Ocular biomechanics due to ground blast reinforcement

BACKGROUND AND OBJECTIVE

Bomb blast injuries exerts a shearing force on the air-tissue interfaces, causing devastating ocular injury from the blast wave. Improvised explosive devices (IEDs) are usually placed at different heights from the ground to induce more severe injury through ground blast reinforcement (GBR). However, there is still a lack of knowledge of the role of GBR and IED height from the ground on ocular biomechanics, and how they can affect the intraocular pressure (IOP) in the eye. This study aimed to estimate the IOP due to frontal IED explosion at different heights from the ground using a fluid-structure interaction model with and without GBR effects.

METHODS

A 2 kg IED was placed within 5 m of the victim at 5 different heights from the ground, including 0, 0.42, 0.85, 1.27, and 1.70 m. Two different blast formulations were used to simulate the IED explosion: (a) spherical airburst, with no amplification of the initial shock wave due to interaction with the ground-surface, and (b) hemispherical surface-burst, where the initial blast wave is immediately reflected and reinforced by the ground (GBR).

RESULTS

Results revealed that the blast wave due to GBR reaches to the skull prior to the IED blast itself. The GBR also reached to the skull ∼ 0.6 ms earlier when the IED was on the ground compared to the height of 1.70 m. The highest and lowest IOPs of ∼ 17,000 and ∼ 15,000 mmHg were observed at the IED heights of 1.70 and 0 m from the ground considering GBR. However, when the role of the GBR is ignored, IOP of ∼ 9,000 mmHg was observed regardless of the IED height from the ground. The deformation in the apex of the cornea was higher when considering the GBR (∼ 0.75 cm) versus no GBR (∼ 0.65 cm). Considering GBR led to higher stresses and strains in the sclera.

CONCLUSIONS

When the role of GBR was ignored, the results showed similar patterns and magnitudes of stresses and deformations in the skull and eye regardless of the height of the IED from the ground, which was not the case when GBR was considered. The findings of this study suggest the critical role of GBR in ocular blast simulations.

Blunderbuss: Ocular and Orbital Injuries Due to Muzzle-Loading Firearms

PURPOSE

Injury to the eye and/or orbital and adnexal structures associated with antiquated muzzle-loading firearms has not, to our knowledge, been characterized with the exception of a single case report.

METHODS

A retrospective chart review of 7 patients treated at Vanderbilt University Medical Center from 2003 to 2017 who sustained traumatic injuries to the ocular and/or orbital structures secondary to the discharge of muzzle-loading firearms. The study was approved by the Vanderbilt Institutional Review Board.

RESULTS

In 6/7 cases, injuries occurred secondary to the muzzle-loading firearm exploding due to dysfunction or misuse. Foreign material deriving from the firearm was retained in 3/7 patients. Initial examination of the orbit and adnexa revealed 5/7 individuals sustaining orbital fractures and 6/7 with facial lacerations (including 2 with eyelid lacerations); none had evidence of a lacrimal duct injury. Three patients suffered globe injuries (1 closed-globe and 2 open-globe). Visual acuity at last follow-up was ≥20/20 in 12/14 eyes examined. Surgical intervention was required in the treatment of 4/7 individuals (including 3/7 requiring intervention for sustained orbital fractures). No individuals were wearing eye protection at the time of injury. All individuals survived their injuries.

CONCLUSIONS

The operation of muzzle-loading firearms poses a unique risk of injury to the operator. The resultant injuries in this case series were primarily due to the explosion of the firearm, which subsequently appear similar to orbital and ocular blast injuries caused by explosive weapons. Orbital injuries and more potentially more devastating ocular injuries may have been prevented by protective eyewear.

