Chapter 16. Frontal Sinus Fractures

• History of head trauma.
• Visible open fracture or fracture on computed tomography (CT) scans or plain X-rays.

The frontal sinus begins as an outgrowth of the nasal chamber in utero but does not begin to invade the vertical portion of the frontal bone until the 4th year of life. The sinus attains adult configuration at age 15 and typically reaches adult size by age 20. A variable structure, the frontal sinuses are typically asymmetric and may be unilateral (10%) or absent altogether (5%).

The anterior wall of the fully developed frontal sinus is a thick bony arch that can withstand between 800 and 2200 pounds of force. The force required to fracture this robust structure often leads to multiple injuries; therefore, a full trauma workup of all patients with frontal sinus fractures is paramount. As with all trauma patients, the airway, circulatory system, and other organ systems must be evaluated upon arrival. All patients require ophthalmologic and neurologic examination as well as radiographic and clinical examination of the cervical spine. Intracranial injury (40–50%) and other facial fractures (75–95%) are among the most commonly associated injuries in patients with frontal sinus fractures.

Motor vehicle accidents are the most common mechanism of injury for patients with frontal sinus fractures, accounting for 60–70% of all frontal sinus fractures. Assault typically requires the use of a blunt object to fracture the frontal sinus; fists alone rarely generate sufficient force. Other mechanisms of injury include industrial accidents, recreational accidents, and gunshot wounds. Young men in their third decade of life are most at risk for frontal sinus fracture. In one study, 30% of patients with frontal sinus fractures had blood alcohol levels over the legal limit or positive urine toxicology screens.

The anterior wall of the frontal sinus is significantly thicker than the posterior wall. Injuries that provide enough force to fracture the anterior wall of the frontal sinus often have enough force to fracture the posterior wall as well.

The use of seatbelts and airbags for passengers and drivers can decrease the incidence of severe head trauma and frontal sinus fractures. Patients in automobile accidents in which airbags are deployed have a significant decrease in the number of facial fractures. Estimates are that only 15% of young patients with frontal sinus fractures resulting from automobile accidents were wearing a seatbelt; less than 10% of patients with frontal sinus fractures from motorcycle accidents were wearing a helmet. The use of helmets with motorcycles, with bicycles, at appropriate sporting events, and in industrial situations also can protect the frontal sinuses.

Symptoms and Signs

Most patients lose consciousness with the force required to sustain a frontal sinus fracture; estimates are that 25% of patients remain conscious throughout the injury, 50% regain consciousness within the first 4 hours after injury, and the final fourth develop prolonged unconsciousness.

Patients who are conscious at the time of the evaluation typically report frontal pain. Forehead lacerations occur in approximately 80% of frontal sinus fractures. Other less common signs on physical examination include the following: frontal numbness; palpable step-offs or crepitus; cerebrospinal fluid (CSF) leak; exposed bone; exposed brain; and ocular abnormalities, including diplopia, ophthalmoplegia, and decreased visual acuity. Between 5% and 10% of patients have no significant physical findings on examination.

Associated injuries are the rule with frontal sinus fractures. Other facial fractures occur in up to 95% of patients; bones of the orbit and paranasal sinuses are the most commonly involved. Intracranial injuries are seen in approximately 50% of patients; of these types of injuries, frontal contusions are the most common.

Imaging Studies

CT Scans

CT scanning is the imaging examination of choice for the evaluation of frontal sinus fractures. Clinicians looking for intracranial pathology after head trauma order CT scans of the head and often discover fractures.

When evaluating the extent of injury and determining the operative plan for frontal sinus fractures, thin-cut axial and coronal facial CT scans are preferable to thicker-cut 5–10 mm head CT scans. Presently, fine-cut axial CT scans with coronal and saggital reconstruction are typically used for the evaluation of frontal sinus fractures. Slice thickness of 0.625 mm is ideal, although a thickness of up to 2 mm is typically adequate. Direct coronal views are less amenable to axial and saggital reconstruction and are often contraindicated in patients with frontal sinus fracture related to possible cervical spine injury and issues related to other associated injuries. Soft tissue windows should be used to evaluate intracranial and orbital injuries, which are often seen in patients with frontal sinus trauma. Many patients with associated injuries do not tolerate direct coronal images. Figures 16–1 and 16–2 are axial images of a patient with a depressed anterior table frontal sinus fracture and frontonasal recess injury, respectively.

X-Rays

The role of plain X-ray films in the evaluation of frontal sinus fractures is limited. In patients with nonoperative fractures and fluid in their frontal sinuses, serial Caldwell views may be used to monitor resolution of the fluid, insuring patency of the frontonasal recess.

Frontal sinus fractures should be distinguished from both simple forehead contusions and lacerations. Frontal bone fractures without the involvement of the frontal sinus may be mistaken for frontal sinus fractures. CT scans distinguish between these possibilities with ease.

