General

While form and function are the underpinnings of facial anatomy, and generally speaking form is important for function, the facial architecture is also critically important aesthetically. Knowledge of facial skeletal anatomy is necessary for understanding the mechanisms and patterns of facial injuries as well as the approaches to their repair. Anatomic depictions are available in many anatomy texts and atlases; the focus herein is on aspects relevant to injury and repair.

The face can be arbitrarily divided into sections, each including bony anatomic structures and associated visceral and soft tissue entities. From superior to inferior, the frontal bones are generally considered the upper third of the face. The maxillae, zygomas, and orbits comprise the middle third, or midface, which may include the nose. Or, the nose and nasoethmoid complex may be separately considered as the central face. The mandible is generally considered the lower third, although the vertical (posterior) portions of the mandible extend superiorly to the skull base, which is well above the lower third.

Upper Third

The frontal bone forms the contour of the forehead. Displaced fractures can create various deformities, the most common of which is a central forehead depression (Fig. 23-1). The frontal bone forms the junction between the cranium and the face, and it relates to several visceral structures, the most critical of which is the brain. The typically paired frontal sinuses, when present (approximately 85% of the time), are housed completely within the frontal bones (Fig. 23-2). Frontal bone fractures may involve only the anterior sinus walls, in which case the fractures are significant only for sinus function and cosmesis; or they may involve the posterior wall of the sinus or extend beyond the sinus, in which case they are true skull fractures and become neurosurgical concerns as well. The supraorbital rims and roofs are also part of the frontal bones, which are therefore also related to the orbits, and fractures can thus affect orbital and ocular functions. Inferiorly in the midline, the glabella portion of the frontal bone relates to the superior extent of the nasal bones. This thick glabellar bone protects the underlying frontal outflow tracts and the cribriform plates, which house the branches of the olfactory nerves. The supraorbital and supratrochlear nerves pass through notches or foramina in the supraorbital rims and can be injured from trauma or, more commonly, from surgical manipulation.

Figure 23-1. Lateral view of a patient with a depressed central frontal fracture.

Figure 23-2. Front view of the craniofacial skeleton demonstrating the presence of the frontal sinuses within the frontal bone.

(Redrawn from Grant JCP. Grant’s Atlas of Anatomy. Baltimore: Williams & Wilkins; 1972, with permission.)

Middle Third

The middle third includes the zygomas, orbits, and maxillae, as well as the nose, which together with the anterior medial orbits form the central face. The anterior projection of the zygomas, the malar eminence, or “cheekbone prominences,” are important determinants of facial projection and contour. The posterolateral projections, the zygomatic arches, abut the temporal bones posteriorly and provide the attachments for the masseter muscles superiorly. The superior and medial projections of the zygoma contribute to the lateral and inferior orbital rims and the inferolateral orbital walls. Displacement of this portion of the zygoma can significantly alter the position of the globe in the orbit. The inferomedial extension of the zygoma extends from the inferior orbital rim and broadly contacts the maxilla, forming the important lateral buttress of the midface (Fig. 23-3). While the superior, medial, and inferior orbital rims extend anterior to the globe, the lateral rim, which is comprised primarily of the zygoma, is situated near the equator of the globe (Fig. 23-4).²⁴ Therefore minor changes in the position of the zygoma can have a significant impact on the anteroposterior position of the globe. Enophthalmos is a common complication of inadequately repaired or unrepaired zygomatic fractures.

Figure 23-3. Frontal (A) and lateral (B) view of the craniofacial skeleton demonstrating the broad attachment of the zygomatic bone to the maxilla extending from the infraorbital rim inferolaterally.

(Redrawn from Grant JCP. Grant’s Atlas of Anatomy. Baltimore: Williams & Wilkins; 1972, with permission.)

Figure 23-4. Schematic representation of axis of the globe extending from the lateral orbital wall to the lacrimal bone. The entire lateral wall is behind the axis of the globe, whereas only a portion of the floor is so situated.

