Imaging description

Blunt trauma to the orbit often results in an orbital wall fracture. The predominant fracture patterns are different between adults and pediatric patients. In adults, the medial orbital wall and the orbital floor are the most common sites of fracture (Figure 18.1). In children, especially those less than seven years of age, the most common orbital fracture involves the orbital roof. This is explained by the prominence of the frontal bone relative to the size of the face in children. Also, the frontal sinus does not develop until the age of seven years; thus, there is lack of the normal cushioning effect from the sinus, and frontal bone fractures tend to extend into the orbital roof [1].

A trapdoor fracture may occur in children and young adults (Figure 18.2). In this type of injury a linear orbital floor fracture results in inferior bony displacement. However, due to the elasticity of the floor, the bone fragment swings back to the normal position in a hinge-like manner. These types of fractures may be subtle, but they are associated with a high rate of tissue entrapment [2]. If there is any evidence of orbital fat inferior to the orbital floor, a fracture must be presumed present. Another useful finding is hemorrhage within the maxillary sinus, which is often but not always associated with an orbital floor fracture (Figure 18.3).