Naso-Orbito-Ethmoid Fractures

Etiology

The NOE fracture pattern is caused by forceful trauma to the upper central midface. Due to the high energy involved, these fractures often occur in combination with injuries to other parts of the face and body. Road traffic collisions are the most common cause of NOE fractures, especially involving motorcycles.[5] Fortunately, the incidence of NOE fractures appears to be on the decline. The introduction of seatbelts and airbags has helped to decrease the overall frequency of facial fractures.[2] Physical assault, sport, and horse kicks have also been associated with this fracture pattern.

Epidemiology

NOE fractures make up 5% of all facial fractures in adults, with young males most commonly affected.[6][7] In the pediatric population, the proportion is higher, at 16% of facial fractures overall.[8] In the United States, facial fractures cost approximately $1.06 billion per year, with 93,808 associated hospital days.[9]

Pathophysiology

The naso-orbito-ethmoid complex is a confluence of structures made up of the nasal bones, the nasal processes of the frontal bone, the frontal processes of the maxillae, the lacrimal bones, the laminae papyraceae of the ethmoid bone, and the sphenoid bone.[1] Central to the concept of the NOE region is the medial canthal tendon (MCT), also called medial palpebral tendon, which is a band of fibrous tissue originating from the medial palpebral part of the orbicularis oculi muscle as well as from the superior and inferior tarsal plates of the eyelids. The MCT splits and surrounds the lacrimal fossa, which contains the lacrimal duct, before inserting into the lacrimal crest of the maxilla anteriorly and into the lacrimal bone posteriorly.[10]

The facial skeleton is underpinned by four horizontal buttresses, and four paired vertical buttresses, which are columns of bone that provide the horizontal and vertical dimensions of the face, support for muscle action, and resistance to deformation with impact. The NOE complex incorporates the medial vertical and inferior and superior horizontal buttresses. Reconstructing these is the focus during surgical reduction and fixation of NOE fractures. It has been suggested that the pattern of NOE fractures clinically observed is the result of facial bone design; the nasal bones are thin and transmit force posteriorly to the lacrimal and ethmoid bones, which crumple and thus spare the contents of the cranial vault and orbits.[11] It is unclear, however, whether facial bone fractures truly provide any protection to the brain itself.[12] 

Sensory innervation to the NOE region occurs through the ophthalmic and maxillary branches of the trigeminal nerve. Motor innervation comes from the zygomatic branches of the facial nerve. The lacrimal nerve transmits sympathetic and parasympathetic fibers to the lacrimal gland; sympathetic fibers also provide innervation to Mueller's muscle, elevating the eyelid when stimulated. 

Arterial supply to the NOE region originates from the internal and external carotid arteries. The facial and maxillary arteries are given off by the external carotid artery and perfuse the majority of the face. The ophthalmic artery, originating from the internal carotid artery, supplies blood to the orbital contents. The ophthalmic artery also gives rise to the anterior and posterior ethmoidal arteries, which perfuse the ethmoid sinuses and terminate in the nasal cavity. These arteries anastomose with the sphenopalatine artery to form Little's area, which is responsible for the majority of epistaxis.[13] The venous outflow of the NOE region drains into the cavernous sinus, which can result in complications from thrombosis secondary to trauma or infection.[14]

History and Physical

An advanced trauma life support approach should be adopted when assessing patients with suspected facial trauma. Airway patency and stability are key priorities alongside cervical spine immobilization and hemorrhage control, as 10% of complicated facial fractures are associated with significant bleeding.[15] Full neurological and ophthalmic examinations are indicated as well because two-thirds of facial fractures are associated with some form of ocular injury.[16]

Examination of the NOE complex begins with a visual and manual inspection, which often will reveal severe swelling and periorbital ecchymosis that make examination a challenge. Excessive tear overflow in the eye and face (epiphora) can be associated with lacrimal duct damage or obstruction. A more reliable assessment of lacrimal canalicular function uses dye tests or dacryocystography (radiological contrast assessment of the lacrimal apparatus) if epiphora is persistent following surgery.[17] Depressed nasal bone and septal fractures may result in decreased nasal dorsal projection with an associated upturn of the nasal tip.[18] Epistaxis with mucosal disruption may be present with or without cerebral spinal fluid (CSF) rhinorrhea if the floor of the anterior cranial fossa or the posterior table of the frontal sinus is fractured. The presence of CSF in rhinorrhea can be confirmed with a beta-2-transferrin test, which is more accurate but far slower than looking for a halo sign (CSF fluid on filter paper forming a halo pattern, diffusing farther radially than the blood products). Nasal patency can be rapidly assessed by placing a metal object under the nostrils and looking for fogging with exhalation.

Assessment of the MCT is a fundamental aspect of determining the severity of an NOE complex injury. Telecanthus, also known as pseudohypertelorism, is a cardinal sign of MCT rupture; it appears as an increased distance between the medial canthi with an unchanged interpupillary distance. The intercanthal distance is, on average, 30 to 31 mm, and the average interpupillary distance is 62 mm for females and 64 mm for males. An intercanthal distance greater than 40 mm is noticeably wide and constitutes an indication for surgical correction.[19] Another method of evaluating the integrity of the MCT is the bow-string test, which involves palpating the nasal root while retracting the eyelid inferolaterally; if the MCT is compromised, the eyelid will have greater laxity, and a fractured segment may be palpable.