(Redrawn from Pearl RM. Treatment of enophthalmos. Clin Plast Surg. 1992;19:99.)

The maxillae extend from the zygomas laterally to the nasal bones medially, forming the medial portions of the infraorbital rims and anterior orbital floors and support for the nasal bones. They also form the piriform apertures and house the nasolacrimal ducts. The maxillary dentition is important for mastication, and proper repositioning of the maxilla after trauma is critical to the recreation of a functional occlusion between the maxillary and mandibular teeth. Superomedially, the anterior lacrimal crest is formed by the maxillary bone. Fractures of this area often lead to malpositions of the medial canthal ligaments, which can result in telecanthus, an unsightly cosmetic deformity.

The maxilla also contains the infraorbital nerve, the terminal branch of V2, which provides sensation to the medial cheek, lateral nose, upper lip, and upper gingiva and teeth (Fig. 23-5). Fractures can compromise this nerve, and care must be taken to both preserve it and, if necessary, decompress it when repairing these fractures. The maxillae also house the maxillary sinuses, which drain into the middle meatus of the nose, lateral to the middle turbinates. Injury to the outflow tracts is uncommon, but preexisting obstruction may contribute to infection.

Figure 23-5. Front view of the partially dissected face. The infraorbital nerve is seen exiting the infraorbital foramen.

(Redrawn from Grant JCP. Grant’s Atlas of Anatomy. Baltimore: Williams & Wilkins; 1972, with permission.)

The nasal bones form the bony nasal projection and support the upper lateral cartilages, which form the internal nasal valves. Because of their prominent position in the middle of the face, the nasal bones are the most frequently fractured bones in the human body. Restoration of nasal function is important for breathing and olfaction, which also may have a significant impact on taste. The nasal bones are also cosmetically important, and suboptimal restoration of nasal contour is usually quite apparent. The nasal bones are supported by the frontal processes of the maxillae, which are anterior projections of the maxillae superomedially. Failure to identify fractures in this area can lead to unsatisfactory results of nasal fracture reductions.

The orbits are complex bony structures with structural contributions from multiple facial and skull bones. In addition to the frontal, zygomatic and maxillary contributions discussed earlier, the lacrimal bone sits behind the maxillary bone medially (Fig. 23-6). The maxillary bone and the lacrimal bone together form the lacrimal fossa, which houses the lacrimal sac. The strong anterior (maxillary bone) and posterior (lacrimal bone) lacrimal crests provide the sites of attachment of the components of the medial canthal ligaments. Note that the medial canthal ligaments have three components, an anterior, a posterior, and a superior attachment (Fig. 23-7). The thin lamina papyracea of the ethmoid bone completes the medial orbital wall. The palatine bone makes a small contribution posteroinferiorly. The posterior lateral orbit is provided by the greater wing of the sphenoid and the solid optic canal bone is contributed by the lesser wing of the sphenoid. The optic canal sits posteromedially behind the medial wall where it is generally protected from all but the severest injury. The optic foramen is actually directed toward the lateral orbital rim rather than directly anteroposterior. The important “orbital apex” includes the area lateral to the optic canal through which cranial nerves III, IV, V, and VI pass to enter the orbit, which is considered part of the superior orbital fissure. When pressure from an injury (or tumor, abscess, hematoma) causes dysfunction in these nerves, it is called superior orbital fissure syndrome, which requires urgent surgical intervention.^25,26

Figure 23-6. Bony orbital anatomy demonstrating the contributions of multiple bones.

(Redrawn with permission from Zide BM, Jelks GW. Surgical Anatomy of the Orbit. New York: Raven Press; 1985.)

Figure 23-7. A cut-away view of the medial canthal complex. In this view, a suture near the nose is around the superior component and the suture pulling laterally is around the anterior component, which has been severed. The posterior component is running behind the anterior component and is fixing the medial structures to the posterior lacrimal crest.

