The Mortality Peer Review Panel: a report on the deaths on operations of UK Service personnel 2002–2013

Pelvic Protection Limiting Lower Limb Flail Reduces Mortality

Pelvic blast injury is one of the most severe patterns of injury to be sustained by casualties of explosions. We have previously identified the mechanism of injury in a shock tube-mediated murine model, linking outward flail of the lower limbs to unstable pelvic fractures and vascular injury. As current military pelvic protection does not protect against lower limb flail, in this study we have utilized the same murine model to investigate the potential of novel pelvic protection to reduce injury severity. Fifty cadaveric mice underwent shock-tube blast testing and subsequent injury analysis. Pelvic protection limiting lower limb flail resulted in a reduction of pelvic fracture incidence from both front-on (relative risk (RR) 0.5, 95% confidence intervals (CIs) 0.3-0.9, p < 0.01) and under-body (RR 0.3, 95% CI 0.1-0.8 p < 0.01) blast, with elimination of vascular injury in both groups (p < 0.001). In contrast, pelvic protection, which did not limit flail, had no effect on fracture incidence compared to the control group and was only associated with a minimal reduction in vascular injury (RR 0.6, 95% CI 0.4-1.0, p < 0.05). This study has utilized a novel strategy to provide proof of concept for the use of pelvic protection, which limits limb flail to mitigate the effects of pelvic blast injury.

Establishing an enduring Military Trauma Mortality Review: Misconceptions and lessons learned

Under direction from the Defense Health Agency, subject matter experts (SMEs) from the Joint Trauma System, Armed Forces Medical Examiner System, and civilian sector established the Military Trauma Mortality Review process. To establish the most empirically robust process, these SMEs used both qualitative and quantitative methods published in a series of peer-reviewed articles over the last 3 years. Most recently, the Military Mortality Review process was implemented for the first time on all battle-injured service members attached to the United States Special Operations Command from 2001 to 2018. The current Military Mortality Review process builds on the strengths and limitations of important previous work from both the military and civilian sector. To prospectively improve the trauma care system and drive preventable death to the lowest level possible, we present the main misconceptions and lessons learned from our 3-year effort to establish a reliable and sustainable Military Trauma Mortality Review process. These lessons include the following: (1) requirement to use standardized and appropriate lexicon, definitions, and criteria; (2) requirement to use a combination of objective injury scoring systems, forensic information, and thorough SME case review to make injury survivability and death preventability determinations; (3) requirement to use nonmedical information to make reliable death preventability determinations and a comprehensive list of opportunities for improvement to reduce preventable deaths within the trauma care system; and (4) acknowledgment that the military health system still has gaps in current infrastructure that must be addressed to globally and continuously implement the process outlined in the Military Trauma Mortality Review process in the future. LEVEL OF EVIDENCE: Level III.

Pelvic injury patterns in blast: Morbidity and mortality

BACKGROUND

Pelvic trauma has emerged as one of the most severe injuries to be sustained by the victim of a blast insult. The incidence and mortality due to blast-related pelvic trauma is not known, and no data exist to assess the relative risk of clinical or radiological indicators of mortality.

METHODS

The UK Joint Theater Trauma Registry was interrogated to identify those sustaining blast-mediated pelvic fractures during the conflicts in Iraq and Afghanistan, from 2003 to 2014, with subsequent computed tomography image analysis. Casualties that sustained more severe injuries remote to the pelvis were excluded.

RESULTS

One hundred fifty-nine casualties with a 36% overall mortality rate were identified. Pelvic vascular injury, unstable pelvic fracture patterns, traumatic amputation, and perineal injury were higher in the dismounted fatality group (p < 0.05). All fatalities sustained a pelvic vascular injury. Pelvic vascular injury had the highest relative risk of death for any individual injury and an associated mortality of 56%. Dismounted casualties that sustained unstable pelvic fracture patterns, traumatic amputation, and perineal injury were at three times greater risk (relative risk, 3.00; 95% confidence interval, 1.27-7.09) to have sustained a pelvic vascular injury than those that did not sustain these associated injuries. Opening of the pubic symphysis and at least one sacroiliac joint was significantly associated with pelvic vascular injury (p < 0.001), and the lateral displacement of the sacroiliac joints was identified as a fair predictor of pelvic vascular injury (area under the receiver operating characteristic curve, 0.73).

