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

Insights and mechanics-driven modeling of human cutaneous impact injuries

Cutaneous damage mechanisms related to dynamic fragment impacts are dependent on the impact angle, impact energy, and fragment characteristics including shape, volume, contact friction, and orientation. Understanding the cutaneous injury mechanism and its relationship to the fragment parameters is lacking compromising damage classification, treatment, and protection. Here we develop a high-fidelity dynamic mechanics-driven model for partial-thickness skin injuries and demonstrate the influence of fragment parameters on the injury mechanism and damage sequence. The model quantitatively predicts the wound shape, area, and depth into the skin layers for selected impact angles, kinetic energy density, and the fragment projectile type including shape and material. The detailed sequence of impact damage including epidermal tearing that occurs ahead of the fragments initial contact location, subsequent stripping of the epidermal/dermal junction, and crushing of the underlying dermis are revealed. We demonstrate that the fragment contact friction with skin plays a key role in redistributing impact energy affecting the extent of epidermal tearing and dermal crushing. Furthermore, projectile edges markedly affect injury severity dependent on the orientation of the edge during initial impact. The model provides a quantitative framework for understanding the detailed mechanisms of cutaneous damage and a basis for the design of protective equipment.

Neuromuscular ultrasound findings in gunshot wounds

INTRODUCTION/AIMS

A spectrum of peripheral nerve injuries is associated with gunshot wounds (GSWs). Due to Wallerian degeneration, distal nerve lesions may go undetected on electrodiagnostic (EDX) testing. In patients with GSW undergoing high-resolution ultrasound (HRUS) for evaluation of neurological deficits, we have observed distal nerve morphological changes, but these have not been systematically studied. The aim of this study was to characterize changes on HRUS in nerves at and distal to gunshot injuries and to identify the frequency with which these changes occur.

METHODS

A retrospective cohort study was performed on patients referred for HRUS with peripheral nerve injuries from GSW. The primary injured nerve(s) were assessed along with distal segments of the same nerve and those of adjacent nerves. Findings were also compared to EDX studies.

RESULTS

Twenty-two of the 28 nerves injured proximally by GSW were evaluated distally and of these, 68% showed abnormal ultrasound findings, including enlarged cross sectional area (59%), fascicular enlargement (50%), and decreased nerve echogenicity (59%). In 17 patients, adjacent nerves were evaluated and 8 of the patients (47%) showed abnormalities in at least one distal adjacent nerve, including enlarged cross sectional area (41%), fascicular enlargement (41%), and decreased nerve echogenicity (35%).

DISCUSSION

This study demonstrated morphological changes at the site of the GSW but also in distal nerve segments including nerve enlargement, fascicular enlargement, and changes in nerve echogenicity. The complementary use of HRUS with EDX was highlighted in evaluation of GSW victims to assess the extent of peripheral nerve injury.

Surface wave analysis of the skin for penetrating and non-penetrating projectile impact in porcine legs

Secondary blast injuries may result from high-velocity projectile fragments which ultimately increase medical costs, reduce active work time, and decrease quality of life. The role of skin penetration requires more investigation in energy absorption and surface mechanics for implementation in computational ballistic models. High-speed ballistic penetration studies have not considered penetrating and non-penetrating biomechanical properties of the skin, including radial wave displacement, resultant surface wave speed, or projectile material influence. A helium-pressurized launcher was used to accelerate 3/8″ (9.525 mm) diameter spherical projectiles toward seventeen whole porcine legs from seven pigs (39.53 ± 7.28 kg) at projectile velocities below and above V₅₀. Projectiles included a mix of materials: stainless steel (n = 26), Si₃N₄ (n = 24), and acetal plastic (n = 24). Tracker video analysis software was used to determine projectile velocity at impact from the perpendicular view and motion of the tissue displacement wave from the in-line view. Average radial wave displacement and surface wave speed were calculated for each projectile material and categorized by penetrating or non-penetrating impacts. Two-sample t-tests determined that non-penetrating projectiles resulted in significantly faster surface wave speeds in porcine skin for stainless steel (p = 0.002), plastic (p = 0.004), and Si₃N₄ ball bearings (p = 0.014), while ANOVA determined significant differences in radial wave displacement and surface wave speed between projectile materials. Surface wave speed was used to quantify mechanical properties of the skin including elastic modulus, shear modulus, and bulk modulus during ballistic impact, which may be implemented to simulate accurate deformation behavior in computational impact models.

