Management of Frontal Sinus Fractures
Paul J. Donald
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:
“Through and through”
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.
The patient with an undisplaced fracture of the anterior wall fracture will probably have no abnormal physical findings other than edema of the forehead over the site of trauma. Care must be taken to not mistake a subgaleal hematoma for a displaced fracture. To palpation, the subgaleal hematoma may feel like a displaced fracture, but a CT scan of the skull will reveal no evidence of bony displacement.
An isolated fracture of the posterior wall is usually accompanied by a companion fracture of the anterior wall. The only situation when an isolated fracture of the posterior wall is seen is when it is part of an extensive adjacent skull fracture especially when it is displaced. A nondisplaced fracture of the posterior wall of the sinus cannot clinically be differentiated from a displaced fracture. A nondisplaced fracture without a dural tear is not only difficult to detect clinically but even on a CT scan especially if it is thick cut. When such a fracture lacerates the underlying dura, it is often accompanied by CSF rhinorrhea, or in the case of an overlying laceration, leakage through the lacerated skin.
Fractures of the nasofrontal duct are difficult to diagnose clinically but may be suspected by nasal endoscopy. The clinician should have a high index of suspicion in cases of an accompanying Le Fort III fracture or a naso-fronto-orbital fracture especially when it is displaced. The through-and-through fracture is usually very obvious on clinical examination. The anterior wall is usually fragmented. Blood, CSF, and even brain may be seen oozing onto the forehead. There is common association with polytrauma especially in a motor vehicle accident or in a combat or terrorist situation.
Undisplaced fractures of the anterior wall usually do not require repair. The vast majority of depressed fractures should have an open reduction and internal fixation to avoid a depression in the forehead, as well as the possibility of entrapped mucosa forming a mucocele later on. The biggest dilemma surrounds the management of a nondisplaced fracture of the posterior wall. The problem is to be certain that there is no entrapment of sinus mucosa in the fracture line that has the serious potential of developing a mucocele which will expand into the anterior cranial fossa. Modern fine cut CT scanning has reduced the chance of misinterpretation but such patients require close follow-up.
The most difficult fracture of the frontal sinus to detect is that of the nasofrontal duct. Except in circumstances mentioned above, a degree of watchful waiting is the most conservative approach. If there is radiographic evidence of retained secretions within the sinus cavity, the sinus should be further investigated.
The only contraindication to surgery in a patient with a through-and-through fracture of the sinus would be fragility of the patient’s condition. The Otolaryngologist must strongly persuade the Neurologic surgeon not to pack the sinus cavity with methacrylate or bone wax.
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.
Fractures of the Anterior Wall
Undisplaced isolated fractures of the anterior wall generally do not require treatment. Periodic observation with a yearly CT scan for several years is usually sufficient follow-up. A caveat regarding physical examination of undisplaced fractures is that a fresh injury to the frontal area may feel through the skin as if there is an underlying sharp fracture line. This sensation can be created by a subgaleal hematoma. Re-evaluating the CT scan will reveal the true nature of the fracture which is actually nondisplaced. On the other hand, a hematoma overlying a depressed fracture of the anterior wall may give the appearance of a normal contour of the forehead.
Displaced fractures must be reduced because of the residual deformity that will evolve as the overlying hematoma of the forehead resolves, but more importantly, because of the possibility of developing a mucocele in the future because of entrapment of mucosa in the fracture line.
There are three types of incisions which may be used to access the fracture: the coronal scalp incision, the so-called butterfly incision, and an extension of a forehead laceration in the case of a compound anterior wall fracture (Fig. 53.3). The coronal scalp incision is the most useful. If the patient is male and has all his hair, the incision is made about 2 or 3 cm. behind the hairline and curves forward at the widow’s peak. Xylocaine 1% with 1:100,000 epinephrine is injected along the proposed incision line and the actual incision delayed for at least 5 minutes in order to maximize the vasoconstrictive effect. Raney clips and bipolar cautery are used to ensure hemostasis.