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Abstract
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.
- ORAL & MAXILLOFACIAL SURGERY
- FORENSIC MEDICINE
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Key messages
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Protecting the neck from explosively propelled fragments has traditionally been achieved through a collar attached to the ballistic vest.
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An Enhanced Protection Under Body Armour Combat Shirt (EP-UBACS) collar has been identified as an additional method of providing neck protection.
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Computerised surface wound mapping would suggest that reinforcing the neck collar of an EP-UBACS would reduce injury severity from neck wounds.
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This technique may not be applicable for assessing body armour coverage to other parts of the body.
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We would recommend development of models that incorporate the underlying anatomical structures and not just the skin surface.
Introduction
Combat neck injury continues to be a significant source of mortality and long-term morbidity experienced by UK service personnel deployed to Afghanistan.1 Protection against such wounds is currently in the form of a half (Figure 1A) or full detachable neck collar that secures to the OSPREY body armour vest. This collar comes in two heights, both of which are rarely worn due to poor integration with the other protective equipment as well as being uncomfortable.1 Therefore, when no collar is worn, the neck is potentially vulnerable and is not protected from the threats on the battlefield (Figure 1B). Even when the neck collar is worn, there is also a potential gap in ballistic protective material between it and the OSPREY vest anteriorly (Figure 1A) and posteriorly.
The current UK Mark IV OSPREY ballistic vest worn on an anatomical manikin with half neck collar (A) and without (B). A potential gap in the ballistic protective material between neck collar and vest can seen anteriorly (arrow).
The Under Body Armour Combat Shirt (UBACS) (Figure 2) is routinely worn under OSPREY body armour. This garment is designed for comfort (it has no buttons or pockets on the chest, unlike the combat shirt) and for sweat and heat dissipation. As the UBACS is a clothing item, it does not contain any ballistic protection per se, but does cover the lower neck when zipped up. Due to the vulnerability of the neck when a protective collar is not worn, it was considered a ‘quick-win’ to reinforce the neck collar of a UBACS collar with ballistic protective material, a design termed the Enhanced Protection UBACS (EP-UBACS). This concept of protection would be similar to the tiered Pelvic Protection system, where a reinforced UBACS collar could theoretically provide the minimum amount of protection (eg, Tier 1 level protection) with the option to increase the level of protection by wearing an OSPREY neck collar (Tier 2 level protection) in situations of increased threat.2 An ergonomics trial of the EP-UBACS system was undertaken recently and demonstrated its potential acceptability by soldiers.3 However, limited medical information was available to demonstrate its potential effectiveness and therefore justify the cost of its procurement.
The current Under Body Armour Combat Shirt issued to UK service personnel deploying to Afghanistan. Its collar does not provide any ballistic protection to the neck.
Surface wound mapping (SWM) is the process by which the wound locations of projectiles perforating the skin are graphically recorded.1 ,4 ,5 SWM has been attempted intermittently since World War I,6–8 but has never gained mainstream acceptance6 despite the potential for validation in coverage provided by differing designs of Personal Protective Equipment (PPE). The Defence Science and Technology Laboratory in conjunction with the Royal Centre for Defence Medicine (RCDM) has developed a novel electronic SWM tool called the Interactive Mapping Analysis Platform (IMAP),6 designed to be used prospectively, collecting information as close to the point of wounding as possible. The neck portion of the body model within IMAP uses the skin geometries of the Zygote V.5.0 (Zygote Media Group Inc, American Fork, Utah, USA), a commercially procured model that uses geometries based from MRI and CT scans of humans. This model has in turn been scaled to be anthropometrically accurate for a 50th percentile UK male service person. The tool allows the coverage of any type of PPE to be imported, scaled and superimposed onto the skin surface.6
Information on the types of injuries sustained by UK service personnel is contained in the UK Joint Theatre Trauma Registry (JTTR) held by RCDM.1 ,6 Information is entered retrospectively using clinical records for survivors and post-mortem records for fatalities.1 ,7 For epidemiological purposes, each individual injury is also ascribed an Abbreviated Injury Scale (AIS) score, ranging from 1 (minor) to 6 (maximal, currently untreatable). These are excellent predictors of injuries causing immediate or early threat to life.5 By using AIS scores, and by linking IMAP and the JTTR, it is theoretically possible to relate the location of each surface wound sustained by a service person to a clinical outcome. This could potentially provide powerful validation of the coverage required for types of body armour. The aim of this study was therefore to use the IMAP tool to objectively compare the coverage and potential reduction in predicted injury severity provided by three novel designs of EP-UBACS neck collar to provide evidence for its potential procurement for use by UK forces deployed to Afghanistan.