Evaluation

Investigations

The physical examination may be initially limited by severe pain and gross swelling of facial structures. Non-contrast, fine-cut computed tomography (CT) scanning of the head provides definitive details of soft tissue and bony injuries. Using both 3-dimensional and 2-dimensional images in coronal and axial views facilitates the diagnosis and staging of NOE complex fractures and assists the operating team in planning reduction and fixation.[20] Three-dimensional reconstruction images are also very useful for demonstrating the extent of the injuries to patients and family members who may not be familiar with cross-sectional anatomy. The planned surgical approach, degree of exposure, and equipment required are ultimately dependent upon the CT scan results. The study also reveals any injuries of other structures within the head. In a polytrauma setting, the CT scan is likely to be performed as soon as the patient is stabilized.

Classification

The Markowitz and Manson system is the most widely used classification system for NOE fractures and is based on the integrity of the MCT because its status determines the complexity of the reconstruction required.[3] This classification system relies on both CT scan and clinical examination in order to determine the status of NOE complex structures and MCT integrity, respectively:

• Type 1: The MCT is attached to a large bone fragment.
• Type 2: The MCT is attached to a comminuted bone fragment.
• Type 3: The MCT is avulsed from the bone.

Treatment / Management

Naso-orbito-ethmoid complex fractures require surgical fixation and/or reduction to restore the aesthetic contours and proportions of the face. If the medial canthal tendon is avulsed, it will need to be reduced. Pre-injury photographs can inform the reduction and fixation process to return, as close as possible, the face to its original appearance. The surgical approach will depend on the severity and distribution of fractures; an effort should be made to use the smallest incision possible that will provide the necessary exposure to minimize the aesthetic impact of the postoperative scar.[1] Sometimes facial lacerations or pre-existing scars can be utilized for access.

The coronal incision provides good exposure of the upper midface and is the gold standard approach to NOE fractures that involve the frontal sinus. The midface degloving approach provides greater exposure of the lower midface; this technique, however, is associated with a number of complications, such as postoperative anesthesia and nasal deformity. After complete exposure of the fractures, the first priority is the reduction and fixation of the bony segments.[21] In type 1 NOE fractures, a closed reduction can typically be achieved. Type 2 and type 3 fractures will require exposure of the fractured segments with open reduction and internal fixation. A titanium mesh is often used to stabilize the medial orbital wall, although absorbable meshes can also be used.[22] Microplates and screws are used to fix and stabilize bone fragments and to reconstitute the horizontal and vertical buttresses. Frontal sinus involvement may necessitate additional bony reduction and fixation as well as cranialization of the sinus or obliteration of its outflow tracts, although the details of these procedures are beyond the scope of this article.[23](B3)

In type 3 NOE complex fractures, reduction of the MCT (canthopexy) is achieved via transnasal wiring, which is performed by drilling a small hole into the medial orbital wall and tethering the MCT with a wire. The use of a needle to secure the MCT in lieu of a drill is sometimes necessary for unstable comminuted fractures of the medial orbital wall.[24] As a general rule, the intercanthal distance should be overcorrected, i.e., narrowed beyond the normal intercanthal distance to compensate for the lateralization that inevitably occurs postoperatively.

Disruption to the lacrimal canalicular system is a common complication of midfacial trauma, with epiphora reported immediately postoperatively in nearly half of patients. Long-term epiphora, however, is relatively uncommon.[25] For this reason,  dacryocystorhinostomy is performed in a delayed fashion, six months after fracture fixation if posttraumatic epiphora has not resolved, with the goal of correcting tear drainage and preventing future mucocele formation.[17](B2)

Differential Diagnosis

Naso-orbito-ethmoid complex fractures seldom occur in isolation, without injury to other parts of the face or body. Other groups of facial fractures that can occur in isolation or alongside NOE complex fractures include:

• Zygomaticomaxillary complex fractures may occur with NOE fractures or independently. They are associated with a forceful lateral blow to the mid-lower face.[26]
• LeFort fractures are defined as the separation of the midface from the skull base and graded on a scale of 1 to 3, with one being the least severe and most common and 3 representing the bony separation of the face from the rest of the skull. LeFort fractures, by definition, must involve the pterygoid plates of the sphenoid bone, as these connect the skull base to the midface. Type 3 LeFort fractures also must include an NOE complex fracture, without which the facial skeleton could not be separated from the cranial vault.[27]
• Orbital floor fractures, also known as blowout fractures, in which a blow to the eye causes a fracture to propagate through the thin bone separating the maxillary sinus from the orbit, and occasionally the lamina papyracea of the medial wall of the orbit as well. In some cases, extraocular muscle or orbital fat herniates through the defect, causing diplopia and ophthalmoplegia.[28]
• Pan-facial fractures - these are fractures involving the upper, middle, and lower regions of the face.

Prognosis

The majority of patients who are treated with primary corrective surgery have acceptable aesthetic results. In severe type 3 fractures, some patients experience persistent nasal deformity.[29] Failure to correct telecanthus sufficiently on the first attempt makes subsequent revision very challenging.[21]

Complications

• Nasofrontal duct and or nasolacrimal duct disruption due to direct damage, displaced fracture segments, or iatrogenic injury.[17]
• Facial deformity, because perfect correction of telecanthus or nasal depression can be difficult to achieve, and some patients will retain a degree of asymmetry. Depending on the surgical approach, patients may experience temporary or permanent paralysis and or anesthesia of the forehead. Scars of the forehead may remain prominent in the long-term as well, particularly if tissue avulsion, infection, or involvement of the sebaceous glabellar skin occurs.[30]
• Infection of the incision site, soft tissues, and meninges.[30]
• Mucocele formation is a complication of sinus or lacrimal drainage disruption, and these can become infected, evolving into mucopyoceles.[30]
• Mental health issues, as patients with facial injuries, are at greater risk of developing post-traumatic stress disorder or anxiety-related disorders, particularly those who were victims of assault.[31]