Local Effect of Ballistic Fragments Embedded Along the Carotid Sheath of a Porcine Animal Model

INTRODUCTION

Energized ballistic fragments from improvised explosive devices were the most common cause of injury to coalition service personnel during conflicts in Iraq and Afghanistan. Surgical excision of retained fragments is not routinely performed unless there is a concern for injury to vital structures. However, no clear guidelines dictate when or if a fragment should be removed, reflecting a lack of objective evidence of their long-term effects. Using a porcine model, we aimed to evaluate changes to the carotid artery produced by retained fragments over time.

MATERIALS AND METHODS

Institutional Animal Care and Use Committee approval for all experiments was obtained before commencement of the study. Eighteen female swine (mean mass 62.0 ± 3.4 kg) were randomized into three study groups corresponding to the time of survival after implantation of ballistic fragments: 1, 6, and 12 weeks. Two animals from each group were randomly assigned to have one of the three different fragments implanted within the right carotid sheath in zones 1-3 of the neck. The left carotid served as the control. The vascular flow rate and arterial diameter were measured at each level before implantation and again after the survival interval. Baseline and interval angiograms were performed to identify gross vascular changes.

RESULTS

No abnormalities were identified on baseline or interval angiograms. No significant difference was found when the baseline was compared to interval measurements or when compared to the control side for all gross and physiological measures at 1 and 6 weeks (P = .053-.855). After 12 weeks, the flow and diameter changed significantly (P < .001-.03), but this significant change was found in both the control and affected carotid.

CONCLUSIONS

The lack of significant gross anatomical and physiological changes at 6 weeks postimplantation lends evidence toward the current policy that early removal of retained ballistic fragments around cervical vessels is not required. Changes were significant after 12 weeks which suggest that surveillance may be required; however, such changes could be explained by physiological animal growth.

Gunshot Wounds: Ballistics, Pathology, and Treatment Recommendations, with a Focus on Retained Bullets

As the epidemic of gunshot injuries and firearm fatalities continues to proliferate in the United States, knowledge regarding gunshot wound (GSW) injury and management is increasingly relevant to health-care providers. Unfortunately, existing guidelines are largely outdated, written in a time that high-velocity weapons and deforming bullets were chiefly restricted to military use. Advances in firearm technology and increased accessibility of military grade firearms to civilians has exacerbated the nature of domestic GSW injury and complicated clinical decision-making, as these weapons are associated with increased tissue damage and often result in retained bullets. Currently, there is a lack of literature addressing recent advances in the field of projectile-related trauma, specifically injuries with retained bullets. This review aims to aggregate the available yet dispersed findings regarding ballistics, GSW etiology, and treatment, particularly for cases involving retained projectiles.

[Orbital firearm injuries]

BACKGROUND

Injuries caused by firearms are fortunately rare in the field of ophthalmology. The treatment of an affected patient is a special challenge both ophthalmologically and emotionally.

METHODS

We report on seven consecutive cases of patients with an orbital gunshot injury who presented in a university hospital over a period of 11 years. The course of events leading to the injury with the weapon involved, the type of projectile, the injury pattern, cranial imaging, treatment and course were evaluated.

RESULTS

A total of seven cases of injuries caused by firearms could be documented and evaluated in the period 2007-2018. All seven patients were male. The average age was 44 ± 27.5 years. Of the injuries five were caused by a suicide attempt and two by an accident. Firearms were used except for one injury caused by a crossbow. There was a retained projectile in four of the cases, the bullet went through the body in two cases and one of the cases presented with a ricochet shot. The final visual acuity was unilateral amaurosis in 1 case and bilateral amaurosis in another case, 1/35 (measured at 1 m) in 1 case, while it varied between 0.2 and 0.7 in the other 4 cases. No patient died as a direct consequence of the firearm injury.

