63 Frontal Sinus and Naso-Orbito-Ethmoid Fractures

Introduction

The frontal bone is thick and very resistant to trauma. Consequently, the majority of injuries involving the frontal sinus and nasoorbitoethmoid complex are the result of high-velocity impacts such as motor vehicle accidents, assaults, and sports injuries. While the treatment of frontal sinus and naso- orbitalethmoid fractures is distinct, the anatomical proximity of these two areas warrants a combined discussion. The initial evaluation of such high-velocity injuries should focus on airway maintenance and hemodynamic stability. Once the patient is stabilized, the brain, spine, orbits, and facial skeleton should be evaluated. This often requires a team approach involving the facial plastic surgeon, neurosurgeon, and ophthalmologist. While the anatomy and mechanism of injury have been well studied, the treatment of these injuries remains controversial. Improper management can result in aesthetic deformity, chronic sinusitis, pneumocephalus, mucopyocele, meningitis, and brain abscess—all of which generally occur years to decades after the injury. The goal of treatment is avoidance of short- and longterm complications as well as the return of normal sinus function and aesthetic facial contour. While there is a trend in the literature toward minimally invasive and endoscopic approaches, there are no prospective randomized studies comparing different treatment strategies. Surgeons must remain diligent with regard to patient education and longterm followup. A treatment algorithm for frontal sinus and nasoorbitoethmoid complex injuries will be presented.

Frontal Sinus Fractures

Embryology and Anatomy

The frontal sinus is absent at birth. At approximately 1–2 years of age, the anterior ethmoid air cells invade the frontal bone to form a rudimentary cavity. By 7 years of age, the frontal sinus can be detected radiographically. The frontal sinus is adult size by approximately 15 years of age ( Fig. 63.1 ). The floor of the sinus forms the medial portion of the orbital roof. The posterior table forms a portion of the anterior cranial fossa. The anterior table forms part of the forehead, brow, and glabella ( Fig. 63.2 ). The frontal sinus is most commonly bilateral, asymmetric in shape, and divided by one or more intersinus septations. The size and shape of the adult frontal sinus are highly variable, with 10% of individuals having a unilateral sinus, 5% having a rudimentary cavity, and 4% having no sinus at all. The average dimensions are: height 30 mm, width 25 mm, depth 19 mm, and volume 10 mL. The anterior table thickness may be as great as 12 mm (average 4 mm), whereas the posterior table ranges in thickness from 0.1 to 4.8 mm. ¹

**Fig. 63.1** Frontal sinus development. (Courtesy of the AO Foundation/AO Surgery Reference.)

**Fig. 63.2** Anterior and lateral views of the frontal sinus demonstrating a thick anterior table and relatively thin posterior table. The floor of the sinus forms the medial portion of the orbital roof. The posterior table forms a portion of the anterior cranial fossa. The anterior table forms part of the forehead, brow, and glabella. (Courtesy of the AO Foundation/AO Surgery Reference.)

The nasofrontal recess is the sole outflow tract for the frontal sinus. The distance from the frontal sinus to the hiatus semilunaris is usually very short and is therefore most accurately described as a “recess” rather than a true duct. Each ostium is 1–3 mm in diameter and located on the posterior, inferior aspect of the sinus floor. The ostium lies anterior to the anterior ethmoid air cells, medial to the orbit, lateral to the intersinus septum, and posterior to the frontal bone. The true ostium represents the narrowest point of an hourglass configuration, with the frontal sinus infundibulum above and the nasofrontal recess below ( Fig. 63.3 ). ² The vascular supply to the frontal sinus is from the supraorbital and supratrochlear arteries via the internal carotid system. Venous drainage occurs through three pathways: the facial vein, the ophthalmic vein (to the cavernous sinus), and the foramina of Breschet (to the subarachnoid space). ⁶ The ophthalmic branch of the trigeminal nerve provides sensory innervation to the frontal sinus.