Methods
Three Tier 1 EP-UBACS prototypes (A–C) were developed, reflecting potential design features for consideration in an integrated collar. Prototype A was identical to an existing UBACS (Figure 3), with the only modification being the incorporation of ballistic protective material into the collar. Such modifications to existing garments have recently been suggested as simple methods of providing protection against explosive fragmentation without resulting in an additional physiological burden.9 Prototypes B and C (Figure 3) replaced the standard UBACS zipped collar with a crossover design, thus enabling the collar to stand up without the requirement for a zip. Prototypes B and C were identical in shape and size, but in Prototype B, the ballistic material was bonded to provide rigidity and greater standoff from the surface of the neck. Prototype C had identical standoff from the neck as Prototype A, both of which were less than Prototype B. 3D computer aided design (CAD) scans of the EP-UBACS prototypes were generated. The resultant images were imported into the IMAP tool, with only the ballistic protective components of the collars displayed.
Three Enhanced Protection Under Body Armour Combat Shirt prototypes worn on an anatomical manikin: reinforced standard collar (Prototype A), crossover collar with increased standoff from skin (Prototype B) and crossover collar with reduced standoff from skin (Prototype C).
The JTTR was used to identify all UK service personnel deployed to Afghanistan (survivors, killed in action and died of wounds) who sustained a combat induced penetrating neck injury between 01 January 2010 and 31 December 2011. All wounds caused by explosively propelled fragments were charted pictorially and for the purpose of this study blunt wounds and those due to gunshot wounds were excluded. Wound locations for those evacuated to the UK were prospectively gathered directly from examining the patient, either on the ward or in the Intensive Care Unit at the Queen Elizabeth Hospital, Birmingham. Wound locations for those soldiers who were killed were derived retrospectively using photographs contained in the post-mortem records in conjunction with the Home Office pathologists who originally undertook the post-mortem examination. Where possible, it was determined whether the service person was wearing an OSPREY neck collar and UBACS shirt at the time of injury. Wound location data were imported into the IMAP tool by the same clinician who had determined the wound locations. When the CAD scans of the collars were placed on the neck of the IMAP model, the potential reduction in wound entry incidence and subsequent outcome provided by each collar could be determined (Figure 4). The coverage provided by each collar was compared for three potential shot lines: (a) anterior horizontal, (b) lateral horizontal and (c) anterior ground (measured at 45° inferiorly to the horizontal).
Entry wound locations visualised from anterior horizontal (row 1), lateral horizontal (row 2) and anterior ground (row 3). A standard Under Body Armour Combat Shirt (UBACS) with no integral neck protection (U) and Enhanced Protection UBACS Prototypes A–C are shown.
AIS scores were used to compare the effect on injury severity provided by the differing coverage of the three EP-UBACS prototypes. The AIS scores for each neck wound not covered by a prototype collar were tabulated (Table 1) and any neck wound entry location covered by an EP-UBACS collar was discarded (as it was assumed that the collar defeated the projectile). AIS scores were compared between prototypes for anterior horizontal and anterior ground shot lines.
Distribution of the actual and predicted neck wound AIS scores for horizontal and ground-based threats
Results
Between 1 January 2010 and 31 December 2011, neck wounds caused by explosively propelled fragments were present in 81/871 (9%) of injured UK service personnel deployed on operations in Afghanistan. Of these 81 neck wounds, 74 were penetrating (and therefore mapped) and the remaining seven were blunt and excluded from further analysis. No casualties sustaining neck injuries were wearing an OSPREY collar at the time of injury but all 74 were wearing a standard UBACS.
The entry wound locations of all 74 service personnel injured by penetrating explosively propelled fragments is pictorially represented in Figure 4. The AIS scores for these wounds are provided in Table 1. The second column shows the AIS scores derived from all known wound locations and represent the effect of not wearing neck protection, as all service personnel were wearing an unmodified UBACS and no OSPREY neck collar.