CONCLUSION

Injuries caused by firearms are relatively rare in Germany and mostly have a suicidal background. The pattern of the injury of the ocular structures is very variable. A reconstruction attempt is principally recommended. In the care of patients interdisciplinary cooperation between ophthalmologists and neurosurgeons, orofacial surgeons, ear nose and throat (ENT) surgeons and psychiatrists is necessary.

Ballistic gelatin calibration standardisation

INTRODUCTION

A review of ballistic gelatin calibration standards has highlighted that data used from studies with different calibrations methods may not be able to be compared. Calibration of ballistic gelatin did not occur until the mid-1980s when Fackler recognised the deficiencies of uncalibrated gelatin. He determined that the calibration standard should be 85±5 mm of ball bearing penetration for a 180 m/s impact velocity. This study looks to improve on and optimise current ballistic gelatin calibration standards METHODS: Nine 0.177 cal (4.5 mm) spheres were fired using a Daisy Powerline air rifle at velocities between 134 m/s and 224 m/s at 25 gelatin blocks (n=225). Velocities were measured using an Oehler Model 36 Chronograph with three Model 57 screens. Depth of penetration (DoP) was measured from the entry surface to the back end of the sphere via a Mitutoyo Absolute vernier calliper.

RESULTS

The R-squared regression model showed that all batches had a close fit to the regression line. Using the R-squared regression model, the equation y=0.584x - 20.02 (where x is the velocity) returned a DoP of 84.918 mm for a 180 m/s impact and therefore needed minimal adjustment to align with Fackler's 85 mm DoP. The equation can be adjusted to y=0.584x - 20.12 to return a DoP of 85 mm for 180 m/s.

CONCLUSIONS

We propose that the calibration standard of ballistic gelatin with 4.5 mm spheres is DoP=0.584x - 20.12 where DoP is the depth of penetration (mm) and x is the impact velocity (m/s), The measured DoP should be within 5% of the calculated DoP.

Imaging Ballistic Injuries

Here in Canada, we often think of gun violence as confined to conflict zones, terrorism, and more of a problem for our southern neighbor. However, in recent years, it has also become a Canadian problem with increased gun violence related to criminal activity presenting in daily practice. Radiologists play a critical role in the evaluation of ballistic trauma and must therefore be familiar with both the common and uncommon patterns of ballistic injury. In this article, we review the mechanisms of ballistic trauma as well as their resultant injury patterns in order to guide image interpretation.

Case report of sudden death after a gunshot wound to the C2 vertebral bone without direct spinal cord injury: Histopathological analysis of spinal-medullary junction

Gunshot wounds (GSW) are one of the most common causes of penetrating spinal injury, however few data are available regarding GSW causing an indirect fatal nervous tissue injury, such as that induced by the concussive force secondary to the bullet penetration. This report describes a rare case of a death following a GSW spine injury at the level of C2 vertebral body, without direct contact with the spinal cord, as seen with computed tomography scan performed soon after the death. At autopsy, vertebral canal and dura mater, as well as spinal cord and medulla oblongata, appeared devoid of pathologies and/or lesions, major viscera were unaltered. The cause of death was attributed to a cardiorespiratory arrest subsequent to the GSW injury of the C2 vertebral bone. Histopathological analysis of spinal cord and medulla oblongata was performed by means of conventional stainings, and glial fibrillary acidic protein (GFAP) and Neurofilaments 200kD (NF) immunohistochemistry. Histological alterations stood out against a tissue with no other evident sign of neuropathology, and could be observed from the caudalmost part of the medulla oblongata to the level of the inferior olivary nucleus. Main structural changes were found in the white matter, involving often the adjacent gray matter, where they appeared as multiple scattered areas of degeneration, lacking the usual staining affinity, and showing a disrupted fibrillary pattern as evidenced by myelin staining, and GFAP- and NF-immunolabelling. The shock wave secondary to the impact on the C2 vertebral bone is likely to have been the cause of a widespread neuronal-axonal histopathological damage at the spinal-medullary junction and caudal medulla oblongata that is compatible with a severe fatal respiratory dysfunction and dysregulation of the autonomic pathways subserving the control of blood pressure and cardiac activity.

