Clothing increases the risk of indirect ballistic fractures.

BACKGROUND: Current literature has shown the mechanism of how indirect fractures occur but has not determined what factors increase the risks of such fractures. The objective of this study is thus to determine the effect of clothing and soft tissue thickness on the risk of indirect fracture formation. METHODS: Twenty-five fresh red deer femora embedded in ballistic gelatine were shot with varying distances off their medial cortex with a 5.56 × 45 mm North Atlantic Treaty Organization (NATO) bullet while being filmed with a slow-motion video. We compared the effect of two different gelatine depths and the effect of denim cloth laid onto the impact surface of the moulds. RESULTS: Bullet passage in thinner moulds failed to cause fracture because the bullet exited the mould before a large expanding temporary cavity was produced. Clothing dramatically altered the size and depth of the expanding cavity, as well as increased lateral pressures, resulting in more severe fractures with greater bullet distances from the bone that can cause fracture. CONCLUSIONS: Clothing increases the risk of indirect fracture and results in larger, more superficial temporary cavities, with greater lateral pressures than are seen in unclothed specimens, resulting in more comminuted fractures. Greater tissue depth affords the 5.56 × 45 mm NATO a chance to yaw and thus develop an enlarging temporary cavity that is sufficient to cause fracture.

Remote ballistic fractures in a gelatine model--aetiology and surgical implications.

BACKGROUND: Remote ballistic femoral fractures are rare fractures reported in the literature but still debated as to their existence and, indeed, their treatment. This study aimed to prove their existence, understand how they occur and determine which ammunition provides the greatest threat. In addition, fracture patterns, soft tissue disruption and contamination were assessed to aid in treatment planning. METHOD: We filmed 42 deer femora embedded in ballistic gelatine and shot with four different military (5.56 × 45 mm, 7.62 × 39 mm) and civilian (9 × 19 mm, .44 in.) bullets, at varying distances off the bone (0-10 cm). RESULTS: Two remote ballistic fractures occurred, both with .44 in. hollow-point bullets shot 3 cm off the bone. These fractures occurred when the leading edge of the expanding temporary cavity impacted the femur's supracondylar region, producing a wedge-shaped fracture with an undisplaced limb, deceivingly giving the appearance of a spiral fracture. No communication was seen between the fracture and permanent cavity, despite the temporary cavity encasing the fracture and stripping periosteum from its base. CONCLUSION: These fractures occur with civilian ammunition, but cannot prove their existence with military rounds. They result from the expanding temporary cavity affecting the weakest part of the bone, creating a potentially contaminated wedge-shaped fracture, important for surgeons considering operative intervention.