(Redrawn with permission from Zide BM, Jelks GW. Surgical Anatomy of the Orbit. New York: Raven Press; 1985.)

Familiarity with the complex shape of the orbital walls is important for repair. The position of the globe is determined by the orbital shape and contents. The best way to prevent globe malpositions is to restore the natural shape of the orbit and ensure that orbital fat that has escaped through fractures is returned to the orbit. While the orbital floor is gently concave inferolaterally, it tends to be more convex medially and becomes significantly convex posteriorly behind the equator of the globe (see Fig. 23-6). Familiarity with this anatomy increases the likelihood of proper repair after injury.

It is also important to understand the proper terminology associated with injuries. The term blowout fracture implies that the orbital rims have remained intact, while one or more walls of the orbit, typically the floor, though the medial wall are also commonly affected or have fractured. It also has implications for the mechanism of injury: a force transmitted by a blunt impact through the globe to the surrounding walls. Floor fractures can damage the infraorbital nerve, which runs through the floor of the orbit.

Midfacial structures are paired and the central bones are joined in the midline. The nasal bones and maxillae are joined vertically, and the palate forms the inferior horizontal bridge between the two maxillae. The upper horizontal bridge is formed by the anterior cranial base. There are horizontal connections across the nasal bones, but these are not straight across, because the nasal bones are situated on a line superior to the infraorbital rims, and posteriorly across the sphenoid. The relationships between the various bones are important not only when considering normal anatomy and its reconstitution, but also for understanding how facial architecture distributes biomechanical forces, which is important for the repair of fractured structures.

The concept of the “central face” comes into play only in the presence of injury and refers to injury in which the trauma to the solid nasal root is transmitted posteriorly resulting in a telescoping injury. This has variously been called naso-orbital fractures, fracture of the ethmoids,²⁷ nasoethmoid complex (NEC) fractures, and more recently naso-orbital-ethmoid (NOE) fractures. It is an important fracture clinically, but it takes on even greater significance when used as a paradigm for the understanding of how facial fractures occur and how the face is designed to provide maximum protection for structures important for the survival of the human organism.

The nose is important for airway, smell, and cosmesis, but it is less critical to human survival than vision or cerebral function. The solid glabellar and nasal root bones not only protect the underlying cribriform plate, but also take the first impact to the central face. Because the nasal bones and frontal processes of the maxillae are backed up by the thin laminae papyracea of the ethmoid bones, these latter provide little support and crumple, thereby allowing the nasal bones to “telescope” posteriorly while dissipating the shockwave into the ethmoid sinuses. The optic nerves are suspended in cushioning orbital fat anterior to the optic foramen and more posteriorly are protected by the thick bone of the lesser sphenoid wings once they enter the bony canal. Thus the medial orbits form a “crumple zone” to protect the globes and optic nerves in most central facial traumas.

This same concept can be applied to other aspects of facial skeletal anatomy. The globes tend to be protected in direct blunt trauma by the thin bones of both the orbital floors and medial walls. The globes are relatively round and suspended in fat so that most blunt traumas are transmitted to the thin orbital floors and medial walls, accounting for why “blowout fractures” are much more common than globe ruptures.^27a Similarly, the face itself functions as a “shock absorber” for the cranial cavity, so that the frequency and severity of brain injury can be limited. Finally, this theory provides an explanation for the presence of the paranasal sinuses that offers a survival advantage: that is, the sinuses serve as a crumple zone for the face,^27a allowing the energy to be dissipated before it reaches the eyes and brain. Thus the entire facial architecture has evolved by design to provide survival protection for critical organs (Table 23-1).