The reduction in the incidence of wound entry locations in a horizontal shot line was greater for the crossover collars (Prototypes B + C) than the reinforced standard collar (Prototype A). The crossover collar with the greater standoff from the skin (Prototype B) provided the greatest reduction in wound incidence from ground-based threats. The most marked reduction was seen in AIS 5 scores, primarily due to coverage of those AIS scores pertaining to common carotid artery damage with all EP-UBACS designs.
When a standard UBACS collar was reinforced with ballistic material alone (Prototype A), a potential gap was observed beneath the collar and the top of the OSPREY vest. Wounds in this location were associated with high AIS scores (4 or 5). A potential gap was also observed in the midline of the collar representing the zip which provides no ballistic protection.
Discussion
The aim of this project was to determine whether computerised wound mapping using the IMAP tool could objectively compare the medical effectiveness of EP-UBACS neck collars. Overlaying the neck collars onto the entry wound locations demonstrated that all of the designs could potentially prevent a large proportion of the resultant wounds as coded by AIS scores. The marked reductions in AIS 5 scores in particular by all prototype designs would be expected to reduce mortality, as it is the injuries represented by the codes with AIS scores of 5 that have previously been demonstrated to be responsible for potentially preventable deaths.1 Those wounds at the base of the neck (Zone 1), particularly anteriorly, had a large number of AIS 5 scores and an additional semi-circle of ballistic material underneath the EP-UBACS collar could potentially prevent penetration of fragments passing into the gap between the OSPREY ballistic neck collar and vest (Figure 5).
Suggested modifications to the existing Under Body Armour Combat Shirt (UBACS) based on this study: (A) Current UBACS; (B) Incorporation of ballistic protective material within the neck collar (the Enhanced Protection UBACS (EP-UBACS) alone leaves an area between the collar and the OSPREY vest unprotected (highlighted yellow); (C) Further suggested modification to EP-UBACS with additional semicircle of ballistic protective material (arrows) below the collar.
The ability to overlay any armour design onto a standardised human was identified as being potentially the most useful part of this tool. For example, the ability of the model to view the predicted neck coverage from a ground-based threat demonstrated that while the two crossover collars (Prototypes B+C) were equal in size, the one with the greater standoff from the skin (Prototype B) provided a greater reduction in wound incidence and AIS scores from ground-based threats of the two. We would therefore recommend developing this component of the tool as an independent injury model using the underlying anatomical structures and not just the skin surface.
Finally, we do recognise that this approach to injury prediction has a number of limitations. Overlaying body armour designs in this manner must assume that the ballistic protective material was capable of retarding the fragment whereas in reality this approach alone cannot dictate whether the material would be capable as neither the mass or impact velocity of the fragment was known. This approach also relies on accurate knowledge of the entry wound locations for injuries coded by the AIS system. Such wound mapping information has been demonstrated previously to only be accurate if it is obtained prospectively6 and to date has only been collected for the face and neck body regions. Finally, the use of AIS scores alone without verification of outcome by review of clinical hospital records for survivors or post-mortem records for those who died means that this technique should be seen more as a manner of comparing coverage than an injury prediction model.
Conclusions
Computerised wound mapping using IMAP suggests that the reinforced neck collar of an EP-UBACS would be likely to reduce injury severity from combat neck injury. However, without accurate knowledge of entry wound locations for injuries to other body areas as well as this technique using AIS scores without clinical or pathological verification may limit its further use in the future. Consideration should be made towards developing future EP-UBACS prototypes that provide greater stand-off from the skin than the current UBACS collar as they provide greater neck skin coverage for ground-based threats. An additional semi-circle of ballistic material underneath the EP-UBACS collar could potentially prevent penetration of fragments passing into the gap between the OSPREY ballistic neck collar and vest. 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 as an independent injury model using the underlying anatomical structures and not just the skin surface.
Acknowledgments
Permission to publish has kindly been granted by Her Majesty's Coroners for Wiltshire and Swindon, and Oxfordshire with jurisdiction for investigating the deaths of service personnel. This paper was also published with the permission of Joint Medical Command and the Defence Science and Technology Laboratory on behalf of the Controller of HMSO.
Footnotes
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Contributors Planning: JB, LAB. Conduct: JB, LAB, NC, RD. Reporting: JB, LAB, NC, RD, AH, EL.
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Competing interests None.
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Ethics approval This research was approved by the Defence Medical Services Research and Ethics committee and all patient data have been anonymised.
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Provenance and peer review Not commissioned; externally peer reviewed.