Keyhole fracture of the skull.

The authors present the case of a soldier wounded in Iraq with a gunshot wound to the skull exhibiting a characteristic keyhole fracture pattern on CT scan. Tangential gunshot wounds to the skull were termed “keyhole fractures” by Spitz in 1980 and the mechanics involved in the creation of the defect were later described by Dixon in 1982 (1,2). Keyhole fractures exhibit entrance and exit wound defects resulting from a projectile striking the cranium tangentially. The projectile’s initial impact creates a circular entrance defect as the bullet strikes the outer table of bone and a secondary fracture is created by bone fragments propagated from the initial point of impact (2). External examination of the wound can therefore be confusing, manifesting signs of both entrance and exit type trauma (3). In triaging such wounds, it is useful for the examiner to be aware of the mechanics behind tangential gunshot wounds to quickly classify the type of injury and the associated trauma incurred by the patient. CT imaging is of particular importance in the medical work up of tangential gunshot wounds as it can show the keyhole fracture of the cranium as well as the lie of potential bone fragments within the calvarium. The following report reviews the presentation, role of imaging studies, and pathophysiology for keyhole fractures of the cranium.