[Update on gunshot wounds to extremities]

Due to recent rampage and terror attacks in Europe, gunshot wounds have become a focus of attention even though they are still rare in Europe. Approximately 50% of gunshot wounds affect the extremities and to understand the sequelae, a basic knowledge of wound ballistics is indispensable. The energy transmitted from the bullet to the tissue is responsible for the severity of the injury and is dependent on the type of weapon and ammunition. A differentiation is made between low-energy injuries caused, e.g. by pistols and high-energy injuries mostly caused by rifles. The higher energy transfer to the tissue in high-energy injuries, results in a temporary wound cavity in addition to the permanent wound channel with extensive soft tissue damage. High-energy gunshot fractures are also more extensive compared to those of low energy injuries. Debridement seems to be necessary for almost all gunshot wounds. Fractures should be temporarily stabilized with an external fixator due to contamination.

Ophthalmic Injuries Related to Maxillofacial Trauma Due to Urban Warfare

: Midfacial trauma commonly causes ocular injuries of varying degrees. Eye injuries account for approximately 10% of all battle injuries. Severity of injuries may range from a subconjunctival haemorrhage to optic nerve injury and globe laceration and rupture.

AIM OF STUDY

Is to evaluate the associated ophthalmic injuries in maxillofacial trauma due to war and to emphasize the need for proper ophthalmic examination to exclude and manage any associated ophthalmic injuries.

MATERIALS AND METHODS

A total of 66 patients with maxillofacial trauma due to war were considered in this study and underwent classification of the fractures to know patterns of fractures and to specify the ophthalmic injuries which might be associated with each fracture. Referral to ophthalmologist was considered to determine the exact nature of ophthalmic injuries. Results by a maxillofacial surgeon and ophthalmologist were evaluated.

RESULTS

Midfacial trauma particularly those associated with zygomatic bone fracture was highly significant due to blast and bullets can lead to serious ophthalmic injuries. This was related to 57% of ophthalmic injuries. The related ocular injuries which were subconjunctival hemorrhage and the rupture or lacerated eye globe found to be highly significant war injuries while the preretinal hemorrhage and diplopia were significant.

CONCLUSION

A thorough proper ophthalmic examination should be carried out for every patient with these fractures and suspected cases should be placed under close observation so that immediate and active treatment can be taken if necessary.

Effect of ageing on the calibration of ballistic gelatin

PURPOSE

Ballistic gelatin is commonly used as a validated surrogate for soft tissue during terminal ballistic testing. However, the effect of a delay between production and testing of a gelatin mould remains unknown. The aim of this study was to determine any potential effects of ageing on ballistic gelatin.

METHODS

Depth of penetration (DoP) of 4.5 mm spherical fragment simulating projectiles was ascertained using mixtures of 10%, 11.25% and 20% Type A 250 Bloom ballistic gelatin. Testing was performed daily for 5 days using velocities between 75 and 210 m/s. DoP at day 5 was statistically compared with day 1, and net mass change was recorded daily.

RESULTS

No significant difference was found for DoP observed with time in any of the samples (P>0.05). Spearman correlation was excellent in all moulds. The moulds with known standard calibrations remained in calibration throughout the study period. Mass loss of less than 1% was noted in all samples.

CONCLUSION

Mass loss was the only quantifiable measure of changes in the blocks with time, but did not correlate with any changes in DoP. This may provide reassurance when undertaking such testing that an inadvertent delay will not significantly alter the penetration properties of the mould. Future research is recommended to determine any potential effect on the mechanical properties of gelatin at higher velocity impacts and whether the calibration corresponds to an adequate simulation under such conditions.

Assessment of bullet effectiveness based on a human vulnerability model

Introduction

Penetrating wounds from explosively propelled fragments and bullets are the most common causes of combat injury. There is a requirement to assess the potential effectiveness of bullets penetrating human tissues in order to optimise preventive measures and wound trauma management.

