BB and Pellet Gun-Related Injuries

Mark R. Levine, MD · Amarpreet Singh, MD · Toni Meyers, MD

Introduction

Ball bearing (BB) and pellet gun-related injuries represent an important public health concern in the United States. Most of these injuries occur in children and teenagers 19 years of age or younger. In all incidents of pellet gun-related injuries, adults were present only 11% of the time.¹ BB and pellet gun-related injury rates increased from 3 years old, peaked at 13 years of age, and declined thereafter. The BB and pellet gun-related injury trend for those aged 19 years and younger showed an increase from the late 1980s until the early 1990s and then declined until 1999. The injury rates were 24.0 in 1988, 32.8 in 1992, and 18.3 in 1999 (per 100,000). This is based on the National Electronic Injury Surveillance System (NEISS) operated by the U.S.

An estimated 3.2 million BB/pellet guns are sold in the United States each year. Many parents under the delusion that BB guns are harmless toys, continue purchasing these guns without teaching their children gun safety. In the United States, an estimated six deaths per year are related to the misuse of BB guns or pellet guns. These deaths, as well as other injuries, are usually due to high velocity BB guns of more than 350 feet per second (fps) (www.airgun.org).

Case Report

A 12-year-old boy presented to the emergency department with a BB gun injury to the left eye at close range by one of his friends. When the BB gun accidentally fired, the BB double perforated the boy's left globe, entering the cornea at the 5 o'clock position at the limbus and exiting posteriorly and superiorly (Slide 1, Slide 2). Vision in the injured eye was light perception, IOP was 6 mm Hg by applanation, and a total hyphema was present. A skull radiograph (with computed tomography [CT] confirmation) showed that the BB lodged in the right parietal lobe of the brain after having traversed the midface (Slide 3, Slide 4, and Slide 5). Primary closure of the corneo-scleral laceration and posterior scleral laceration was undertaken followed by a vitrectomy within 2 weeks of the injury. The eye became phthisical with an associated secondary ptosis (Slide 6). The BB was left in the parietal lobe of the brain and no antiseizure medications were administered, and the patient remained seizure-free.

Discussion

The three propulsion systems used in BB and pellet guns are spring piston, manual pump compression, and CO2 stored in disposable cartridges. The spring piston air gun is powered by the compression of a mainspring after being manually cocked. They have a muzzle velocity of 250 to 300 fps. Manual compression guns can have a muzzle velocity of up to 900 fps because the user can increase the level of pressurized air through multiple pumps. Pressurized CO2 cartridge guns generally have a muzzle velocity of 400 to 450 fps, although some newer models have velocities of up to 930 fps.³

Studies have shown that, over a short distance, many of these guns can shoot projectiles at the same speed as conventional firearms. Although pistols have muzzle velocities rivaling BB and pellet guns (.45 at 860 fps, .38 revolver at 750 fps, .38 automatic at 970 fps, and .32 at 800 fps), BBs and pellets lose their velocity at faster rates than conventional firearms. Therefore, the risk of injury decreases quickly as the distance between the gun muzzle and point of impact increases.⁴

Velocity is an important factor in terms of tissue injury after impact. You will recall the following equations from physics:

F = MA
A = (V²)/2

The most important factor in determining the force of injury is the velocity. The higher the velocity of the projectile, the greater the tissue disruption at impact due to kinetic energy. It takes an impact velocity of 132 fps to penetrate the human eye, 290 fps to penetrate skin, and 331 fps for complete passage through the skin and into soft tissues.

Although information regarding ammunition is not always available when assessing a traumatic patient, it is important to consider the possibilities. Lead BBs were popular in the past but have fallen out of favor. Now, BBs are typically composed of steel (96% to 98% iron composition). To protect the steel from erosion, the BBs are either chemically coated with copper or plated in zinc with a lacquer overlay. Although the copper and zinc comprise less than 1% of the total structure, they are of a pure composition. Paint guns and air soft guns (maximum velocity of approximately 280 fps) use 6-mm paint and plastic BBs, respectively. These alternatives have gained considerable popularity over the past several decades.

Air gun owners can also choose from a variety of pellets, which are available in four shapes: domed, pointed, wadcutter, and hollow-point (Slide 7). The domed variety is an all-around pellet designed to deflect wind due to its aerodynamic, rounded surface. The pointed type tends to hold its velocity longer and is used for long-range penetration, whereas the wadcutter has a limited penetration due to the flat head design and is used mainly in competition. The hollow point has an expansive nature and, on impact, causes more extensive contusive injuries secondary to shock waves.

Evaluation and Management

The location and extent of injury directly correlates with visual prognosis. It is well documented that the more posterior the injury, the worse is the prognosis for visual rehabilitation.^5,6Additionally, penetrating injuries overall are associated with lower visual potential than non-penetrating injuries.

Management of patients depends on the location of the projectile. Ancillary radiographic studies such as plain films and CT scans are critical first steps in locating and pinpointing the foreign body. In cases where the projectile is readily accessible, surgery should be considered. If the projectile is located in the posterior portion of the orbit and is inaccessible, then it can often be left in place. However, surgical removal should be considered in the setting of marked orbital inflammation, infection, or CT evidence of optic nerve impingement with associated optic neuropathy.

One study found no late complications from retained intraorbital foreign bodies in 36 of 38 cases (95%) when the globe remained intact.⁷ However, when the foreign body is retained intraocularly, surgical removal should proceed in an expedited manner to decrease the risk of siderosis as well as chronic chalcosis in the case of a copper-coated BB. A thorough neurological examination is also warranted because air guns can penetrate the orbital walls to enter brain tissue.

Although penetrating and perforating injuries are associated with lower visual potential, the advances in surgical technique have improved overall outcomes. A study completed in 1984 reported 22 penetrating injuries, 19 of which were enucleated. The remaining three patients had a final visual acuity of less than 5/200.⁸ In contrast, another study published in 1997 reported final visual acuity of 5/200 or better in 83% of postsurgical patients with perforating injuries by BB guns.⁹ These improvements in outcome correlated with the aggressive surgical management using modern vitrectomy techniques and give hope to those with serious eye injuries.

In summary, BB and pellet gun injuries are varied and sometimes fatal. The injury rates have declined over the past 10 years, coinciding with increased prevention efforts aimed at reducing injuries to children. By providing adequate supervision and appropriate eyewear, the downward trend will continue during the coming years.

References

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9. Pulido JS, Gupta S, Folk JC, Ossoiny KC. Perforating BB gun injuries of the globe. Ophthalmic Surg Lasers. 1997;28:625-632.