Urgent Subconjunctival Needle Decompression for Orbital Compartment Emphysema Caused by Compressed Air Injury

Orbital compartment syndrome is a critical ophthalmic emergency that needs urgent diagnosis and treatment to prevent permanent vision loss caused by optic nerve compression or retinal ischemia. In this article, we present a child with orbital compartment syndrome caused by orbital emphysema as a result of a rare type of ocular trauma and introduce a simple technique to decompress the pressure. The patient was a 4-year-old boy who experienced a compressed air blast to his left eye. He presented to the emergency department with a frozen globe, tight orbit, and chemosis, without any evidence of globe rupture, conjunctival laceration, and orbital bone fracture. Computed tomographic scan demonstrated extensive subcutaneous, intraorbital, and intracranial emphysema. The pressure was immediately relieved under intravenous sedation by inserting a 27-gauge needle into the chemotic subconjunctival space at the lower lid fornix, followed by gentle manipulation of the globe to help the air escape through the needle. Compressed air injury is a rare type of orbital trauma, and this patient constituted the youngest case ever reported in the English literature, to our knowledge. Air decompression through the conjunctiva as described in this article is a useful technique that can be applied by emergency medicine specialists with special caution for patients with orbital compartment syndrome and orbital emphysema caused by compressed air injury.

Firecracker eye exposure: experimental study and simulation

Understanding the mechanisms of traumatic ocular injury is helpful to make accurate diagnoses before the symptoms emerge and to develop specific eye protection. The comprehension of the dynamics of primary blast injury mechanisms is a challenging issue. The question is whether the pressure wave propagation and reflection alone could cause ocular damage. To date, there are dissenting opinions and no conclusive evidence thereupon. A previous numerical investigation of blast trauma highlighted the dynamic effect of pressure propagation and its amplification by the geometry of the bony orbit, inducing a resonance cavity effect and a standing wave hazardous for eye tissues. The objective of the current work is to find experimental evidence of the numerically identified phenomenon. Therefore, tests aimed at evaluating the response of porcine eyes to blast overpressure generated by firecrackers explosion were performed. The orbital cavity effect was considered mounting the enucleated eyes inside a dummy orbit. The experimental measurements obtained during the explosion tests presented in this paper corroborate the numerical evidence of a high-frequency pressure amplification, enhancing the loading on the ocular tissues, attributable to the orbital bony walls surrounding the eye.

Expanding Hematoma's Life-Threatening Neck and Face Emergency Management of Ballistic Injuries

This article aims to bring attention to the morbidity and fatality of hemorrhage, how expanding hematoma and air compromise neck/face N/F injuries and present challenges. Large neck vessel ballistic injuries may lead to hemorrhage and expanding hematoma, resulting in airway compromise, due to injuries to the internal and/or external carotid arteries, internal jugular veins "internal carotid artery, external carotid artery, internal jugular vein," and the external carotid artery deep branches. This also leads to injuries to the cervical fascial layers (barriers of deep spaces) that facilitate pooling blood and hematoma into compartmental and large potential space which effects the pharynx, larynx, esophagus, and trachea.The expanding hematomas distort neck anatomical landmarks so "no neck zones" classifications are applicable. As the spectrum of injuries continues to evolve, the clinical characterization needs a new categorization based on compartmental hematoma and potential space anatomical location like retropharyngeal, parapharyngeal, sublingual, submandibular spaces, retrobulbar, and cheek compartment space hematomas.Presence of symptoms and location of the hematoma generally dictate what type of procedure is needed and how urgently it needs to be appropriately performed.Two unusual patients of pseudoaneurysms facial artery injuries with extravasation of blood producing a pulsating hematoma are referred to. Another patient considers large internal carotid artery injuries pseudoaneurysms revealed in angiography.The immediate management of life-saving patients requires aggressive airway maintenance at the scene, conscious victim will often obtain a posture that clears his airway and the semiconscious or unconscious put him in prone position. Air compromise may need emergency intubation, large bore cannula cricothyroidotomy, cricothyrotomy and at medical facilities tracheostomy.

