical analyses were performed using Chi Square or Fisher's exact test.

RESULTS

Information on (n = 18,250) patients was retrieved from the NEISS-AIP database. Injuries were caused by power saw n = 16,384 (89%) and axe n = 1866 (11%) use, and mostly involved males (95%). The most frequently encountered injury was laceration axe n = 1166 (62.5%); power saw n = 11,298 (68.9%). Approximately half of all injuries in both groups involved the fingers and hand. Most injuries occurred at home (65%) and were attributed to power saw use (89%).

CONCLUSIONS

Power saws and axes can cause significant injuries, the majority of which occurred at home and were primarily associated with power saw use. Lacerations and injuries to the finger and hand were prevalent in both study groups. Further research into power saw and axe injuries should place emphasis on preventative measures and personal protective equipment (PPE).

LEVEL OF EVIDENCE

IV Study type: Retrospective review.