Blast-related fracture patterns: a forensic biomechanical approach

Abstract

Improved protective measures and medical care has increased the survivability from battlefield injuries. In an attempt to reduce the debilitating consequences of blast injury, understanding and mitigating the effects of explosion on the extremities is key. In this study, forensic biomechanical analyses have been applied to determine mechanisms of injury after the traumatic event. The aims of this study were (i) to determine which effects of the explosion are responsible for combat casualty extremity bone injury in two distinct environments, namely open, free-field (open group), and in vehicle or in cover (enclosed group), and (ii) to determine whether patterns of combat casualty bone injury differed between environments. Medical records of casualties admitted to a military hospital in Afghanistan were reviewed over a six-month period. Explosive injuries have been sub-divided traditionally into primary, secondary and tertiary effects. All radiographs were independently reviewed by a military radiologist, a team of military orthopaedic surgeons and a team of academic biomechanists, in order to determine 'zones of injury' (ZoIs), and their related mechanisms. Sixty-two combat casualties with 115 ZoIs were identified. Thirty-four casualties in the open group sustained 56 ZoIs; 28 casualties in the enclosed group sustained 59 ZoIs. There was no statistical difference in mean ZoIs per casualty between groups ( p ¼ 0.54). There was a higher proportion of lower limb injuries in the enclosed group compared with the open group ( p , 0.05). Of the casualties in the open group, 1 ZoI was owing to the primary effects of blast, 10 owing to a combination of primary and secondary blast effects, 23 owing to secondary blast effects and 24 owing to tertiary blast effects. In contrast, tertiary blast effects predominated in the enclosed group, accounting for 96 per cent of ZoIs. These data clearly demonstrate two distinct injury groups based upon the casualties' environment. The enclosed environment appears to attenuate the primary and secondary effects of the explosion. However, tertiary blast effects were the predominant mechanism of injury, with severe axial loading to the lower extremity being a characteristic of the fractures seen. The development of future mitigation strategies must focus on reducing all explosion-related injury mechanisms. Integral to this process is an urgent requirement to better understand the behaviour of bone in this unique environment.

Characteristics and mechanisms of extremity injuries caused by mine blasts in shoals

“…In 1-2 ms post-detonation, the detonation products and environmental fragments contact the limb, causing destruction of the traumatized soft tissue. [7,8] When a mine blast occurs on land, the air surrounding the explosion is compressed and absorbs energy from the explosion. Moreover, the blast wave displaces immediately the surrounding air and generates high velocity air flow that can cause injury.…”

Prospects for studying how high-intensity compression waves cause damage in human blast injuries

“…Specifically, in an anti-vehicle mine explosion, such as those seen in recent and current theatres of operation, the occupants sustain severe injuries in their lower limbs and particularly in the foot and ankle complex [5]. Simulation of such an event in vitro and in silico could elucidate the injury mechanisms and allow for the development of appropriate mitigation.…”

“…Ramasamy, et al [5] have recently published a systematic comparison (see Table 1) of the zones of skeletal injury for blast victims, clearly indicating a bias to lower limb injuries arising from IED blasts experienced in enclosed surrounding (e.g. within a vehicle).…”

“…In the intervening years, the anatomical pattern of wounding has remained constant with over 70% of combat wounds being inflicted on the extremities [3][4][5]. Improvements in body armour design, enhanced pre-hospital care, and rapid aeromedical evacuation have led to a significant decrease in the number of fatalities in modern conflicts [5]; indeed there was an increase in survivability from 69.7% during WWII to 88.6% in most recent conflict in Iraq [6]. This increase in survivability has been accompanied by an increase in casualties with multiple and complex injuries, associated in particular with the use of Improvised Explosive Devices (IED).…”

Composite nature of fresh skin revealed during compression

“…In blast exposure, pressure pulses and strain rate deformation of hard and soft tissues result in injuries and tissue dysfunction uncommon away from the battlefield. 4 Key contributors to the generation of blast injury include the overpressure of the blast wave in conjunction with its duration (impulse), the environment in which the explosion occurs (free field versus confined space), and the proximity of the target to the explosion. 5 The levels of force and acceleration experienced in blast injury can be considerable.…”