Defining the essential anatomical coverage provided by military body armour against high energy projectiles.

INTRODUCTION: Body armour is a type of equipment worn by military personnel that aims to prevent or reduce the damage caused by ballistic projectiles to structures within the thorax and abdomen. Such injuries remain the leading cause of potentially survivable deaths on the modern battlefield. Recent developments in computer modelling in conjunction with a programme to procure the next generation of UK military body armour has provided the impetus to re-evaluate the optimal anatomical coverage provided by military body armour against high energy projectiles. METHODS: A systematic review of the literature was undertaken to identify those anatomical structures within the thorax and abdomen that if damaged were highly likely to result in death or significant long-term morbidity. These structures were superimposed upon two designs of ceramic plate used within representative body armour systems using a computerised representation of human anatomy. RESULTS AND CONCLUSIONS: Those structures requiring essential medical coverage by a plate were demonstrated to be the heart, great vessels, liver and spleen. For the 50th centile male anthropometric model used in this study, the front and rear plates from the Enhanced Combat Body Armour system only provide limited coverage, but do fulfil their original requirement. The plates from the current Mark 4a OSPREY system cover all of the structures identified in this study as requiring coverage except for the abdominal sections of the aorta and inferior vena cava. Further work on sizing of plates is recommended due to its potential to optimise essential medical coverage.

Using computerised surface wound mapping to compare the potential medical effectiveness of Enhanced Protection Under Body Armour Combat Shirt collar designs.

INTRODUCTION: Protecting the neck from explosively propelled fragments has traditionally been achieved through a collar attached to the ballistic vest. An Enhanced Protection Under Body Armour Combat Shirt (EP-UBACS) collar has been identified as an additional method of providing neck protection but limited evidence as to its potential medical effectiveness exists to justify its procurement. METHOD: Entry wound locations and resultant medical outcomes were determined using Abbreviated Injury Scale (AIS) for all fragmentation neck wounds sustained by UK soldiers between 01 January 2010 and 31 December 2011. Data were prospectively entered into a novel computerised tool base and comparisons made between three EP-UBACS neck collar designs in terms of predicted reduction in AIS scores. RESULTS: All collars reduced AIS scores, with the greatest reduction provided by designs incorporating increased standoff from the neck and an additional semi-circle of ballistic material underneath the collar at the front and back. DISCUSSION: This technique confirms that reinforcing the neck collar of an EP-UBACS would be expected to reduce injury severity from neck wounds. However, without knowledge of entry wound locations for injuries to other body areas as well as the use of AIS scores without clinical or pathological verification its further use in the future may be limited. The ability to overlay any armour design onto a standardised human was potentially the most useful part of this tool and we would recommend developing this technique using underlying anatomical structures and not just the skin surface.

Demonstrating the effectiveness of body armour: a pilot prospective computerised surface wound mapping trial performed at the Role 3 hospital in Afghanistan.

INTRODUCTION: Modern body armour clearly reduces injury incidence and severity, but evidence to actually objectively demonstrate this effect is scarce. Although the Joint Theatre Trauma Registry (JTTR) alone cannot relate injury pattern to body armour coverage, the addition of computerised Surface Wound Mapping (SWM) may enable this utility. METHOD: Surface wound locations of all UK and NATO coalition soldiers, Afghan National Army and Police and local nationals injured by explosively propelled fragments and treated in the Role 3 UK-led Field Hospital in Camp Bastion, Afghanistan, between 8 July and 20 October 2012 were prospectively recorded. The Abbreviated Injury Scores (AIS) and relative risk of casualties sustaining injuries under a type of body armour were compared with those that did not wear that armour. RESULTS: Casualties wearing a combat helmet were 2.7 times less likely to sustain a fragmentation wound to the head than those that were unprotected (mean AIS of 2.9 compared with 4.1). Casualties wearing a body armour vest were 4.1 times less likely to sustain a fragmentation wound to the chest or abdomen than those that were unprotected (mean AIS of 2.9 compared with 3.9). Casualties wearing pelvic protection were 10 times less likely to sustain a fragmentation wound to the pelvis compared with those that were unprotected (mean AIS of 3.4 compared with 3.9). DISCUSSION: Computerised SWM has objectively demonstrated the ability of body armour worn on current operations in Afghanistan to reduce wound incidence and severity. We recognise this technique is limited in that it only records the surface wound location and may be specific to this conflict. However, gathering electronic SWM at the same time as recording injuries for the JTTR was simple, required little extra time and therefore we would recommend its collection during future conflicts.

Novel method for comparing coverage by future methods of ballistic facial protection.