Determining the extent of a fracture is more difficult than determining whether a frontal sinus fracture is present. Involvement of both the posterior table of the frontal sinus and the frontonasal recess is critical in determining the treatment of the fracture. Anterior table fractures are often easily identified on axial CT scans; however, because of the thin nature of the posterior table, nondisplaced posterior table fractures can be less obvious. A high index of suspicion for posterior table fractures is necessary in all patients. Pneumocephalus on the CT scan may provide a clue that the posterior table has been violated, but pneumocephalus also may come from fractures of the ethmoid bones or other aerated regions of the skull.

In patients with frontal sinus fractures, the frontonasal recess is the most difficult area to evaluate. When evaluating a frontal sinus fracture, it is important to assess the future function of the frontonasal recess. In the surgeon's judgment, if disruption of frontal sinus drainage is likely, then obliteration or cranialization (ie, removal of the posterior table and mucosa of the frontal sinus) of the frontal sinus should be strongly considered. Serial imaging studies may be considered in select patients in whom reliable follow-up is likely. Certain fracture patterns can be helpful in predicting frontonasal recess damage. In isolated anterior wall fractures, involvement of the frontonasal recess is rare. Patients with anterior wall fractures and associated supraorbital rim or nasoethmoid complex fractures have associated frontonasal recess injury in 70–90% of cases. Combined anterior and posterior wall fractures are also commonly associated with injury to the frontonasal recess.

There are many complications of frontal sinus fractures. More severe complications include mucoceles, severe persistent pain, and infectious intracranial complications. Such complications are uncommon, with a reported rate of 6% for meningitis and mucocele formation and 1% for severe pain and brain abscess.

Minor complications are relatively common. Wound infections, CSF leaks, numbness over the forehead area, and mild deformity are each found in approximately 10–20% of patients. Chronic sinusitis, mild chronic pain, and diplopia (ie, double vision) are significantly less common.

Well-known complications of frontal sinus fractures include (1) mucoceles and mucopyoceles; (2) intracranial complications such as meningitis, brain abscess, and CSF leak; and (3) other complications such as chronic infection and osteomyelitis. All of these complications, particularly mucoceles, may not manifest until years or decades after the original injury. With the evaluation of the extent of the injury and appropriate treatment, complications from frontal sinus fractures can be limited.

Mucoceles and Mucopyoceles

Mucoceles and mucopyoceles are well-known complications that typically appear years after the original injury. Because of their severity, these complications usually mandate surgical intervention.

Mucoceles are expansile, benign, but locally destructive lesions that occur when entrapped or segregated mucosa secretes mucus into a confined space, causing progressive expansion. Frontal sinus mucosa is distinct from normal pseudostratified ciliated respiratory epithelium both histologically and pathologically. Frontal sinus mucosa tends to have a flatter, more cuboidal epithelium with a greater propensity for mucocele formation. Conditions that tend to result in mucocele formation include frontonasal recess obstruction and mucosa entrapment, both commonly associated with frontal sinus fractures.

The foramina of Breschet are venous drainage channels located in the posterior wall of the frontal sinus. These foramina are significant not only because they provide a route for intracranial spread of infection but also because they act as sites of mucosal invagination in the posterior wall of the sinus. Failing to completely remove mucosa in an obliterated sinus predisposes the development of mucoceles. Mucoceles tend to follow an insidious course with significant bony destruction and potential erosion into the intracranial, intraorbital, or subcutaneous space.

The entrapped, static secretions within mucoceles may become infected, resulting in a mucopyocele. Mucopyoceles tend to follow a more aggressive course than mucoceles. Expansile, infectious masses, mucopyoceles carry significant risks of intraorbital infectious complications; they also may erode directly into the intracranial space.

Intracranial Complications

Meningitis and brain abscesses may occur as early or late sequelae of frontal sinus fractures. Frontal sinus fractures are often compound, dirty wounds at the time of injury, with bits of glass and dirt within the wound. This early contamination combined with the frequent association of posterior table fractures and even dural tears provides a direct route for bacterial entry to the intracranial space, which results in meningitis, a brain abscess, or both. Late intracranial infections are typically associated with mucopyoceles.

Traumatic CSF leaks are another form of intracranial complications. They have been noted to seal spontaneously in 80–95% of cases; however, these data may be skewed by a high percentage of temporal bone fractures. It is estimated that in patients with a traumatic CSF leak present for more than 24 hours, approximately 53% resolved spontaneously within an average of 5 days. Those leaks that go unrecognized or are not adequately repaired may result in delayed intracranial infections.

