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Abstract
Introduction This commissioned review discusses military head injuries caused by non-ballistic impacts, penetrating fragments and bullets (including parts of bullets) and behind helmet blunt trauma (BHBT).
Method A systematic review of the literature was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method. The openly accessible literature was reviewed to investigate military head injuries and their severity.
Results Fifty-four sources were identified that included pertinent openly accessible information relevant to this topic. Limited injury data exist for non-ballistic head injuries for UK forces, although some international data exist for parachutists. The majority of fatal head injuries are due to projectiles penetrating through the face rather than through the area of the head covered by the helmet. Penetrating head injuries are primarily caused by fragments, but helmets are more commonly perforated by high-energy rifle bullets than by fragments. No reports of a BHBT injury have been located in the literature.
Conclusions The description of body segment varies among articles and this makes comparisons among datasets difficult. There is a lack of detail regarding the precise position and severity of injuries, and long-term outcome for casualties. It is demonstrated that wearing military helmets reduces fatalities on and off the battlefield. The risk of BHBT injuries is widely referred to, but evidence of their occurrence is not provided by the authors that describe the risk of BHBT occurring. Further research into the causes and severity of head injuries would be useful for designers of military helmets and other associated personal protective equipment, particularly as advances in materials technology means lighter, thinner and more protective helmets are achievable.
- wound ballistics
- head injuries
- cause of injury
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Key messages
There is a lack of detail in the literature regarding body segment definition, and the precise position and severity of head injuries.
Minimal injury data exist for non-ballistic head injuries for UK forces, although some international data exist for parachutists.
Penetrating head injuries are primarily caused by fragments; however, helmets are more commonly perforated by high velocity rifle bullets than by fragments.
Wearing military helmets reduces fatalities; the majority of fatal head injuries are due to projectiles penetrating the face rather than through a helmeted head.
No reported incidents of behind helmet blunt trauma (BHBT) injury have been located in the openly accessible literature. The risk of BHBT injuries is widely referred to, but evidence of their occurrence is not provided.
Introduction
Fragments originating from traditional munitions such as artillery shells, mortars and mines and improvised explosive devices (IEDs) are the major cause of military casualties in general warfare.1–4 Such injuries include penetrating injuries to the head where the skull is penetrated by a primary or secondary projectile. UK military helmets are primarily designed to provide protection to the brain from fragments, and also provide protection from non-ballistic impacts.5–9 Non-ballistic impact injuries are those commonly referred to as ‘bump’ or ‘blunt’ injuries and are caused by blunt or angular threats with relatively low impact energy. A typical modern military helmet comprises of a woven fabric reinforced composite shell, a non-ballistic impact protective liner, suspension and size adjustment systems, comfort pads and a retention system5 ,10; the Mk7 combat helmet, currently worn by UK military personnel, is a typical example of this. Modern solutions for military helmets offer the possibility of protection from bullets (eg, pistol bullets such as 9 mm Luger; 9×19 full metal jacket and rifle bullets such as 7.62×39) and some nations include protection from such threats as a requirement, however, behind helmet blunt trauma (BHBT) is reportedly a concern for several nations.11–13 BHBT injuries, where the helmet is not perforated, reportedly result from the rapid deformation of helmets caused by ballistic impact—the deformation of the helmet may interact with the head resulting in bone fragments entering the brain.11–13
The aim of this systematic review of the open literature was to consider military head injuries caused by non-ballistic impacts, penetrating fragments and bullets (including parts of bullets) and BHBT. It was commissioned by Defence Equipment and Support (DE&S; UK MOD).
Method
A systematic review of the open literature was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. The Web of Knowledge, Science Direct, Google Scholar and the Ballistic Injury Archive (BIA) were used to identify peer-reviewed journal and conference papers. The BIA was established in 1978 with the terms of reference to ‘maintain and update records of published works in the area of war wounds, explosive blast injury and wound ballistics etcetera’. The collection is available to Service and HM Government Officers and Research Establishments. US government reports were identified using the Defense Technical Information Center, an online depository of DoD and government funded research (http://www.dtic.mil/dtic/). The Barrington Digital Library, which is Cranfield University's Library at The Defence Academy of the United Kingdom (http://barrington.cranfield.ac.uk/), was also searched particularly for MSc and PhD theses of interest. Finally, a full set of the Personal Armour Systems Symposium (PASS) proceedings was hand-searched; PASS started in 1990 as the Ballistic Testing of Personal Armour Symposium (BTPA). In this PRISMA review, proceedings from BTPA1990 to PASS2012 (inclusive) were consulted. At the time of writing, PASS proceedings were only accessible to attendees of the symposia as a digital database of conference paper titles and abstracts did not exist. A full set of proceedings can be accessed via The Barrington Library.