Table 23-1 “Survival Protection” Anatomic Structures

Lower Third

The mandible is generally considered the lower third of the facial structure. It contains the mandibular dentition, which interfaces with the maxillary dentition for mastication. Unlike the middle third, which is fixed to the skull, the mandible is mobile and swings, hinged to the skull base in two, bilaterally symmetric attachments. The hinges occur at the temporomandibular joints (TMJs), which are true arthrodial joints that both swing and slide. The conformation of the mandible, a somewhat horseshoe-shaped bone hinged in two places to the same solid entity, the skull, makes it well designed to absorb impact forces rather than transmit them to the solid middle fossa floor, and therefore multiple mandible fractures due to a single impact force are not uncommon. (Mandibular trauma causing injury to the skull base can occur, and the condylar head of the mandible has even rarely traversed the glenoid fossa, which houses the articular cartilage of the joint and entered the middle fossa, but such injuries remain rare.)²⁸ The condylar head of the mandible is housed within the TMJ and is connected to the vertical ramus by the relatively thin and weak condylar neck. This weak area of the bone seems to give easily when a contralateral impact is applied, and fractures of this neck area are generally called subcondylar fractures, indicating that they occur below the TMJ. A central impact to the mentum does not uncommonly result in bilateral subcondylar fractures. The condylar neck extends inferiorly into the vertical ramus, which is also relatively thin compared to the tooth-bearing body and symphyseal regions of the bone. However, fractures of the vertical ramus (other than extensions of subcondylar fractures) are relatively uncommon, presumably due to the protective effects of the muscular sling provided by the muscles of mastication, all of which attach to aspects of the vertical rami. The powerful masseter muscle attaches broadly to the inferolateral surface of the ramus, whereas the pterygoids attach to the medial surface. The temporalis attaches to the coronoid process, a superior extension of the anterior ramus. The angle region of the mandible occurs at the posterior extent of the tooth-bearing region and is a common area for fracture. Fractures here extend from the thick, tooth-bearing area in the third molar region posteroinferiorly into the much thinner bone of the ramus. The presence of the third molar tends to thin the bone superiorly, and tension of the muscle sling may also splint the area, creating a natural break point. Fractures in this region are particularly difficult to stabilize, and repairs have traditionally resulted in the highest rates of complications (see later). As might be predicted, the mandible is thickest in the tooth-bearing areas. The anterior portion from canine to canine is referred to as the symphyseal region or symphysis (sometimes arbitrarily divided into symphysis in the midline and parasymphyseal regions on either side of the midline). From canine to the angle of the body of the mandible contains the two premolar (bicuspid) and three molar teeth. Another unique aspect of mandibular anatomy is the presence of the inferior alveolar nerve. A branch of the third division of the trigeminal nerve, the inferior alveolar nerve enters the mandible at the lingula and travels beneath the tooth roots that it supplies, exiting the mental foramen as the mental nerve, generally in the region of the first bicuspid tooth. It is important to keep in mind when repairing mandibular fractures that the mental foramen does not generally represent the most inferior position of the nerve, and this must be considered when placing hardware on the mandible in the body region behind the mental foramen.

A common classification scheme for mandible fractures uses the terms favorable and unfavorable.²⁹ However, this scheme has no impact on management and is not addressed here. It is also important to be familiar with the changes that take place in the mandible with age and tooth loss. When people lose teeth, the normal stresses on the bone are significantly altered, and bone remodeling tends to result in atrophy of the alveolar portion of the bone. The tooth-bearing portions of the mandible atrophy from the top down, bringing the inferior alveolar nerve closer and closer to the oral surface; in extreme cases, it can even rest on top of the bone. In addition, atherosclerosis of the inferior alveolar artery occurs, limiting the blood supply to the thin atrophic bone.³⁰ This has significant implications for repair of these fractures.

Fractures of alveolar segments, tooth fractures, and tooth avulsions are beyond the scope of this chapter.

