Orbitocranial Penetration of Ball Bearing Gun Trauma: A Prospective Human Cadaveric Study.

ABSTRACT

Objective We completed a prospective human cadaveric study to determine the ability of a ball bearing (BB) pellet to penetrate the orbit and/or surrounding structures. Methods A single trained sergeant officer discharged an alloy steel air rifle to eight cadaver orbits from four adult human cadaver heads. Five BB pellets each were aimed at three locations (caruncle, upper eyelid, or lower eyelid) at 10 cm and 1 m, and then less specifically, at the orbital region for 3- and 5-m distances. Computed tomography (CT) of the cadaver heads was performed. Final locations of BB pellets are divided into three categories intracranial, surrounding orbital structures including the pterygopalatine fossa and infratemporal fossa, and orbit. Results Of 40 BB pellets, 37 penetrated soft tissue and were visualized on CT 19 (51%) rested in the intracranial space, 17 (46%) in surrounding orbital structures, and 1 (3%) within the orbit. The deepest position of a pellet was in the parietal lobe, and most superficial location anterior to the frontal bone. Pellets discharged from 1 m were more likely to rest in the intracranial space compared with those from 10 cm ( p < 0.001), 3 m ( p = 0.011), and 5 m ( p = 0.004). The distance of discharge was associated with final pellet location ( p = 0.001). Conclusion BB guns should be considered dangerous and potentially deadly when aimed at the orbit. Although the thick calvarium can protect the intracranial space from BB penetration, the orbit may be a vulnerable entry point with relatively low resistance, allowing penetration of the intracranial and periorbital spaces.