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BLOG: BB gun injuries are not to be considered lightly
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Read more blog posts from Mark R. Levine, MD
With summer upon us and more people than ever obtaining weapons for protection and enjoyment (target practice), it is worthwhile to summarize the danger of BB and pellet guns.
The term “ballistics” refers to the science of the travel of an object in flight. In the case of a gunshot wound or BB and pellet guns, the energy expended is kinetic energy, or energy due to a motion of bullet penetrating tissue and/or bone. The kinetic energy of a moving object is the function of its mass and its velocity so that KE=1/2 mv2.
It can be seen that increasing a mass only results in a linear increase in energy; however, increasing the velocity results in an exponential increase in energy to the second power.
There are some important considerations regarding BB and pellet guns. Both use compressed air or gas to propel steel balls, lead or plastic pellets. The air guns are powered by a spring piston, pneumatic or CO2. These methods are used in both air rifles and air pistols.
BB’s are made of steel with copper or zinc plating measuring 4.5 mm in diameter. Pellets can be made of lead or steel-tipped plastic and are generally 4.5 mm in diameter. Although most BB and pellet guns fire low-velocity missiles, they are still fast enough to penetrate the cranium, abdomen, thorax and paranasal sinuses. For example, with Daisy air rifles, the single-shot spring piston can deliver a BB at 250 to 300 feet per second.
The pneumatic form can deliver a velocity of 300 to 700 feet per second, and the CO2 gun can deliver a missile of 400 feet per second. Keep in mind that a pellet velocity of only 150 feet per second is necessary to penetrate human skin and 200 feet per second to penetrate bone.
With that being said, I have seen BB injuries ranging from simple skin penetration with a BB lodging in the periorbital area, to BBs causing double perforation of the globe, to BBs with double perforations going across the mid-face ending up in the opposite parietal lobe of the brain. The sequela of these injuries can be vision-threatening.
Every attempt should be made to obtain an accurate history with emphasis on the type and mechanism of injury. The examination is complemented by orbital ultrasound and computed tomography scans of the head and orbit. Ultrasound can aid in detecting posterior ocular lesions, such as a foreign body and retinal detachment that may be obscured by anterior segment disruption and hyphema. Axial and coronal CT scanning is crucial in evaluating gunshot wounds.
It provides visualization of soft tissue, bone structures and foreign bodies. In the initial acute stages, MRI is not as useful as CT scans because it does not show bony abnormalities, and magnetic foreign bodies may cause damage to the brain and intraocular structures.
BB extraction is dependent upon its location and potential for damage. Because the BBs are made of steel, they are not very reactive and, in most instances, should be left alone unless intraocular. Looking for a 4.5-mm sphere in the orbit with little potential for damage is difficult and may lead to unnecessary complications.
Disclosure: Levine has no relevant financial disclosures.