Methods

An advanced voxel model based on the Chinese Visible Human data was built. A digital human vulnerability model was established in combination with wound reconstruction and vulnerability assessment rules, in which wound penetration profiles were obtained by recreating the penetration of projectiles into ballistic gelatin. An effectiveness evaluation method of bullet penetration using the Abbreviated Injury Scale (AIS) was developed and solved using the Monte Carlo sampling method.

Results

The effectiveness of rifle bullets was demonstrated to increase with increasing velocity in the range of 300–700 m/s. When imparting the same energy, the effectiveness of the 5.56 mm bullet was higher than the 7.62 mm bullet in this model.

Conclusions

The superimposition of simulant penetration profiles produced from ballistic gelatin simulant has been used to predict wound tracts in damaged tissues. The authors recognise that determining clinical effectiveness based on the AIS scores alone without verification of outcome by review of clinical hospital records means that this technique should be seen more as a manner of comparing the effectiveness of bullets than an injury prediction model.

A correlation analysis of metacarpal & phalangeal injury pattern from improvised explosive devices amongst armed force personnel

Injuries to the hand during military combat operations, particularly from improvised explosive devices (IEDs) have a significant impact on form, function, mental health and future employment but remain underreported amidst the life and limb-threatening emergencies that garner more attention. An understanding the patterns of hand injuries encountered from IEDs is crucial to optimizing reconstruction and rehabilitation. The aim of this study was to re-evaluate hand injury sustained from IED in order to understand the clinical burden for reconstruction and direct the focus for future hand protection. We identified 484 hand injuries in 380 patients sustained as a result of IEDs among military personnel service in Afghanistan between 2006 and 2013. 53% of all surviving military personnel injured by IEDs sustain injuries to the hand. Analysis of the 103 patients who sustained injury to the metacarpal, phalanges or digital amputation revealed that the middle and ring fingers are most commonly injured. Amputation to the ring finger is strongly associated with injury to the adjacent fingers and amputations to the middle, ring and little fingers concurrently is a commonly observed pattern. The proximal phalanges of the middle and ring fingers had a strong correlation for fracture together. These findings disprove the conventional belief in an ulnar focus of injury and support the quest for a development of combat hand protection that addresses the injury pattern seen.

Injury representation against ballistic threats using three novel numerical models

Injury modelling of ballistic threats is a valuable tool for informing policy on personal protective equipment and other injury mitigation methods. Currently, the Ministry of Defence (MoD) and Centre for Protection of National Infrastructure (CPNI) are focusing on the development of three interlinking numerical models, each of a different fidelity, to answer specific questions on current threats. High-fidelity models simulate the physical events most realistically, and will be used in the future to test the medical effectiveness of personal armour systems. They are however generally computationally intensive, slow running and much of the experimental data to base their algorithms on do not yet exist. Medium fidelity models, such as the personnel vulnerability simulation (PVS), generally use algorithms based on physical or engineering estimations of interaction. This enables a reasonable representation of reality and greatly speeds up runtime allowing full assessments of the entire body area to be undertaken. Low-fidelity models such as the human injury predictor (HIP) tool generally use simplistic algorithms to make injury predictions. Individual scenarios can be run very quickly and hence enable statistical casualty assessments of large groups, where significant uncertainty concerning the threat and affected population exist. HIP is used to simulate the blast and penetrative fragmentation effects of a terrorist detonation of an improvised explosive device within crowds of people in metropolitan environments. This paper describes the collaboration between MoD and CPNI using an example of all three fidelities of injury model and to highlight future areas of research that are required.

[Therapy of a gunshot fracture to the midfoot]

We report on a soldier with a gunshot wound to the midfoot. The diaphysis of MT 5 was pounded to pieces and there was a fracture in the diaphysis of MT 4. After debridement and fixation of MT 4 and MT 5 to MT 2 and 3 via two Kirschner wires we conducted a second look procedure with reconstruction of MT 5 via a piece of iliac crest. After eight weeks of unloading and removal of the last wire we started to put successively heavier weight on the foot.

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.