**Fig. 63.3** The frontal sinus drainage pathway has an hourglass configuration with the infundibulum above and the frontal sinus below. (Courtesy of the AO Foundation/AO Surgery Reference.)

Epidemiology

The frontal sinus is protected by thick cortical bone and is more resistant to fracture than any other facial bone ( Fig. 63.4 ). ³ Consequently, frontal sinus fractures account for only 5 to 15% of maxillofacial injuries and are most commonly associated with motor vehicles accidents, sporting events, and assaults. ⁴ The extreme force required to fracture the anterior table of the frontal sinus results in serious associated injuries in many patients. ⁵ Sixty-six percent of patients will have associated facial fractures. Isolated anterior table fractures occur 33% of the time. Combined fractures of the anterior table, posterior table, and/or the nasofrontal recess account for 67% of frontal sinus injuries. Isolated posterior table injuries occur but are very uncommon. ⁴

**Fig. 63.4** The anterior table of the frontal sinus is very thick and extremely resistant to injury. The figure shows the force required to fracture each structure. (Nahum AM. The biomechanics of maxillofacial trauma. Clin Plast Surg 1975;2:63. Reprinted by permission).

Diagnosis

The accurate diagnosis of frontal sinus fractures and nasofrontal recess injuries is crucial to appropriate treatment. After the patient has been stabilized, a thorough head and neck examination should be performed. Patients with frontal sinus fractures often complain of forehead pain and swelling. Other findings that may suggest a frontal sinus injury include supratrochlear and supraorbital paresthesias, epistaxis, forehead abrasions, lacerations, and hematoma. Through-andthrough injuries of the frontal sinus have high morbidity and prompt surgical treatment is indicated. If the patient is awake, he or she should be questioned regarding the presence of clear rhinorrhea or salty postnasal drainage. Drainage suspicious for cerebrospinal fluid (CSF) rhinorrhea can be grossly evaluated with a “halo test.” The bloody fluid is allowed to drip onto filter paper. If CSF is present, it will diffuse faster than blood and result in a clear halo around the blood. The definitive test for CSF is β-2 transferrin. The presence of β-2 transferrin is diagnostic of a skull base injury with CSF leak. The only other locations where β-2 transferrin is found are the vitreous humor of the eye and perilymph of the inner ear.

Radiological Evaluation

Historically, plain sinus X-rays were used to evaluate facial fractures. Thin cut (1–1.5 mm) axial computed tomography (CT) scans are now the gold standard for diagnosis of frontal sinus fractures. These images are readily reformatted into coronal, sagittal, and threedimensional (3D) reconstructions to improve the diagnostic accuracy. Axial cuts provide excellent information about the anterior and posterior table as well as pneumocephalus ( Fig. 63.5 ). Coronal reconstructions demonstrate the frontal sinus floor, orbital roof, and frontal recess ( Fig. 63.6 ). Sagittal views can assist with evaluation of frontal recess and skull base injuries ( Fig. 63.7 ). Threedimensional reconstructions can be very helpful in delineating the location of bone fragments and reducing the need for excessive dissection intraoperatively ( Fig. 63.8 ). Access to the PACS ( p icture a rchiving and c ommunication s ystem) or some type of presurgical planning software allows the surgeon to manipulate the reconstructions in space, gaining a greater understanding of depth and spatial relationships of the injury ( Video 63.1).

**Fig. 63.5** Axial CT scan of a complex frontal sinus fracture. Note the displaced posterior table bone fragments (*white arrow*) and pneumocephalus (*black arrow*).

**Fig. 63.6** Coronal CT scan of a complex frontal sinus fracture. Note the involvement of the medial orbital wall and the frontal recess (*white arrows*).

**Fig. 63.7** Sagittal CT scan of a complex frontal sinus fracture. Note the involvement of the frontal recess.

**Fig. 63.8** Threedimensional reconstruction of a complex frontal sinus fracture. The threedimensional representation gives the surgeon a better understanding of the size and location of the bone fragments. This can reduce the need for soft tissue dissection during surgery.

