# Frontal Sinus Fractures

## Overview

Frontal sinus fractures account for 5-15% of all facial fractures. They result from high-energy impact to the forehead (MVC, assault, falls, sports) and require significant force (800-1600 pounds) due to the thickness of the anterior table. Management depends on involvement of the anterior table, posterior table, and nasofrontal outflow tract (NFOT). Improper management can lead to life-threatening intracranial complications including meningitis, brain abscess, and mucocele.

## Anatomy

The frontal sinuses are paired pneumatized cavities within the frontal bone. The anterior table is thick cortical bone forming the forehead contour and is the strongest part of the facial skeleton. The posterior table is thin cortical bone forming the anterior wall of the anterior cranial fossa, lined by dura. The nasofrontal outflow tract is the drainage pathway from the frontal sinus to the middle meatus via the frontal recess and ethmoid infundibulum, with the narrowest portion being the frontal ostium (3-4 mm diameter). NFOT patency is critical for sinus health, as obstruction leads to mucocele formation. The sinus mucosa consists of respiratory epithelium (ciliated pseudostratified columnar) that produces mucus. The intersinus septum separates right and left sinuses and is often asymmetric. Approximately 4-5% of adults have aplastic or hypoplastic frontal sinuses.

## Classification

### By Anatomic Involvement

Anterior table fractures alone are the most common pattern and can be nondisplaced, displaced (greater than 1-2 mm or the width of the anterior table), or comminuted. Posterior table fractures can be nondisplaced, displaced, or comminuted. NFOT involvement may be present in any pattern. Combinations include anterior plus posterior, anterior plus NFOT, and all three components.

### Associated Injuries

CSF leak from posterior table disruption with dural tear occurs in 33-75% of posterior table fractures. Associated intracranial injuries include epidural or subdural hematoma and pneumocephalus. Orbital roof fractures, NOE fractures, and brain contusion or laceration may also be present.

<image>Sagittal and coronal CT images of the frontal sinus showing the anterior table, posterior table, and nasofrontal outflow tract with annotations, alongside a classification diagram showing the different fracture patterns (isolated anterior table, anterior table with NFOT involvement, posterior table involvement, and combined patterns) with the corresponding management algorithm</image>

## Diagnosis

### Clinical Findings

Clinical findings include forehead laceration, depression, or contusion, crepitus over the forehead (subcutaneous emphysema), forehead contour depression (which may be masked by edema), CSF rhinorrhea (clear fluid from the nose, assessed with the halo test and beta-2 transferrin), pneumocephalus (air intracranially seen on CT), periorbital ecchymosis, and frontal sinus tenderness.

### Imaging

CT of the face and head (axial, coronal, sagittal) is the gold standard. It evaluates anterior and posterior table integrity, assesses the NFOT (looking for fracture lines through the frontal recess and ethmoid infundibulum), identifies CSF leak (opacification, air-fluid level in the sinus, pneumocephalus), and provides 3D reconstruction for surgical planning. Thin-cut coronal views are best for evaluating the NFOT and posterior table. CT angiography is obtained if there is concern for dural sinus or major vessel injury.

## Management Algorithm

### Anterior Table Fractures Only

#### Nondisplaced

Nondisplaced anterior table fractures are observed with sinus precautions (no nose blowing). Follow-up CT at 4-6 weeks confirms healing and NFOT patency. Mucocele development is monitored but is rare in nondisplaced fractures.

#### Displaced (Cosmetic Deformity)

ORIF of the anterior table involves reduction and fixation with miniplates (1.0-1.5 mm) and screws. The approach is through a coronal incision (standard), open sky approach, or through an existing laceration. If the NFOT is intact, the anterior table is repaired and sinus function is preserved. If the NFOT is injured, specific NFOT management is required.

### Posterior Table Fractures

#### Nondisplaced, No CSF Leak

Nondisplaced posterior table fractures without CSF leak are observed with serial imaging and endoscopic monitoring of the sinus. The risk of intracranial complication is low.

#### Displaced (Less Than 1 Posterior Table Width) Without CSF Leak

Management is controversial, with options including observation versus surgical exploration. Many advocate observation with close follow-up. If the NFOT is patent, the sinus may be preserved.

#### Displaced (Greater Than 1 Posterior Table Width) or CSF Leak

Surgical management is required. Options include sinus obliteration (stripping all sinus mucosa, obliterating the NFOT, filling the sinus with autogenous material such as fat, bone, or hydroxyapatite, and repairing the anterior table) and sinus cranialization (removing the posterior table, collapsing the anterior table posteriorly to obliterate the sinus space, and allowing the brain to expand into the former sinus space). Dural repair is performed if CSF leak is present, using primary closure or a pericranial flap.

#### Comminuted Posterior Table

Comminuted posterior table fractures usually require cranialization and are often associated with dural laceration and intracranial injury. Neurosurgical collaboration is needed for the intracranial component.