Thermal shell fragment craniofacial injury: biophysics, pathophysiology, and management

This article aims to bring attention to unique risks and burns by thermal shell fragment craniofacial soft tissue injury. Hot shrapnel may inflict burns to major vessel walls and lead to life-threatening hemorrhaging or death, which adds a new challenge for craniofacial surgeons. Morbidity of thermal deep tissue may lead to deep tissue necrosis and infection.Thermal energy (TE) physics, biophysics, and pathophysiological effects relate directly to the amount of heat generated from shell casing detonation, which transfers to skin, deep tissue, as well as brain and leads to life-threatening burning of organs; this is different from shrapnel kinetic energy injury.The unprecedented increase in using a large range of explosives and high-heat thermobaric weapons contributes to the superfluous and unnecessary suffering caused by thermal injury wounds.Surgeons and medics should recognize that a surprising amount of TE can be found in an explosion or detonation of a steel-encased explosive, resulting in TEs ranging from 400 F up to 1000 F.

Anterior segment imaging in combat ocular trauma

Purpose. To evaluate the use of ocular imaging to enhance management and diagnosis of war-related anterior segment ocular injuries. Methods. This study was a prospective observational case series from an ongoing IRB-approved combat ocular trauma tracking study. Subjects with anterior segment ocular injury were imaged, when possible, using anterior segment optical coherence tomography (AS-OCT), confocal microscopy (CM), and slit lamp biomicroscopy. Results. Images captured from participants with combat ocular trauma on different systems provided comprehensive and alternate views of anterior segment injury to investigators. Conclusion. In combat-related trauma of the anterior segment, adjunct image acquisition enhances slit lamp examination and enables real time In vivo observation of the cornea facilitating injury characterization, progression, and management.

Management of penetrating medial and retro-bulbar orbital shrapnel/bullet injuries

The presence of shrapnel or a bullet lying in the medial orbital and retrobulbar area is rare. A review of the literature revealed only a few reports. Recently eye/orbital penetrating trauma has increased dramatically, mainly due to IEDs or conventional weaponry in civilian and military casualties. Our experience in the management of these types of injuries prompted this report. Practical techniques for correctly determining the location of retained projectiles in the orbit are described. Surgical techniques for treatment are presented, based on safe and successful practices used in the missile retrievals. Six shrapnel and three bullet injuries, mostly in the medial orbital region, were removed without increasing morbidity and with limited orbital tissue injury.

Maxillofacial air-containing cavities, blast implosion injuries, and management

PURPOSE

Distinctive mechanisms of primary blast effects have produced a transitional era of facial trauma. Implosion mechanism damage is one of these. Implosion mechanism damage results in injury limited to the gas-containing structures of the auditory canal, paranasal sinuses, gastrointestinal tract, and lungs. Worldwide, the victims of explosive detonations have increased and advanced dramatically. The outcome is greater mortality and morbidity and new types of injuries, especially in the maxillofacial region. Thus, the knowledge of, and experience with, their management should be shared globally by colleagues through publications.

MATERIALS AND METHODS

The implosion and mini re-explosion of compressed air sinuses leads to skeletal crush injury to the nasal-orbital-ethmoidal, maxillary sinuses, and nasal bones. A variety of surgical approaches were used successfully under conditions of war. The assessment of the associated injuries to the lung and/or brain is the initial priority to any life-threatening blast injury. This article describes the biophysical results of blast injuries to the middle third facial skeleton and associated injuries and details the management and protection of crushed air containing paranasal spaces.

RESULTS

Easy, simple, and fast treatment and management were used successfully on the pulverized, fragmented skeletal architecture of the facial middle part without increasing morbidity and with the avoidance of unnecessary surgical trauma.

CONCLUSIONS

Injuries in one of the most difficult esthetic, physiologic, and anatomic regions of the body is best treated with an understanding of the biophysical effects of the implosion mechanism on air-containing spaces in the maxillofacial region. The introduction of new methods for the management of severe destruction of hard and soft tissue will decrease the incidence of complications and the operative time.