CONCLUSION

Dismounted blast casualties with pelvic fracture are at significant risk of a noncompressible pelvic vascular injury. Initial management of these patients should focus upon controlling noncompressible pelvic bleeding. Clinical and radiological predictors of vascular injury and mortality suggest that mitigation strategies aiming to attenuate lateral displacement of the pelvis following blast are likely to result in fewer fatalities and a reduced injury burden.

LEVEL OF EVIDENCE

Prognostic, level III.

Systematic approach to delivering prolonged field care in a prehospital care environment

BACKGROUND

This article describes a novel patient care algorithm which provides a Role 1 (R1) medic with a structured approach to delivering prolonged field care (PFC) in a resource-limited environment. PFC is a vital component of the operational patient care pathway providing the continuum of care from completion of a primary survey to the delivery to hospital care. Future operational environments are likely to have more fragile or extended lines of communication, potentially delaying evacuation to hospital care. This delay may lead to increases in patient morbidity and mortality. Effective PFC offers an opportunity to improve patient outcomes and help mitigate against this risk.

METHODS

An initial prototype model of a PFC care process was developed using existing hospital-based guidance. A series of medical and trauma vignettes and best available evidence were used to refine the algorithm.

RESULTS

The algorithm has been designed be used in conjunction with patient specific clinical guidance making the approach generalisable for all patient groups. For UK military, clinical guidance is provided by clinical guidelines for operations. The algorithm can be downloaded into a convenient format to be used on mobile devices or printed as an aide memoire.

Shooting through windscreens: ballistic injury assessment using a surrogate head model-two case reports

A synthetic head model developed to reproduce military injuries was assessed in two different scenarios involving shooting through intermediate targets (a laminated vehicle windscreen in scenario 1 and a military helicopter windscreen in scenario 2) with 7.62 × 39-mm mild steel core (MSC) ammunition. The injury patterns resulting from the two scenarios were assessed by a military radiologist and a forensic pathologist with combat injury experience and found to be clinically realistic.

Restricting Lower Limb Flail is Key to Preventing Fatal Pelvic Blast Injury

Pelvic vascular injury in the casualty of an explosive insult is a principal risk factor for increased mortality. The mechanism of injury has not previously been investigated in a physical model. In this study, a small-animal model of pelvic blast injury with a shock-tube mediated blast wave was utilised and showed that lower limb flail is necessary for an unstable pelvic fracture with vascular injury to occur. One hundred and seventy-three cadaveric mice underwent shock-tube blast testing and subsequent injury analysis. Increasingly displaced pelvic fractures and an increase in the incidence of pelvic vascular injury were seen with increasing lower limb flail; the 50% risk of vascular injury was 66° of lower limb flail out from the midline (95% confidence intervals 59°–75°). Pre-blast surgical amputation at the hip or knee showed the thigh was essential to result in pelvic displacement whilst the leg was not. These findings, corroborated by clinical data, bring a paradigm shift in our understanding of the mechanism of blast injury. Restriction of lower limb flail in the human, through personal protective equipment, has the potential to mitigate the effects of pelvic blast injury.

Combat vascular injury: Influence of mechanism of injury on outcome

BACKGROUND

Haemorrhage is the leading cause of death on the battlefield. Seventy percent of injuries are due to explosive mechanisms. Anecdotally, these patients have had poorer outcomes when compared to those with penetrating mechanisms of injury (MOI). We wished to test the hypothesis that outcomes following vascular reconstruction were worse in blast-injured than non blast-injured patients.

METHODS

Retrospective cohort study. British and American combat casualties with arterial injuries sustained in Iraq or Afghanistan (2003-2014) were identified from the UK Joint Theatre Trauma Registry (JTTR). Eligibility included explosive or penetrating MOI, with follow-up to UK hospital discharge, or death. Outcomes were mortality, amputation, graft thrombosis, haemorrhage, and infection. Statistical analysis was performed using Pearson Chi-Square test, t-tests, ANOVA or non-parametric equivalent, and survival analyses.

RESULTS

One hundred and fifteen patients were included, 80 injured by explosive and 35 by penetrating mechanisms. Evacuation time, ISS, number of arterial injuries, age and gender were comparable between groups. Seventy percent of arterial injuries resulted from an explosive MOI. The explosive injuries group received more blood products (p = 0.008) and suffered more regions injured (p < 0.0001). Early surgical interventions in both were ligation (n = 36, 31%), vein graft (n = 33, 29%) and shunting (n = 9, 8%). Mortality (n = 12, 10%) was similar between groups. Differences in limb salvage rates following explosive (n = 17, 53%) vs penetrating (n = 13, 76.47%) mechanisms approached statistical significance (p = 0.056). Nine (28%) vein grafted patients developed complications. No evidence of a difference in the incidence of vein graft thrombosis was found when comparing explosive with non-explosive cohorts (p = 0.154).