### Management Summary by Pattern

| Fracture Pattern | NFOT Status | Management |
|---|---|---|
| Anterior table, nondisplaced | Intact | Observation, sinus precautions |
| Anterior table, displaced | Intact | ORIF of anterior table |
| Anterior table, displaced | Damaged/obstructed | ORIF + sinus obliteration |
| Posterior table, nondisplaced, no CSF | Intact | Observation with serial imaging |
| Posterior table, displaced or CSF leak | Any | Obliteration or cranialization + dural repair |
| Posterior table, comminuted | Any | Cranialization + neurosurgical collaboration |

### NFOT Involvement

NFOT obstruction is the key concern, as it leads to mucocele formation months to years later. NFOT patency is assessed by CT findings (fracture through the frontal recess, displacement of fragments into the NFOT) and intraoperative visualization. If the NFOT is patent and intact, sinus function is preserved and fractures are repaired with ORIF. If the NFOT is injured but potentially reconstructable, some advocate stenting (controversial) or endoscopic repair. If the NFOT is irreparably damaged, sinus obliteration eliminates the mucocele risk.

### Sinus Obliteration Technique

The procedure begins with a coronal approach and exposure of the frontal sinus. An osteoplastic flap removes the anterior table as a single piece or reduces displaced fragments. All sinus mucosa is stripped meticulously, and a diamond bur is used on all bony surfaces to ensure no mucosal remnants. The NFOT is obliterated with bone, cartilage, or muscle to prevent intracranial contamination. The sinus cavity is filled with autogenous fat (from abdominal harvest), pericranial flap, or bone graft. The anterior table is replaced and fixated. Failure to completely remove mucosa leads to mucocele formation years later.

### Sinus Cranialization Technique

The procedure uses a coronal approach with craniotomy or access through the posterior table fracture. All posterior table fragments are removed, and all sinus mucosa is stripped from the anterior table and sinus walls. The NFOT is obliterated. The brain, covered by dura, expands into the sinus space. The anterior table is repaired or reconstructed for contour. A pericranial flap may be draped between the brain and the anterior table.

<image>Step-by-step illustration of frontal sinus obliteration showing the coronal approach, osteoplastic flap elevation, meticulous mucosal stripping with diamond bur, NFOT obliteration with bone, filling the sinus cavity with abdominal fat, and anterior table replacement with miniplate fixation</image>

## Endoscopic Approaches

Endoscopic-assisted repair of anterior table fractures is an emerging technique. Endoscopic Draf procedures can reconstruct the NFOT. Endoscopic monitoring of the frontal sinus after injury provides surveillance for mucocele. Advantages include reduced morbidity compared with the coronal approach, but limitations include unsuitability for comminuted or complex posterior table injuries.

## Complications

Mucocele and mucopyocele are the most feared late complications. Entrapped mucosa continues to produce mucus, forming an expanding cystic lesion that causes bony erosion and may extend intracranially. This may present years to decades after injury, and prevention depends on complete mucosal stripping and NFOT obliteration. Meningitis and brain abscess result from communication between the sinus and intracranial space. Persistent CSF leak may require a lumbar drain or surgical repair. Contour deformity results from inadequate anterior table reduction or resorption of obliteration material. Frontal sinusitis occurs if the sinus is preserved with impaired drainage. Osteomyelitis of the frontal bone (Pott puffy tumor, a subperiosteal abscess with overlying edema) is another potential complication.

## Controversies

The choice between obliteration and cranialization has advocates for both approaches, with cranialization potentially preferred for posterior table fractures as it eliminates the sinus space entirely. There is a growing trend toward conservative management of minimally displaced posterior table fractures with close follow-up rather than surgical exploration. Endoscopic approaches have expanding indications but limited evidence for complex injuries. NFOT assessment is difficult, as long-term patency is hard to predict from CT alone, making intraoperative assessment the gold standard. Autogenous fat is the traditional obliteration material, but hydroxyapatite and other materials are being studied.

## Clinical Pearls

Frontal sinus fractures require high-energy impact, so associated intracranial injury should always be sought. The posterior table is the critical determinant of management -- nondisplaced anterior table fractures are usually benign, while posterior table involvement changes everything. Mucocele prevention is the long-term goal, and meticulous mucosal stripping cannot be overemphasized. If the NFOT is damaged beyond repair, the sinus must be obliterated, as a nonfunctioning sinus is a ticking time bomb for mucocele. CSF rhinorrhea in frontal sinus fractures indicates a dural tear; most resolve with conservative management (head elevation, avoidance of straining), but persistent leaks require surgical repair. Long-term follow-up (5-10+ years) is essential after frontal sinus surgery because mucoceles can develop decades later. The coronal approach provides the best exposure but carries risks including alopecia along the incision, supraorbital nerve paresthesia, and temporal hollowing. Neurosurgical collaboration is essential for posterior table fractures with intracranial injury.

## References
- Bell RB, et al. Management of frontal sinus fractures. J Oral Maxillofac Surg. 2016.
- Rodriguez ED, et al. Twenty-six-year experience treating frontal sinus fractures: a novel algorithm based on anatomical fracture pattern and failure of conventional techniques. Plast Reconstr Surg. 2008.
- Manolidis S, Hollier LH. Management of frontal sinus fractures. Plast Reconstr Surg. 2007.
- Strong EB, et al. Frontal sinus fractures: a 28-year retrospective review. Otolaryngol Head Neck Surg. 2006.
- Tiwari P, et al. Operative management of frontal sinus fractures: a systematic review. JAMA Facial Plast Surg. 2015.
- Montovani JC, et al. Management of frontal sinus fractures: treatment algorithm. Int Arch Otorhinolaryngol. 2006.