Treatment Algorithm (Fig. 63.10)

The treatment goals for frontal sinus fractures include (in decreasing order of importance) protection of intracranial contents, prevention of early and late complications, restoration of aesthetic forehead contour, and return of normal frontal sinus function. Accomplishing all of these goals is not always possible. However, reconstruction of a “safe” sinus is imperative. Once this has been accomplished, the aesthetic and functional repair can be addressed. The appropriate treatment strategy can be determined by assessing four anatomical parameters: (1) anterior table fracture, (2) posterior table fracture, (3) nasofrontal recess fracture, and (4) dural tear (CSF leak) ( Fig. 63.9 ); and applying them to the algorithm presented in Fig. 63.10 . Specific treatment options include observation, endoscopic fracture reduction or camouflage, open reduction and internal fixation, sinus obliteration, sinus exenteration (Riedel procedure), and sinus cranialization. The indications and techniques for each are discussed below.

**Fig. 63.9** Illustration of the anatomic parameters used to determine a treatment plan for frontal sinus fractures; these include (A) anterior table fracture, (B) posterior table fracture, (C) nasofrontal recess fracture, and (D) dural tear (cerebrospinal fluid leak). (Courtesy of the AO Foundation/AO Surgery Reference.)

**Fig. 63.10** Algorithm for treatment of frontal sinus fractures. CSF, cerebrospinal fluid; FESS, functional endoscopic sinus surgery.

Nasofrontal Recess Fractures (Fig. 63.10)

The compact structure of the nasofrontal recess makes accurate diagnosis of isolated fractures difficult. A thorough physical examination and a thin cut CT scan with 3D reconstructions should be critically reviewed. Radiographic findings that are most suggestive of a frontal recess injury include fractures involving the: floor of the frontal sinus, anterior ethmoid region, or gross disruption of the outflow tract. ⁹ , ¹⁰ , ¹¹ In the absence of significant fracture displacement or associated frontal sinus injuries, there has been a trend toward a more conservative approach to these injuries. This would include close observation and a repeat CT scan 4 to 6 weeks after the injury. If the nasofrontal recess is found to be obstructed and the frontal sinus is opacified, surgical treatment is indicated (see below).

More recent literature has suggested that open reduction and internal fixation of frontal sinus fractures involving the frontal recess, followed by close postoperative observation, may be efficacious. ¹² If outflow obstruction becomes apparent weeks to months after the injury, an endoscopic sinusotomy can be performed. The author has had some success with this technique, but there is limited longterm followup. This approach is still being investigated and should be reserved for surgeons with extensive experience with traditional open approaches to the frontal sinus as well as endoscopic frontal sinusotomy.

Anterior Table Fractures (Fig. 63.10)

Isolated, minimally displaced (0–2 mm) fractures of the anterior table pose little risk for mucocele formation, and rarely result in aesthetic or functional deficit ( Fig. 63.11 ). The small risk of external deformity should be discussed with the patient; however, these injuries are best managed nonoperatively. Fractures with greater displacement (2–6 mm) present little risk of mucocele formation and often do well with no intervention ( Fig. 63.12 ). However the risk of aesthetic deformity likely increases as the degree of displacement increases. The decision for surgery in these patients should NOT be based on the risk of longterm functional sequelae. The decision for surgery should be carefully weighed against the risks of general anesthesia and iatrogenic sequelae (alopecia, paresthesias, facial nerve injury, etc.). Such sequelae can often be more significant than the injury itself. Minimally invasive approaches to fracture reduction have been described, accessing the frontal bone via an upper eyelid ¹³ , ¹⁴ or scalp incision. ¹⁵ , ¹⁶ , ¹⁷ These approaches are technically challenging and generally require significant expertise with endoscopic techniques. If an endoscopic approach is chosen, the author prefers a camouflage technique. ¹⁵ , ¹⁶ , ¹⁸ Endoscopic camouflage is performed 2–3 months after the injury when all facial swelling has resolved and the patient is able to assess if an aesthetic deformity actually exists. If the patient is seen acutely and an endoscopic camouflage repair is planned, the rational and indications for such an approach must be discussed (i.e., risk of iatrogenic injury may be greater than the traumatic deformity itself). The patient must also understand that the fracture cannot be reduced once it has healed. In the author’s experience, patients with mildly displaced fractures will often choose no further treatment for these injures because there is little if any external deformity. More complex fractures (> 6 mm displacement or with significant comminution) will require an open reduction using a coronal incision ( Fig. 63.13 ).