A knowledge of basic dental anatomy and familiarity with normal and common abnormal occlusal relationships is important for anyone treating fractures in the tooth-bearing facial bones. The normal adult complement of teeth is 32, with eight in each quadrant of the maxilla and mandible. Common numbering in adults in the United States is from 1 to 32, starting from the right maxillary third molar (number 1) counting toward the left with the left maxillary third molar being number 16, the left mandibular third molar being number 17, and ending with the right mandibular third molar being number 32. The dental surfaces contain cusps for chewing and grooves between these cusps, and in multicusp teeth these are identified by their positions as mesial (toward the incisors), distal (toward the posterior mandible or maxilla), buccal (toward the cheek), and lingual (toward the tongue). Occlusion is complex and has many aspects, but a normal molar relationship has been defined by Angle as the “mesiobuccal cusp of the maxillary first molar sitting within the mesiobuccal groove of the mandibular first molar.”³¹ This is Angle’s class I. When the maxillary molar is more anterior (chin generally relatively retruded), it is class II, and when the maxillary molar is more posterior (chin relatively prognathic), it is Angle’s class III. The maxillary arch should be wider than the mandibular, and when the maxillary buccal cusps fall lingual to the mandibular buccal cusps, there is a crossbite on that side. Similarly, anteriorly, the maxillary teeth should extend anterior to the mandibular teeth, which is defined as a normal overjet. The maxillary incisors should overlap the mandibular incisors vertically, which is defined as a normal overbite (Fig. 23-8).³²

Figure 23-8. Overbite is the vertical overlap of the maxillary incisors over the mandibular incisors. Overjet indicates the horizontal extension anteriorly of the maxillary incisors forward of the mandibular incisors.

(Redrawn from Bailey BJ. Head & Neck Surgery—Otolaryngology. 2nd ed. Philadelphia: Lippincott-Raven; 1998.)

Physical Examination

While the CT scan has become the workhorse of maxillofacial trauma diagnosis, there are still important aspects of facial injuries that are best assessed by performing a good physical examination. The importance of this sometimes lost art must be emphasized.

First and foremost, the initial assessment must address the ABCs and any other potentially life-threatening injuries. Facial trauma may be associated with primary airway injuries to the larynx or trachea, or the airway may be secondarily obstructed by swelling of the oral cavity and/or pharynx or by blood. Establishing a safe airway may require intubation or tracheotomy, and the status of the cervical spine must always be considered. When bleeding is not severe, use of a fiberoptic endoscope may allow intubation without manipulation (extension) of the neck. Other options include use of the lighted stylet and retrograde intubation, or temporary airway stabilization using the laryngeal mask airway. When necessary, a cricothyroidotomy may be performed, although if possible, a tracheotomy is preferred.

Most severe bleeding is from the nose and sinuses and can be managed by tamponade with packing. However, laceration of the internal carotid artery in the skull base may require immediate angiography and balloon occlusion above and below the tear, although these injuries are rarely compatible with survival. Of course, neurologic injuries should be evaluated by the neurosurgeons, because these may be life threatening as well.

Although the injury may not be not be life threatening, visual status should be evaluated as soon as possible, because progressive loss of vision usually indicates increasing intraorbital pressure or optic nerve injury, and early intervention is needed to salvage vision.

The quality of the physical examination of the facial structures varies depending on the amount of time that has transpired since the injury, the amount of swelling that has developed, the presence of hematoma, and the presence of treatment-related devices such as packing, tubes, and cervical collars. The general facial appearance should be assessed first, looking for penetrating injuries and lacerations as well as the possibility of foreign bodies. Facial nerve function should be evaluated in each division, and the possibility of cerebrospinal fluid (CSF) leakage, otorrhea, and/or rhinorrhea, should be considered if there is any fluid discharge. If the patient can cooperate, a thorough evaluation of cranial nerve function should be performed. When lacerations are present, sterile examination of the wound may yield information about the status of the underlying bone. In particularly severe injuries, for example, brain herniation through the wound, this should be deferred to surgery.

