Development of a skull/brain model for military wound ballistics studies.

Reports on penetrating ballistic head injuries in the literature are dominated by case studies of suicides; the penetrating ammunition usually being .22 rimfire or shotgun. The dominating cause of injuries in modern warfare is fragmentation and hence, this is the primary threat that military helmets protect the brain from. When helmets are perforated, this is usually by bullets. In combat, 20% of penetrating injuries occur to the head and its wounding accounts for 50% of combat deaths. A number of head simulants are described in the academic literature, in ballistic test methods for helmets (including measurement of behind helmet blunt trauma, BHBT) and in the 'open' and 'closed' government literature of several nations. The majority of these models are not anatomically correct and are not assessed with high-velocity rifle ammunition. In this article, an anatomically correct 'skull' (manufactured from polyurethane) and 'brain' (manufactured from 10%, by mass, gelatine) model for use in military wound ballistic studies is described. Filling the cranium completely with gelatine resulted in a similar 'skull' fracture pattern as an anatomically correct 'brain' combined with a representation of cerebrospinal fluid. In particular, posterior cranial fossa and occipital fractures and brain ejection were observed. This pattern of injury compared favourably to reported case studies of actual incidents in the literature.

Comparing the comfort and potential military performance restriction of neck collars from the body armor of six different countries.

The aim of this trial was to undertake an assessment of ballistic neck collars to assess comfort and potential military performance restriction. Neck collars from six different countries were procured with 71 U.K. servicemen assessing two randomly allocated collars to rate one against the other. 58% of participants had worn UK neck collars previously on exercise, but only 6% had used them on operational tours. Body armor with shorter and thinner collars was rated the most comfortable, despite lying close to the neck. It was easier to aim a rifle wearing collars with overlapping segments, especially when in the prone position. Although higher and more rigid collars fared worse overall, this could potentially be offset by the higher levels of ballistic protection they provide. There is a need to evaluate other methods of protecting the neck such as nape protectors and ballistic scarves in combination with the use of backpacks and biometric data collection. Currently, there exists no agreed method of performing ergonomic (or human factor) assessments of the varying components of military body armor systems. Published standards for the minimum military performance requirements of the various components of body armor, including neck collars, need to be established.

Evaluation of bone excision effects on a human skull model - I: Mechanical testing and digital image correlation.

The mechanisms of skull impact loading may change following surgical interventions such as the removal of bone lesions, but little is known about the consequences in the event of subsequent head trauma. We, therefore, prepared acrylonitrile butadiene styrene human skull models based on clinical computed tomography skull data using a three-dimensional printer. Six replicate physical skull models were tested, three with bone excisions and three without. A drop tower was used to simulate the impact sustained by falling backwards onto the occipital lobe region. The impacts were recorded with a high-speed camera, and the occipital strain response was determined by digital image correlation. Although the hole affected neither the magnitude nor the sequence of the fracture pattern, the digital image correlation analysis highlighted an increase in strain around the excised area (0.45%-16.4% of the principal strain). Our approach provides a novel method that could improve the quality of life for patients on many fronts, including protection against trauma, surgical advice, post-operative care, advice in litigation cases, as well as facilitating general biomechanical research in the area of trauma injuries.

Sharp and blunt force trauma concealment by thermal alteration in homicides: An in-vitro experiment for methodology and protocol development in forensic anthropological analysis of burnt bones.

Burning of human remains is one method used by perpetrators to conceal fatal trauma and expert opinions regarding the degree of skeletal evidence concealment are often disparate. This experiment aimed to reduce this incongruence in forensic anthropological interpretation of burned human remains and implicitly contribute to the development of research methodologies sufficiently robust to withstand forensic scrutiny in the courtroom. We have tested the influence of thermal alteration on pre-existing sharp and blunt trauma on twenty juvenile sheep radii in the laboratory using an automated impact testing system and an electric furnace. The testing conditions simulated a worst-case scenario where remains with pre-existing sharp or blunt trauma were exposed to burning with an intentional vehicular fire scenario in mind. All impact parameters as well as the burning conditions were based on those most commonly encountered in forensic cases and maintained constant throughout the experiment. The results have shown that signatures associated with sharp and blunt force trauma were not masked by heat exposure and highlights the potential for future standardization of fracture analysis in burned bone. Our results further emphasize the recommendation given by other experts on handling, processing and recording burned remains at the crime scene and mortuary.