Other Complications

Chronic infection and osteomyelitis may occur after frontal sinus fracture. This can result in the development of a frontocutaneous fistula and chronic drainage as well as the extrusion of hardware used during frontal sinus repair. Chronic frontal sinus pain and the sensation of frontal sinus fullness may be present after both frontal sinus fracture and obliteration. Severe or unrelenting pain may be a sign of mucocele development or infectious complication and should be evaluated thoroughly. Cosmetic forehead deformities may result after inadequate reduction of anterior table fractures or the loss of anterior table bone. Mucoceles, mucopyoceles, osteomyelitis, or hardware extrusion can also result in cosmetic deformities.

The treatment of frontal sinus fractures depends on the extent of the fracture. Fractures of the frontonasal recess and the posterior table of the frontal sinus often require operative intervention. Displaced fractures typically require open reduction. The primary goals of treatment in frontal sinus fractures include preventing complications and restoring normal forehead contour.

Surgical Measures

Surgical developments within the last few decades have reduced marked cosmetic deformities and a high incidence of long-term complications. Modern techniques of evaluation and treatment allow better triage of patients with frontal sinus fractures to surgical intervention or observation. Fine-cut CT scanning as well as office and intraoperative endoscopy have allowed surgeons to improve patient selection for ablative surgery. In the past, the ablative procedures of a frontal osteoplastic flap and the cranialization procedure were the two primary procedures used to repair complex frontal sinus fractures. Fractures thought in the past to require these interventions, particularly posterior table fractures, have more recently been shown in case series and animal models to be amenable to more conservative treatment. The choice of when to operate and which procedure to perform depends on the extent of the fracture and functional evaluation of the frontonasal recess.

In addition to improved methods of patient selection, more recent advances in instrumentation and technique have also allowed less invasive methods including endoscopy to be used to repair and/or camouflage fractures. Endoscopic techniques are performed through small incisions behind the hairline similar to the approach used for an endoscopic brow lift.

Open Reduction and Internal Fixation

This method exposes fractured bone and replaces the fragments as close to their original configuration as possible. Fixation is typically accomplished with a combination of plates and screws contoured to the bony fragments. Approaches principally include direct approaches through lacerations, a mid brow incision, and the coronal approach (Figures 16–3 and 16–4).

The Osteoplastic Flap

The concept of removing the frontal sinus as a functioning unit was introduced in 1958 by Goodale and Montgomery with the osteoplastic flap. This flap or hinged opening of the frontal sinus is created through either a midforehead or a coronal incision and sinus obliteration; this approach may also be used through an existing forehead laceration. The procedure, which remains one of the principal means for treating frontal sinus fractures today, involves raising a subperiosteal flap from a coronal or midforehead incision down to the superior border of the frontal sinus. The anterior table of the frontal sinus is then opened at its superior and lateral margins, creating an inferiorly based bone flap. All mucosa is then stripped from the sinus, and all the bony walls of the sinus are burred down with a drill to ensure complete mucosal removal. The frontonasal recess mucosa is stripped or turned down into the ostium, and the ostium is obliterated using a muscle or fascia plug. The sinus is then obliterated, most commonly using a free fat graft. Finally, the anterior wall of the frontal sinus and the coronal or midforehead flap is replaced.

The Cranialization Procedure

In the cranialization procedure, the posterior wall of the frontal sinus is removed and the frontal dura is allowed to rest against the anterior table of the frontal sinus. This procedure also involves complete stripping of the mucosa, burring any mucosal remnants from the remaining anterior sinus wall, and plugging the frontonasal recess.

Endoscopic Repair

Using endoscopic techniques, incisions can be made smaller and morbidity from extensive dissection minimized. At this point, endoscopic techniques are used to repair and/or camouflage frontal sinus fractures involving the anterior table only, although technique development is ongoing. Small incisions behind the hairline are used to reduce and fixate fractures and camouflage contour defects through onlay grafts and other techniques for improved cosmesis. Endoscopic transnasal reduction of anterior table frontal sinus fracture has also been reported. The endoscope can be very useful, however, in examining the frontonasal recess and other areas during surgery.

Surgical Grafts

There has been significant debate over which material is best for obliterating the frontal sinus. One option is to remove all mucosa, plug the frontonasal recess, and allow ingrowth of fibrous tissue without obliteration. Other options involve the use of various grafts.

Autologous Fat Grafts

Free-fat grafts have been both studied and used most extensively. Overall autologous fat provides a safe obliterative material with few infectious complications. Over time fat tends to be reabsorbed and replaced with fibrous material. Serial MRI scans in patients with fat-obliterated frontal sinuses show the median half-life of the obliterated adipose tissue to be 15.4 months. In addition, the incidence of seroma in fat harvests is approximately 5%.

Other Autologous Tissue Grafts

Other autologous tissues for obliteration include cancellous bone, muscle, and pericranial flaps. Autologous grafts typically involve some donor site morbidity, such as pain, infection, or the formation of sarcomas, hematomas, or both. Pericranial flaps with an inferior or lateral base offer a living tissue option for both obliteration and recreation of the anterior table with minimal donor site morbidity.

