A naso-orbital fracture tends to consist of a comminuted, depressed fracture involving the nasal bones, ethmoid sinuses, and medial orbital walls. It occurs when a blow of sufficient force is applied to the nasal bridge area. Such blunt trauma can cause the medial wall to develop a fracture in 1 of 2 ways. First, when the nasal bone fragments are projected backward, the thin lacrimal bone and lamina papyracea are comminuted easily. The nasal bone and frontal process of the maxilla may be displaced posteriorly into the ethmoid sinus; as a result, an in-fracturing of the medial orbital wall into the orbit occurs. Therefore, the compressive force causing nasal fractures is a very important causative factor of pure medial wall fractures.

With blowout fractures, the medial wall is fractured indirectly. When an external force is applied to the orbital cavity from an object whose diameter is larger than that of the orbit, the orbital contents are retropulsed and compressed. The consequent sudden rise in intraorbital pressure is transmitted to the walls of the orbit, which ultimately leads to fractures of the thin medial wall and/or orbital floor. Theoretically, this mechanism should lead to more fractures of the medial wall than the floor, since the medial wall is slightly thinner (0.25 mm vs 0.50 mm). However, it is known that pure blowout fractures most frequently involve the orbital floor. This may be attributed to the honeycomb structure of the numerous bony septa of the ethmoid sinuses, which support the lamina papyracea, thus allowing it to withstand the sudden rise in intraorbital hydraulic pressure better than the orbital floor.