Middle Third

As noted earlier, the middle third of the face houses numerous structures. Of these structures, the eyes are the most important functionally. Vision should be assessed as soon as possible, because progressive visual loss demands emergency management. A light shined in the eye will evaluate pupillary response, even in the unresponsive patient. Failure of the pupil to respond can indicate injury to the afferent system (optic nerve) or efferent system (third cranial nerve and/or ciliary ganglion), or it could indicate a more serious intracranial condition. This must be immediately evaluated by both the neurosurgeon and the ophthalmologist. A CT scan is imperative to assess the nature and extent of injuries. Other significant but less serious dysfunctions include gaze limitation with or without diplopia. Forced duction testing is performed by anesthetizing the conjunctiva and then manually manipulating the globe in all directions with forceps. An applantation tonometer can also be used to determine whether there is an increase in pressure when the patient looks in the direction of gaze limitation (an increase in pressure of 4 mm Hg or more is indicative of entrapment).³³ The position of the globe should be assessed both in its anteroposterior position (enophthalmos vs. proptosis) and its vertical position. The Hertel exophthalmometer is a good tool for measuring globe position when the lateral orbital rims are not displaced. Otherwise, devices that measure relative to the external auditory canal should be used (e.g., Naugle device).³⁴ Enophthalmos may also be identified clinically, either by recognizing the more posterior position of the globe or sometimes by the deepening of the upper lid crease and elongation of the upper lid. Schubert recommends measuring the anteroposterior distance from the globe to the upper brow with the patient in the supine position, because the distance increases in the presence of enophthalmos.³⁵ Chemosis and subconjunctival hemorrhage as well as periorbital ecchymosis are telltale signs of orbital injury. Although not universally accepted, regardless of the findings, if a periorbital fracture is identified, I believe that ophthalmologic evaluation should be performed before repair, because subtle injuries such as retinal tears may be a contraindication for surgery.

Zygomatic malposition may be visible or palpable, although if there is a large amount of swelling present, it may be obscured. The same is true of nasal fractures. The nasal septum must be visualized, because septal hematomas must be drained before they result in necrosis of the septal cartilage. A careful nasal examination may also reveal trauma to the upper lateral cartilage with resultant loss of nasal valve support. Cheek and lateral nasal numbness (V2 injury) may be the only indication of the zygomatic fracture and should alert the clinician to obtain a CT scan.

Telescoping fractures of the nasal, lacrimal, and ethmoid bones (so-called NEC or NOE fractures) require careful evaluation of the medial canthal relationships, and even with close study, they can still be missed. When the canthal ligament is fully avulsed (which is uncommon) or when the bone to which it attaches is completely detached (more common), the medial canthal ligament gets slowly pulled away from its natural position. It tends to displace laterally, anteriorly, and inferiorly, although the displacement may take place gradually and be missed during the acute phase. Careful assessment includes measurement of the horizontal palpebral widths and the intercanthal distance, as well as the distance between the nasal dorsal midline and each medial canthus. The two sides should be equal, and the intercanthal distance should be approximately equal to each horizontal palpebral width, both of which should be equal. It has also been described as one-half the interpupillary distance (Fig. 23-9).³⁶ A loss of nasal dorsal height and development of epicanthal folds are other telltale signs. Finally, direct traction on the medial canthi should be performed to test the firmness of the attachment. A bimanual examination performed with an instrument in the nose and a finger over the medial canthal area as advocated by Paskert and Manson³⁷ may also be attempted. Evaluation of the lacrimal collecting system is generally reserved for surgery.

Figure 23-9. Metric relationship of normal and abnormal intercanthal distances to interpupillary distance in traumatic telecanthus.

(Redrawn from Holt JE, Holt GR. Ocular and Orbital Trauma. Washington, DC: American Academy of Otolaryngology-Head and Neck Surgery Foundation, Inc., 1983.)