Grafts of Synthetic Materials

One difficult situation in which synthetic materials may play a role is in fractures with a loss or a severe comminution of the anterior table. In these scenarios, bone grafts (iliac, rib, or split calvarial) or methyl methacrylate have been used to recreate the anterior table. Titanium mesh offers a synthetic alternative for severely comminuted fractures, but its use is limited in cases with significant loss of anterior table bone. Hydroxyapatite cement is another synthetic material that has been used both to obliterate the sinus and recreate the anterior table but experience is limited. Reoperation on patients obliterated with hydroxyapatite and some other synthetic materials is challenging.

Location-Related Measures

Anterior Table Fractures and Frontonasal Recess Injuries

To treat fractures of the anterior wall appropriately, a couple of key issues need to be resolved. The first is the degree of the displacement of the fracture; this question can be answered easily with a combination of physical exam and CT scan. If a displaced fracture is present, exploration of the fracture with open reduction and internal fixation is required (Figure 16–1).

The second key issue in treating fractures of the anterior wall is whether there is significant injury to the frontonasal recess. Figure 16–2 depicts a CT scan in a patient who has a frontonasal recess injury. The frontonasal recess is more difficult to evaluate accurately on a CT scan because the functional capability of the frontal sinus drainage pathway is not clearly elucidated on CT. A 70–90% rate of frontonasal recess injury has been reported for patients who have associated fractures of the floor of the frontal sinus, the nasoethmoid complex, or the supraorbital rim. It is thus reasonable to surgically evaluate the frontonasal recess in such patients.

Traditional management of fractures involving the frontonasal recess is operative exploration and either obliteration or cranialization if injury to the frontonasal recess is noted intraoperatively. However, some studies suggest that fractures with frontonasal recess involvement do not always require obliteration or cranialization. Some physicians have managed these patients expectantly, following this approach with serial CT scans. Patients who failed to re-aerate their sinuses were treated with endoscopic frontal sinus procedures; in limited trials, favorable results were obtained. The trend in modern management of these fractures in patients for whom follow-up is feasible is toward more expectant management of frontonasal recess injury and follow-up CT scanning to assess functional patency.

For unilateral frontonasal recess injuries in which the contralateral duct has been demonstrated to work, some clinicians advocate the Lothrop procedure: removal of the intersinus septum and the use of mucosal flaps to allow drainage through the contralateral frontal sinus. This procedure can be performed endoscopically.

Posterior Table Fractures

Fractures of the posterior table may require surgical intervention. This is an area where treatment recommendations are in evolution secondary to improved methods of imaging and improved understanding of the role of the frontonasal recess in mucocele formation.

In general, posterior table fractures are suspicious for dural disruption and CSF leak. Dural tears with persistent CSF leak should be repaired in consultation with a neurosurgeon. In the absence of persistent CSF leak, some clinicians advocate the use of serial CT scanning and close follow-up of nondisplaced or minimally displaced posterior table fractures. The treatment of displaced posterior table fractures is controversial and may require obliteration or cranialization based on the surgeon's judgment. These fractures have a high incidence of frontonasal recess injury and, untreated, have a theoretical risk for mucocele formation. The modern trend, however, is toward expectant management and serial CT scanning in reliable patients who have posterior table injuries with good aeration of the sinuses.

Comminuted and displaced posterior table fractures are best treated with cranialization. “Through and through” injuries involve significant injury to the skin, anterior table, posterior table, and dura. These injuries can often be diagnosed by viewing the brain through the wound and are best managed with cranialization if sufficient bone remains to recreate the anterior table. In cases of severe anterior and posterior table bone loss, ablation may be the only viable alternative.

Frontal sinus fractures in the pediatric population are more commonly associated with orbital fractures and major intracranial injury such as intraparenchymal hemorrhage and CSF leak. Patients with intracranial injury tend to be younger than those with no intracranial injury. The cribriform plate is involved to a greater degree as a site of CSF leak than in adults, and craniotomy is commonly needed for CSF leak repair.

Short-Term Prognosis

The immediate prognosis for patients with frontal sinus fractures is mostly dependent on the presence and severity of the associated injuries, particularly intracranial injuries. Patients with “through and through” frontal sinus fractures have a short-term mortality rate of approximately 50% at the scene or in transport. Another 25% die in the early postoperative period.

Long-Term Prognosis

The long-term prognosis for patients with frontal sinus fractures has been difficult to assess. With the significant possibility of delayed complications, long-term follow-up is required to adequately evaluate the prognosis for patients with frontal sinus fractures. These patients, however, tend to be noncompliant, making long-term follow-up problematic. Because of this dilemma, the prevalence of long-term complications is likely understated in the literature.