CONCLUSIONS

The recorded numbers of vein grafts following combat arterial trauma in are small in the JTTR. No statistically-significant differences in complications, including vein graft thrombosis, were found between cohorts injured by explosive and non-explosive mechanisms.

The outcome of patients in traumatic cardiac arrest presenting to deployed military medical treatment facilities: data from the UK Joint Theatre Trauma Registry

Background

The UK military was continuously engaged in armed conflict in Iraq and Afghanistan between 2003 and 2014, resulting in 629 UK fatalities. Traumatic cardiac arrest (TCA) is a precursor to traumatic death, but data on military outcomes are limited. In order to better inform military treatment protocols, the aim of this study was to define the epidemiology of TCA in the military population with a particular focus on survival rates and injury patterns.

Methods

A retrospective database analysis of the UK Joint Theatre Trauma Registry was undertaken. Patients who were transported to a UK deployed hospital between 2003 and 2014 and suffered TCA were included. Those patients injured by asphyxiation, electrocution, burns without other significant trauma and drowning were excluded. Data included mechanism of injury, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS) for each body region and survival to deployed (Role 3) field hospital discharge.

Results

424 TCA patients were identified during the study period; median age was 23 years, with a median ISS of 45. The most common mechanism of injury was explosive (55.7%), followed by gunshot wound (38.9%), road traffic collision (3.5%), crush (1.7%) and fall (0.2%). 45 patients (10.6% (95% CI 8.0% to 13.9%)) survived to deployed (Role 3) hospital discharge. The most prevalent body region with a severe to maximum AIS injury was the head, followed by the lower limbs, thorax and abdomen. Haemorrhage secondary to abdominal and lower limb injury was associated with survival; traumatic brain injury was associated with death.

Conclusions

This study has shown that short-term survival from TCA in a military population is 10.6%. With appropriate and aggressive early management, although unlikely, survival is still potentially possible in military patients who suffer traumatic cardiac arrest.

Does preliminary optimisation of an anatomically correct skull-brain model using simple simulants produce clinically realistic ballistic injury fracture patterns?

Ballistic head injury remains a significant threat to military personnel. Studying such injuries requires a model that can be used with a military helmet. This paper describes further work on a skull-brain model using skulls made from three different polyurethane plastics and a series of skull ‘fills’ to simulate brain (3, 5, 7 and 10% gelatine by mass and PermaGel™). The models were subjected to ballistic impact from 7.62 × 39 mm mild steel core bullets. The first part of the work compares the different polyurethanes (mean bullet muzzle velocity of 708 m/s), and the second part compares the different fills (mean bullet muzzle velocity of 680 m/s). The impact events were filmed using high speed cameras. The resulting fracture patterns in the skulls were reviewed and scored by five clinicians experienced in assessing penetrating head injury. In over half of the models, one or more assessors felt aspects of the fracture pattern were close to real injury. Limitations of the model include the skull being manufactured in two parts and the lack of a realistic skin layer. Further work is ongoing to address these.

Lessons from the organisation of the UK medical services deployed in support of Operation TELIC (Iraq) and Operation HERRICK (Afghanistan)

This paper provides the definitive record of the UK Defence Medical Services (DMS) lessons from the organisation of medical services in support of Operation (Op) TELIC (Iraq) and Op HERRICK (Afghanistan). The analysis involved a detailed review of the published academic literature, internal post-operational tour reports and post-tour interviews. The list of lessons was reviewed through three Military Judgement Panel cycles producing the single synthesis 'the golden thread' and eight 'silver bullets' as themes to institutionalise the learning to deliver the golden thread. One additional theme, mentoring indigenous healthcare systems and providers, emerged as a completely new capability requirement. The DMS has established a programme of work to implement these lessons.

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.

Combat related vascular injuries: Dutch experiences from a role 2 MTF in Afghanistan

BACKGROUND

In a combat environment, major vascular trauma endures as the leading cause of death. The Dutch role 2 Medical Treatment Facility (MTF), provided supportive care during the mission in Uruzgan, Afghanistan. Aim of this study was to conduct detailed analysis of the admitted major haemorrhages (vascular injuries) and to compare our findings with NATO coalition partners.