**Fig. 63.11** Axial CT scan demonstrating a minimally displaced (< 2 mm) anterior table fracture.

**Fig. 63.12** Axial CT scan and photograph demonstrating a mildly displaced (2–6 mm) anterior table fracture. Note that the deformity can be seen on CT, but is not evident clinically.

**Fig. 63.13** Axial CT scan demonstrating a severely displaced and comminuted anterior table fracture.

Posterior Table Fractures (Fig. 63.10)

Treatment of posterior table fractures is complex and controversial due to the risk of CSF leak, meningitis, brain injury, and late mucocele formation. ⁵ , ¹⁹ Some authors have supported exploration of nearly all posterior table fractures, while others recommend observation of even displaced posterior table injuries. This author believes the primary decision criteria for surgical intervention are the fracture severity (displacement/comminution) and the presence of a CSF leak.

Displacement ≤ 2 mm

Patient with ≤ 2 mm of displacement and no CSF leak can be observed. A repeat CT scans at 1 month and 1 year is indicated to rule out mucocele formation. The need for longterm followup should be emphasized with the patient, including the signs and symptoms of a mucocele. If a CSF leak is present upon presentation, observation is still indicated. Approximately 50% of these will resolve spontaneously. ²⁰ If the leak persists, a sinusotomy, dural repair, and sinus obliteration are indicated.

Displacement. 2 mm

Patients with > 2 mm of displacement, no CSF leak, and minimal comminution should be considered for sinus obliteration. More severe injuries with a frank CSF leak and moderate to severe comminution will require a dural repair with removal of posterior table bone. If more than 25 to 30% of the posterior table bone is removed, a cranialization should be considered. Neurosurgical consultation should be obtained for assistance with brain debridement and dural closure.

Surgical Technique

Frontal Sinusotomy and Endoscopy

Endoscopic frontal sinusotomy can be used to visualize the posterior table and frontal recess for evidence of CSF leak. After appropriate consent is obtained for the procedure (including the risks of bleeding, infection, paresthesia, posterior table injury, and poor aesthetic result), local anesthesia is injected and a 1- to 1.5-cm skin incision is placed midway between the medial canthus and the glabella, and 1 cm inferior to the brow ( Fig. 63.14 ). The incision should not be placed within the eyebrow as this increases the risk of supratrochlear nerve injury and alopecia. The incision is best hidden by placing it medial and inferior to the curve of the brow. A scalpel is used to incise the skin, and a guarded needle point monopolar electrocautery is used to expose the periosteum. The location of the frontal sinus is confirmed on the CT scan or with intraoperative navigation. A small cutting bur is used to open a 4- to 5-mm frontal sinusotomy, 1 cm medial and inferior to the medial brow ( Fig. 63.15 ). The mucosa is incised sharply. Direct visualization of the posterior table and nasofrontal recess is performed with a 30-degree nasal endoscope ( Fig. 63.16 ). A flexible pediatric bronchoscope can be used to assess the lateral aspect of the sinus if necessary. A Valsalva maneuver can assist with the diagnosis of a CSF leak. The procedure is completed with a meticulous, layered closure. Trephination can be performed bilaterally if necessary.