Keywords used for these searches were military, helmet, head, impact, behind helmet blunt trauma, behind armour blunt trauma, BABT, BHBT, non-ballistic, blunt, ballistic, fragment and bullet. Reference lists from articles, reports, theses and conference papers identified were hand-searched to identify additional resources. Only primary sources were used in the literature review.
Results
Fifty-four sources included pertinent information relevant to this systematic review on military head injuries; no other systematic reviews on the subject were identified (Figure 1). Specifically, 40 journal articles, eight conference papers, two reports and two books were identified (four chapters were used from one book).
Results of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) review.
No incidents of a BHBT injury (since the adoption of composite helmets) were located in the literature. There is significant information in the forensic and medical literature regarding penetrating ballistic head injuries to civilians, however, the ammunition used (when described) is typically handgun or shotgun (particularly with reference to suicides). More unusual penetrating head injuries from impalements are also the subject of case studies within the forensics literature,14 ,15 but is not reviewed further due to the lack of relevance to military injuries. Data obtained for non-ballistic (Table 1) and ballistic head injuries (Table 2) are summarised.
Non-ballistic head injuries suffered by military personnel
Ballistic head injuries suffered by military personnel
Discussion
The human skull comprises of 22 bones (usually divided into the cranial and facial bones) and accounts for approximately 9% of the human body. While this is a relatively small percentage, the skull protects the brain and thus understanding the cause and severity of head injuries is vital; such information may inform future research in a number of key areas including, but not limited to, protection and medical interventions.
This article reviews the openly accessible literature regarding non-ballistic, penetrating and BHBT head injuries suffered by military personnel. The risk of BHBT injuries is widely referred to, but there is no evidence of their occurrence in the literature thus they are not discussed further.
Information regarding non-ballistic head injuries that occur to military personnel is limited. An assessment of non-ballistic head injuries during combat appears limited to that conducted for the first Gulf War in 1991; the data suggested a decrease in number and severity of injuries compared with non-combat data and the authors assumed this decrease was due to helmet use during combat scenarios. UK combat helmets have provided non-ballistic impact protection for >30 years; other nations also provide such protection but typically at a lower level compared with British helmets. Some British and international data exists for military parachutists, where it can be assumed that helmets were worn during these events; if so the relatively low injury rates recorded can in part be attributed to suitable helmet design—although training is of course paramount.
There are a number of issues with the openly accessible literature identified and summarised in this systematic review. One of the most fundamental issues of the definition of ‘the head’ varies among authors with many not distinguishing between the head, which is typically considered to be the area covered by a combat helmet, and face and neck injuries; calls for this to be rectified date back to 1991.38 The precise position of the injury and the long-term outcome is rarely given and the use of the words ‘injuries’ and ‘casualties’ also varies among papers; it is not always clear if the use of these words include fatalities or if, among a group of personnel, more than one injury has occurred.
The nationality of the injured is not always given, and such information might allow some assumptions to be made regarding the wearing (or not) of personal protective equipment (PPE) such as body armour, helmets and eye/face protection and potentially of a cause of injury (particularly when discussing rifle ammunition). The wearing of such PPE is rarely explicitly stated or described and when PPE is discussed there are usually brief comments regarding effectiveness (in the author’s opinion) or suggestions for improvements. Data are in different formats, for example, actual numbers and percentages; total numbers are often not provided. The cause of the injuries/fatalities designated as ballistic injuries is typically described as fragments (blast) or bullets; rarely is a full breakdown provided. This forensic aspect of injury would be incredibly useful to designers of PPE. Overall, comparison among the different sources is, therefore, difficult beyond general statements. What is clear is that approximately 20% of penetrating military injuries occur to the head (ie, the skull is penetrated, and therefore, excluding the neck). Considering the last 30 years of conflict these penetrating ballistics injuries account for approximately 40%–50% of combat fatalities.
The data does suggest that ballistic head injuries suffered by military personnel are primarily due to fragmentation (traditional munitions and IEDs). Assuming combat helmets are worn, these injuries will usually affect the face and neck (if not protected), as modern military helmets primarily provide protection from fragments. Ballistic impacts involving bullets (which are more likely to kill) are typically due to impacts to the face and to events that perforate helmets. However, the literature suggests that wearing military helmets reduces fatalities. The anterior of the head and the temporal region are reportedly particularly vulnerable to penetrating injuries.
Conclusions
The accessible literature regarding non-ballistic and ballistic head injuries suffered by military personnel clearly illustrates that wearing a combat helmet protects the brain, reducing severity of injury and reducing fatalities. Fatal head injuries are primarily due to bullets overmatching helmets or from fragments penetrating through the face. The literature refers to risk from BHBT injuries, but no evidence for such injuries was identified in this review; however, it should be noted that there may be sources of information in restricted-access government reports.
References
Footnotes
Contributors EL commissioned this review which was conducted by DJC and IH. DJC wrote the manuscript which was commented on by EL and IH.
Funding DE&S (PCE/00040).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.