The effect of knife handle shape on stabbing performance.

A quantitative knowledge of stabbing ability is a pre-requisite to establishing protection standards for stab resistant body armour. In order to determine the validity of measurements it is necessary to understand all the mechanisms that determine performance. This paper describes a series of tests that were performed in order to determine the effect of handle size and shape on the forces and impact energy that could be produced during stabbing of an armoured target. It was found that the single largest variable was that of the test participants with all other variables such as handle size and shape having only slight effects on the magnitude of impact energy. The use of a finger guard or hilt was shown to increase the mean energy delivered to the target by approximately 5J compared to a handle having no guard. It was also found that the characteristics of energy delivery were strongly influenced by the position of the grip relative to this guard. This reinforces the conclusions of previous work (Horsfall et al., 1999; Chadwick et al., 1999) on the serial nature of momentum transfer during a stabbing impact.

Remote ballistic fractures in a gelatine model--aetiology and surgical implications.

BACKGROUND: Remote ballistic femoral fractures are rare fractures reported in the literature but still debated as to their existence and, indeed, their treatment. This study aimed to prove their existence, understand how they occur and determine which ammunition provides the greatest threat. In addition, fracture patterns, soft tissue disruption and contamination were assessed to aid in treatment planning. METHOD: We filmed 42 deer femora embedded in ballistic gelatine and shot with four different military (5.56 × 45 mm, 7.62 × 39 mm) and civilian (9 × 19 mm, .44 in.) bullets, at varying distances off the bone (0-10 cm). RESULTS: Two remote ballistic fractures occurred, both with .44 in. hollow-point bullets shot 3 cm off the bone. These fractures occurred when the leading edge of the expanding temporary cavity impacted the femur's supracondylar region, producing a wedge-shaped fracture with an undisplaced limb, deceivingly giving the appearance of a spiral fracture. No communication was seen between the fracture and permanent cavity, despite the temporary cavity encasing the fracture and stripping periosteum from its base. CONCLUSION: These fractures occur with civilian ammunition, but cannot prove their existence with military rounds. They result from the expanding temporary cavity affecting the weakest part of the bone, creating a potentially contaminated wedge-shaped fracture, important for surgeons considering operative intervention.

Clothing increases the risk of indirect ballistic fractures.

BACKGROUND: Current literature has shown the mechanism of how indirect fractures occur but has not determined what factors increase the risks of such fractures. The objective of this study is thus to determine the effect of clothing and soft tissue thickness on the risk of indirect fracture formation. METHODS: Twenty-five fresh red deer femora embedded in ballistic gelatine were shot with varying distances off their medial cortex with a 5.56 × 45 mm North Atlantic Treaty Organization (NATO) bullet while being filmed with a slow-motion video. We compared the effect of two different gelatine depths and the effect of denim cloth laid onto the impact surface of the moulds. RESULTS: Bullet passage in thinner moulds failed to cause fracture because the bullet exited the mould before a large expanding temporary cavity was produced. Clothing dramatically altered the size and depth of the expanding cavity, as well as increased lateral pressures, resulting in more severe fractures with greater bullet distances from the bone that can cause fracture. CONCLUSIONS: Clothing increases the risk of indirect fracture and results in larger, more superficial temporary cavities, with greater lateral pressures than are seen in unclothed specimens, resulting in more comminuted fractures. Greater tissue depth affords the 5.56 × 45 mm NATO a chance to yaw and thus develop an enlarging temporary cavity that is sufficient to cause fracture.