Environment at the time of injury determines injury patterns in pelvic blast

Abstract

The use of explosives by terrorists, or during armed conflict, remains a major global threat. Increasingly, these events occur in the civilian domain, and can potentially lead to injury and loss of life, on a very large scale. The environment at the time of detonation is known to result in different injury patterns in casualties exposed to blast, which is highly relevant to injury mitigation analyses. We describe differences in pelvic injury patterns in relation to different environments, from casualties that presented to the deployed UK military hospitals in Iraq and Afghanistan. A casualty on foot when injured typically sustains an unstable pelvic fracture pattern, which is commonly the cause of death. These casualties die from blood loss, meaning treatment in these should focus on early pelvic haemorrhage control. In contrast, casualties injured in vehicle present a different pattern, possibly caused by direct loading via the seat, which does not result in pelvic instability. Fatalities in this cohort are from injuries to other body regions, in particular the head and the torso and who may require urgent neurosurgery or thoracotomy as life-saving interventions. A different strategy is therefore required for mounted and dismounted casualties in order to increase survivors.

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

“…Battlefield data has shown unstable pelvic fracture patterns consisting of PS and SI joint disruption, with posterior pelvic bleeding, as characteristic of the most severe pattern of dismounted blast injury 13,28,29. Our model has reproduced this pattern of injury with PS and SI disruption, unstable fracture patterns and vascular injury occurring posteriorly at the bifurcation of the external and internal iliacs.…”

“…These findings, corroborated by battlefield data,13,28,29 suggest that limb flail is likely a cause for an unstable pelvic fracture with posterior pelvic bleeding to occur in dismounted victims of an explosive insult.…”

“…A leading risk factor for increased mortality in dismounted blast injury is that of pelvic fracture, with an associated mortality of 60.8% compared to 22.9% in casualties without a pelvic fracture 30. Pelvic fracture patterns are of a mechanically unstable nature, characterised by an open pelvic fracture with disruption at the pubic symphysis (PS) and sacroiliac (SI) joints 29. The most common cause of death in dismounted pelvic blast injury is exsanguination, with uncontrolled haemorrhage from proximal large vessel trauma 13,24.…”

A New Understanding of the Mechanism of Injury to the Pelvis and Lower Limbs in Blast

“…The combination of the findings in these two studies consequently allow us to explain fully the mechanism of pelvic injury of the dismounted casualty: lower limb flail (tertiary blast injury) results principally in pubic symphysis and sacroiliac joint disruption with vascular injury whilst high velocity sand blast (secondary blast injury) results principally in pubic rami fractures (with associated posterior pelvic disruption), sacral and acetabular fractures. This mechanism of injury explains the observation from battlefield data and suggests that pelvic fractures seen following dismounted blast are due to both secondary (sand blast) and tertiary (lower limb flail) blast-injury modalities (Oh et al, 2016;Webster et al, 2018;Rankin et al, 2019).…”

“…All pelvic fractures sustained in this study were rotationally and vertically unstable, correlating with battlefield and clinical data. Pelvic fractures secondary to blast in the dismounted casualty are inherently unstable in nature, consisting of predominately pubic symphysis and sacroiliac joint disruption followed by pubic rami, sacral and acetabular fractures (Oh et al, 2016;Webster et al, 2018;Rankin et al, 2019). A previous mouse model demonstrated a link between shock-tube mediated outward flail of the lower limbs and displaced pelvic fractures with vascular injury (Rankin et al, 2019).…”