Fractures of the frontal sinus have become less common due to the introduction of the seat belt in modern automobiles. The frontal sinus is contained within the frontal bone and is particularly vulnerable to violent trauma due to its position in the anteroinferior skull. Fortunately, there are a number of anatomical features that make it the strongest structure in the facial skeleton. The thick bone of the anterior skull coupled with its arch configuration is also reinforced by a series of septations that act as trusses rendering it highly resistant to fracture. It takes about 800 to 1,600 ft-lb of pressure to fracture the anterior wall of the frontal sinus compared to 550 to 900 ft-lb to fracture the mentum of the mandible and 200 to 650 ft-lb to fracture the body of the zygoma. In contrast, the posterior wall and floor of the sinus are thin and fragile. The posterior wall forms the anterior wall of the anterior cranial fossa. The floor is in common with the roof of the orbit.

Each frontal sinus has a funnel-shaped duct located in the anteromedial aspect of floor of the sinus adjacent to the intersinus septum located vertically in the midline of the sinus. The mucosa of the sinus has a characteristic and unique response to injury. Damaged mucosa tends to form cysts which as they expand fill the sinus cavity. These frontal sinus mucoceles erode bone and can become secondarily infected forming a mucopyocoele.

Fractures of the frontal sinus can be classified in a number of ways. Initially, they are classified according to the wall or walls involved:

They are also classified according to type:

The utility of this classification system is that each specific type of fracture demands a specific treatment, and in so many instances, the fractures will be of multiple walls and multiple types; therefore, the treatment plan will need to incorporate all of the appropriate modalities that are specific to each site and type of fracture.

The two classification types requiring further explanation are the “corner fracture” and the “through-and-through” fracture. The corner fracture (Fig. 53.1) is basically a skull fracture that goes through the lateral extremity of the frontal sinus usually including the anterior and posterior walls and the floor. It is undisplaced and does not require operative treatment. The “through-and-through fracture” is the most severe of all the fractures and usually accompanies a more severe type of skull fracture that is compound and comminuted. The injury includes a compound, comminuted fracture of the anterior and posterior walls of the frontal sinus. The dura is torn and the underlying brain lacerated and contused (Fig. 53.2). Most patients with through-and-through fractures are victims of polytrauma and 50% die at the scene of the trauma or in the hospital.

The force required to fracture the frontal sinus is considerable such that a history of violent trauma followed by a variable period of unconsciousness is generally the rule. The most catastrophic of these injuries, a through-and-through type of fracture, is often first encountered when the Otolaryngologist enters the operating room following a call from a Neurosurgeon who has the patient draped on the table, has stopped the intracranial bleeding, patched a dural defect, and is puzzled about how to manage the wide open frontal sinus.

Most of the fracture types will be found in patients who have recovered consciousness and commonly complain of severe frontal headache. There may be numbness over the forehead if the injury to the branches of the supraorbital nerve that supplies the sinus periosteum and mucosa occurs. The patient with fractures of the anterior wall may complain of a depression or a swelling in the forehead. The swelling could be a hematoma masking an underlying depressed fracture.

Epistaxis may occur, and in fractures of the posterior wall if there is a dural tear, the drainage from the nose may be a mixture of CSF (cerebrospinal fluid) and blood. A halo sign when a drop of fluid from the nose is captured on a towel and the halo surrounding the clot is wider than the width of the clot will denote a CSF leak.

Prior to operative treatment, the patient must be stabilized and cleared by Neurological Surgery and, when relevant, Ophthalmology.

The through-and-through type is the only fracture that requires emergency surgery. There is usually bleeding from the brain and a CSF leak. A fine cut CT scan will delineate the type of fracture and the extent of displacement of the fragments for a final diagnosis.

The most difficult fracture of all to delineate is the fracture of the nasofrontal duct. Even a fine cut CT scan may not reveal this fracture. The sagittal view is the best to define this injury. If after a 2- or 3-week waiting period and repeating the scan to see if the sinus is still opacified by fluid, a functional test may be done to detect a possible fracture. A trephine is drilled in the medial aspect of the roof of the orbit lateral to the trochlea. A cannula is placed through the opening, and the fluid in the sinus is suctioned away through the trephination. The sinus is then irrigated with a mixture of saline and cocaine or epinephrine. Methylene blue is placed in the sinus cavity, the patient is placed in a sitting position, and a nasal endoscope is inserted into the nasal cavity to see if the dye appears in the middle meatus. Alternatively, radiopaque dye can be introduced into the sinus and a plain radiograph made to visualize the course of the duct and any obstruction. Another way to assess patency is to visualize the duct from the frontal sinus cavity by passing an angled telescope through the trephination. This unfortunately only reveals the status of the internal meatus of the duct. More information can be gleaned by adding an endoscopic examination of the middle meatus.

One of the problems encountered when an osteoplastic flap procedure is required is predicting the size and shape of the sinus. A 5-foot Caldwell view of the sinuses taken in the AP projection will be of great help in predicting the outline of the frontal sinus. Many radiology technicians are untrained in plain radiographs of the sinuses so this may not be an option. An alternative method is to attempt transillumination of the sinus and then map it.

If a coronal scalp flap is planned, the site of incision must be cleared of hair by braiding the hair so as to clear a path, a limited shave of the track of the planned incision is usually done. A Mayfield head rest helps with exposure and ease of access to the operative field.