**Fig. 63.14** Illustration of a frontal sinus trephination. The incision should be placed midway between the medial canthus and the glabella, and approximately 1 cm inferior to the brow. The incision is best hidden when placed inferior to the forehead curvature. (Courtesy of the AO Foundation/AO Surgery Reference.)

**Fig. 63.15** Illustration of a cutting bur being used to trephinate the frontal sinus. Care should be used to avoid posterior table injury. (Courtesy of the AO Foundation/AO Surgery Reference.)

**Fig. 63.16** Endoscopic view of a posterior table fracture with CSF leak. (Courtesy of the AO Foundation/AO Surgery Reference.)

Endoscopic Anterior Table Repair

Appropriate consent should be obtained for the procedure including the risks of bleeding, infection, paresthesia, alopecia, poor aesthetic result, and possible need for open approach if an endoscopic repair cannot be performed. A 3- to 5-cm parasagittal “working” incision should be placed above the fracture, 3 cm behind the hair line ( Fig. 63.17 ). Care should be taken to minimize trauma to the hair follicles—avoiding electrocautery if possible. The incision length should be kept to a minimum, but will vary depending on the size of the fracture and implant to be inserted. A second 1- to 2-cm endoscope incision is then placed at the same height, 6 cm medial to the working incision. In patients with a prominent forehead or receding hair line, the incisions may need to be placed closer to the hairline, allowing visualization around the forehead curvature.

**Fig. 63.17** Illustration of (A) “working” and (B) “endoscope” incisions used for endoscopic repair of anterior table frontal sinus fracture. (Courtesy of the AO Foundation/AO Surgery Reference.)

The surgical technique is similar to that of an endoscopic brow lift. ²¹ A “blind” subperiosteal dissection is performed down to the level of the fracture. Caution should be used to maintain the integrity of the periosteal envelope. Periosteal tears will catch the endoscope when it is inserted and make visualization more difficult. A 4-mm, 30-degree endoscope (with rigid endosheath and camera) is inserted to visualize the optical cavity. The periostoma is carefully elevated over the defect. The elevation is generally not difficult because the procedure is performed ≥ 3 months after the injury and there is a fibrous layer preventing entry into the sinus ( Fig. 63.18 ). An “0 silk” stitch can be placed full thickness through the forehead skin and used for retraction, maximizing the optical cavity ( Fig. 63.19 ). Once the entire fracture is exposed, a 0.85-mm thick porous polyethylene sheet (MEDPOR, Stryker) is trimmed to approximate the defect. The implant size can be estimated by using the forehead depression as a template ( Fig. 63.20 ). The superior edge of the implant is marked with a pen to maintain the orientation endoscopically. The implant is inserted through the working incision and manipulated over the defect ( Fig. 63.21 ). This process is repeated until the diameter of the implant is 2 to 3 mm larger than the defect. At times, the author has sutured two to three layers of MEDPOR together to more accurately fill deep defects. A 25-gauge needle is then passed through the skin over the fracture site and endoscopically visualized to determine the best site for percutaneous screw placement. A no. 11 blade is used to make a 2-mm, throughandthrough stab incision at the edge of the implant. A 1.7-mm self-drilling screw (length 4–7 mm) is passed through the stab incision, through the edge of the implant, and into the frontal bone ( Fig. 63.22 ). If the implant is not completely stable, a second screw is placed on the contralateral side. The self-drilling screw must be placed at least 0.5 to 1.0 mm away from the implant edge, or the implant may tear. The scalp incisions are then closed in layers and a head dressing is applied. Not all isolated anterior table fractures are appropriate for this technique. Injuries with severe comminution and marked mucosal injury may require open reduction or even frontal sinus obliteration. Fractures that extend over the orbital rim may be difficult or impossible to visualize endoscopically and may also require an open approach ( Fig. 63.23 ).