METHODS

Retrospective, descriptive study. Participants eligible for this study came from the role 2 MTF admission database, where they fitted the criteria 'Major haemorrhage (class 2 haemorrhage or more according to the ATLS(®) classification) between 2006 and 2010'. Results were contrasted with studies from coalition partners.

RESULTS

The query revealed 194 casualties sustaining 208 central (60% abdominal, 40% thoracic/neck), and 99 extremity major haemorrhages leading to 1.6 major haemorrhages per casualty. Survival was significantly better (p<0.05) in the peripheral vascular injuries cohort (96% versus 72%). Primary amputation was needed in 73/84 of lower, and in 8/15 of upper extremity major haemorrhages. Vascular repair or vascular Damage Control Surgery techniques (e.g. shunting) were used in 19/84 cases in the lower, and 7/15 in the upper extremity cohort, with a success rate of 69.2 percent. Amputation rates of coalition partners, using different inclusion and exclusion criteria, ranged from 5 to 60 percent.

CONCLUSIONS

Only in a few cases genuine peripheral vascular surgery was needed (<1%). This limited number of reconstructions does not demonstrate the need for extensive skills in all areas of vascular surgery. Achieved success rate until discharge was almost 70%. Vascular damage control surgery seems effective as initial limb saving skill in a role 2 MTF. The difference in usage of definitions concerning vascular injuries in current literature warrants further assessment. For optimal analysis there is need for detailed (NATO wide) registration with uniform definitions for vascular injuries.

LEVEL OF EVIDENCE

Level IV--Epidemiologic study.

Died of wounds: a mortality review

OBJECTIVES

Combat casualty care is a complex system involving multiple clinicians, medical interventions and casualty transfers. Improving the performance of this system requires examination of potential weaknesses. This study reviewed the cause and timing of death of casualties deemed to have died from their injuries after arriving at a medical treatment facility during the recent conflicts in Iraq and Afghanistan, in order to identify potential areas for improving outcomes.

METHODS

This was a retrospective review of all casualties who reached medical treatment facilities alive, but subsequently died from injuries sustained during combat operations in Afghanistan and Iraq. It included all deaths from start to completion of combat operations. The UK military joint theatre trauma registry was used to identify cases, and further data were collected from clinical notes, postmortem records and coroner's reports.

RESULTS

There were 71 combat-related fatalities who survived to a medical treatment facility; 17 (24%) in Iraq and 54 (76%) in Afghanistan. Thirty eight (54%) died within the first 24 h. Thirty-three (47%) casualties died from isolated head injuries, a further 13 (18%) had unsurvivable head injuries but not in isolation. Haemorrhage following severe lower limb trauma, often in conjunction with abdominal and pelvic injuries, was the cause of a further 15 (21%) deaths.

CONCLUSIONS

Severe head injury was the most common cause of death. Irrespective of available medical treatment, none of this group had salvageable injuries. Future emphasis should be placed in preventative strategies to protect the head against battlefield trauma.

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.

Refrigeration and freezing of porcine tissue does not affect the retardation of fragment simulating projectiles

Explosively propelled fragments are the most common cause of injury to UK service personnel in modern conflicts. Numerical injury models to simulate such injuries utilise algorithms based upon gelatin and animal tissue testing but data is limited on many fragment simulating projectiles and these simulants cannot represent human anatomy. Testing with post mortem specimens may overcome this limitation but no information exists about how post mortem tissue changes and storage conditions in humans or animals may affect projectile penetration. Two chisel nosed cylinders (0.49 g and 1.10 g) and a 0.51 g (5 mm) sphere were fired into three groups of porcine tissue (fresh, refrigerated and frozen then refrigerated) and compared to 20% gelatin. Depth of projectile penetration was ascertained with the assistance of computed tomography and kinetic energy absorption by tissues measured using Doppler radar and high speed photography. No difference in depth of penetration was found between porcine tissue stored in the different manners compared with 20% gelatin by impact velocities less than 100 m/s. Insufficient numbers of projectiles were retained in tissue at higher velocities for statistical analysis to be undertaken. Energy absorbed per millimetre of tissue ranged between 0.42 and 0.98 J/mm for different porcine tissue despite differing storage. This pilot study would suggest that the effect of refrigerating or freezing porcine tissue followed by thawing has no effect on its ability to retard these projectiles. Further research is required to ascertain if these results occur at greater velocities and for other types of projectile.