The wearing of eye protection by United Kingdom soldiers in Afghanistan has reduced the morbidity caused by explosive fragments. However, the remaining face remains uncovered because there is a lack of evidence to substantiate the procurement of methods to protect it. Using a new computerised tool we entered details of the entry sites of surface wounds caused by explosive fragments in all UK soldiers who were injured in the face between 1 January 2010 and 31 December 2011. We compared clinical and predicted immediate and long term outcomes (as defined by the Abbreviated Injury Score (AIS) and the Functional Capacity Index (pFCI), respectively). We also used the tool to predict how additional protection in the form of a visor and mandible guard would affect outcomes. A soldier wearing eye protection was 9 times (1.03/0.12) less likely to sustain an eye injury than one without. However, 38% of soldiers in this series were not wearing eye protection at the time of injury. There was no significant difference between the AIS and pFCI scores predicted by the tool and those found clinically. There is limited evidence to support the use of a mandible guard; its greatest asset is better protection of the nose, but a visor would be expected to reduce long-term morbidity more than eye protection alone, and we recommend future trials to assess its acceptability to users. We think that use of this novel tool can help in the selection of future methods of ballistic facial protection.

Determining the wounding effects of ballistic projectiles to inform future injury models: a systematic review.

INTRODUCTION: Penetrating wounds from explosively propelled fragments and bullets are the most common causes of combat injury experienced by UK service personnel on current operations. There is a requirement for injury models capable of simulating such a threat in order to optimise body armour design. METHOD: A systematic review of the open literature was undertaken using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology. Original papers describing the injurious effects of projectiles on skin, bone, muscle, large vessels and nerves were identified. RESULTS: Projectiles injure these tissues by producing a permanent wound tract (PWT), comprised of a central permanent wound cavity, in conjunction with a zone of irreversible macroscopic tissue damage laterally. The primary mechanism of injury was the crushing and cutting effect of the presented surface of the projectile, with an additional smaller component due to macroscopic damage produced by the radial tissue displacement from the temporary tissue cavity (TTC). No conclusive evidence could be found for permanent pathological effects produced by the pressure wave or that any microscopic tissue changes due to the TTC (in the absence of visible macroscopic damage) led to permanent injury. DISCUSSION: Injury models should use the PWT to delineate the area of damage to tissues from penetrating ballistic projectiles. The PWT, or its individual components, will require quantification in terms of the amount of damage produced by different projectiles penetrating these tissues. There is a lack of information qualifying the injurious effect of the temporary cavity, particularly in relation to that caused by explosive fragments, and future models should introduce modularity to potentially enable incorporation of these mechanisms at a later date were they found to be significant.

Perforation of fragment simulating projectiles into goat skin and muscle.

INTRODUCTION: Ballistic gelatin is the most common tissue simulant used to reproduce the penetration of projectiles into muscle but published data to support its use are primarily based on bullets, despite explosive fragments being the most common cause of injury to soldiers on current operational deployments. Published ballistic tests using animal and artificial skin and muscle tissue surrogates also lack standardisation in methodology such that limited comparisons with that of human tissues can currently be made. METHOD: Three masses of cylindrical NATO standardised fragment simulating projectiles (FSPs) were fired at 20% ballistic gelatin and the hind thighs of a killed goat. Threshold (V(th)) and V(50) velocities required for skin perforation and depth of penetration (DoP) into muscle were compared with gelatin. The intercept and gradient of the linear regression lines for DoP versus velocity were compared between gelatin and goat with significance defined as p<0.05. RESULTS: V(50) goat skin perforation velocities for the 0.16, 0.49 and 1.10 g FSPs were 121.1, 103.7 and 97.8 m/s, respectively. There was a significant difference in the V(50) required to perforate the gelatin surface compared with goat skin for the 0.16 and 0.49 g FSPs but not the 1.10 g. There was no statistical difference in the gradients for DoP versus velocity between animal and gelatin for either the 0.16 or 1.10 g FSPs. DISCUSSION: This study has produced data for skin perforation velocities and generated algorithms describing velocity versus predicted DoP into muscle for three standardised projectiles, which will be used to improve the fidelity of future injury models. 20% gelatin was demonstrated to accurately reproduce the retardation of the 1.10 g FSPs into goat muscle but the addition of a skin simulant will be required to accurately predict DoP for FSPs less than 1.10 g.

The development and introduction of ballistic protection of the external genitalia and perineum.

In response to an Urgent Operational Requirement, the UK Ministry of Defence (MoD) investigated, designed, developed, trialled and subsequently fielded a Tiered Pelvic Protection System to service personnel deployed on Operation HERRICK in Afghanistan. An Urgent Statement of User Requirement (USUR) was drafted in order to equip service personnel with protection for the groin, perineum, buttocks and upper thigh areas from the effects of buried Improvised Explosive Devices (IEDs). Injuries to the groin and pelvic area from buried IEDs can have severe physiological and psychological impact; therefore the aim of the pelvic protection was to reduce the number and severity of such injuries and to improve the outcome, both in terms of quality of life of the survivors and increase the chances of survival. The aim of this paper is to outline some of the research and development that contributed to the design(s) of the Tiered Pelvic Protection System; describe the components of, and report the medical success of, the Tiered Pelvic Protection System.

Developmental framework to validate future designs of ballistic neck protection.

The number of neck injuries has increased during the war in Afghanistan, and they have become an appreciable source of mortality and long-term morbidity for UK servicemen. A three-dimensional numerical model of the neck is necessary to allow simulation of penetrating injury from explosive fragments so that the design of body armour can be optimal, and a framework is required to validate and describe the individual components of this program. An interdisciplinary consensus group consisting of military maxillofacial surgeons, and biomedical, physical, and material scientists was convened to generate the components of the framework, and as a result it incorporates the following components: analysis of deaths and long-term morbidity, assessment of critical cervical structures for incorporation into the model, characterisation of explosive fragments, evaluation of the material of which the body armour is made, and mapping of the entry sites of fragments. The resulting numerical model will simulate the wound tract produced by fragments of differing masses and velocities, and illustrate the effects of temporary cavities on cervical neurovascular structures. Using this framework, a new shirt to be worn under body armour that incorporates ballistic cervical protection has been developed for use in Afghanistan. New designs of the collar validated by human factors and assessment of coverage are currently being incorporated into early versions of the numerical model. The aim of this paper is to describe this developmental framework and provide an update on the current progress of its individual components.

Surface wound mapping of battlefield occulo-facial injury.

INTRODUCTION: Accurately determining the entry location of penetrating eye and face wounds and relating that to mortality and long-term morbidity is of vital importance in the design of future personal protective equipment. METHOD: Hospital and post mortem records for all UK servicemen sustaining penetrating battle injuries to the face or eye during the period 01 January 2005 to 31 December 2009 were analysed. RESULTS: Face and eye injuries were found in 391/1187 (33%) and 113/1187 (10%) of all battle-injured servicemen respectively. 27% of eye wounds from explosions resulted in blindness and a further 17% in significant permanently reduced visual acuity (<6/12). Those servicemen that chose not to wear Combat Eye Protection (CEP) were 36 times more likely to sustain an eye injury from explosive fragmentation than those that did. However only 36% of servicemen chose to wear CEP. 7 deaths could potentially have been prevented had the serviceman chosen to wear their CEP. The lower third of the face was most commonly injured (60%) followed by the upper third (24%). CEP reduced facial injuries as a whole (bone and soft tissue) by 15% (p<0.01). Potentially changing the existing material used for chinstrap and helmet covers to that with ballistic protection would further reduce this incidence by up to 9%. CONCLUSIONS: Although the lower third of the face remains poorly protected, the incidence of lower facial wounds could be further reduced by the use of ballistic visors by servicemen in exposed positions in vehicles (which represented 16% of facial injuries). Such a visor could potentially have prevented 17 deaths. A rigid attachment to the front of a ballistic helmet would allow either a visor, a high visibility LED lamp or a night vision goggle to clip in and we believe this capability should be investigated through future human factor trials.

Blast mines: physics, injury mechanisms and vehicle protection.

Since World War II, more vehicles have been lost to land mines than all other threats combined. Anti-vehicular (AV) mines are capable of disabling a heavy vehicle, or completely destroying a lighter vehicle. The most common form of AV mine is the blast mine, which uses a large amount of explosive to directly damage the target. In a conventional military setting, landmines are used as a defensive force-multiplier and to restrict the movements of the opposing force. They are relatively cheap to purchase and easy to acquire, hence landmines are also potent weapons in the insurgents' armamentarium. The stand-offnature of its design has allowed insurgents to cause significant injuries to security forces in current conflicts with little personal risk. As a result, AV mines and improvised explosive devices (IEDs) have become the most common cause of death and injury to Coalition and local security forces operating in Iraq and Afghanistan. Detonation of an AV mine causes an explosive, exothermic reaction which results in the formation of a shockwave followed by a rapid expansion of gases. The shockwave is mainly reflected by the soillair interface and fractures the soil cap overthe mine. The detonation products then vent through the voids in the soil, resulting in a hollow inverse cone which consists of the detonation gases surrounded by the soil ejecta. It is the combination of the detonation products and soil ejecta that interact with the target vehicle and cause injury to the vehicle occupants. A number of different strategies are required to mitigate the blast effects of an explosion. Primary blast effects can be reduced by increasing the standoff distance between the seat of the explosion and the crew compartment. Enhancement of armour on the base of the vehicle, as well as improvements in personal protection can prevent penetration of fragments. Mitigating tertiary effects can be achieved by altering the vehicle geometry and structure, increasing vehicle mass, as well as developing new strategies to reduce the transfer of the impulse through the vehicle to the occupants. Protection from thermal injury can be provided by incorporating fire resistant materials into the vehicle and in personal clothing. The challenge for the vehicle designer is the incorporation of these protective measures within an operationally effective platform.