Displaced or mobile fractures of the maxillae are generally assessed at the level of the dentition. A change in the patient’s preinjury occlusion is indicative of a fracture in one or more of the tooth-bearing bones. Of course, evaluation starts at the teeth themselves, which if displaced will alter the occlusion. Excluding loose teeth, the teeth are carefully evaluated for mobility of the alveolar segments to which they are attached. Motion of an entire midfacial segment indicates midfacial fracture, most of which occurs at the maxillary level, even when more superior fractures are present. Pure craniofacial separation at the Le Fort III level in the absence of lower midfacial (maxillary) fractures is an extremely rare occurrence. More important than identifying the level of a midfacial fracture on clinical examination is finding evidence of its presence, which indicates the need for repair as well as careful study of the CT scan to identify all levels involved. Generally, if the teeth and alveoli are intact, grasping the maxilla at or above the incisors and gently rocking back and forth will identify motion relative to either the nasal root or the skull above it. Note that the absence of motion does not assure that the bones are not fractured, because impacted segments may not be mobile. The presence of an anterior open bite is also suspicious, even though subcondylar mandible fractures may produce the same finding. Examination of the palate may also reveal evidence of fracture, and it is not uncommon to find mucosal tears along the paths of palatal fractures.

Radiographic Evaluation

With some exceptions, the CT scan has replaced other forms of radiographic imaging for the assessment of craniomaxillofacial injuries. With the high availability of modern high-speed, high-resolution CT scanners, most maxillofacial trauma surgeons have abandoned plain radiographic imaging of middle and upper third facial bones, even as a screening tool. The numerous overlapping shadows make it easy to miss fractures that would be found on a CT scan, and the presence of a fracture would necessitate a CT scan. The exception here is for simple nasal fractures (simple meaning without evidence of involvement of other facial bones) that are routinely assessed using plain radiographic study (although even these may be unnecessary, in that they have little impact on management). Another exception is the use of the 6-foot AP Caldwell view for creation of a template for use in creating an osteoplastic frontal sinus bone flap.

In general, the plane of the CT (axial vs. coronal) does make a difference in how effectively selected fractures are visualized.^38,39 In a series of studies, fractures were created in fresh cadaveric heads, and these were scanned using various protocols. Dissections were then carried out to correlate the CT findings and to determine which planes of orientation yielded not only the best primary CT data but also the best three-dimensional reconstructions. It was found that axial orientation was best for visualizing most frontal fractures as well as NOE fractures and the zygomatic arches and vertical orbital walls. Coronal orientation was better for the orbital roofs and floors and the pterygoid plates. In general, as would be predicted, vertical structures were better seen on axial scans and horizontal structures were better seen on coronal scans. It was also found that scans performed at a resolution of less than 1.5 mm should not be used to make three-dimensional reconstructions, because the “fill-in” algorithms used by the computer programs created too many misrepresentations. In general, three-dimensional reconstructions create an overview picture that may help the surgeon visualize the overall facial architecture; however, they contain potential inaccuracies that are not present in directly obtained scans.

Upper Third

For frontal fractures, a high-resolution axial CT gives good information about the anterior and posterior walls (Fig. 23-10). However, in the presence of posterior wall fractures, it is impossible to determine the significance of soft tissue density inside the sinuses. When the posterior wall is displaced (regardless of the degree of displacement), and there is soft tissue density within the sinus, I recommend that the inside of the sinus be visualized (either directly or endoscopically). (We have had more than one experience in which placement of an endoscope in a sinus with minimal displacement of the posterior wall and no CSF leakage revealed brain tissue herniating into the sinus.) Displaced anterior wall fractures that require repair are commonly found on CT, even when there is no clinical evidence of cosmetic deformity. Fractures extending into the floor of the anterior fossa are best evaluated with a high-resolution CT scan.

Figure 23-10. Axial computed tomography scan demonstrates markedly displaced anterior and posterior walls of the frontal sinus.

Middle Third

Simple orbital floor blowout fractures are best assessed via coronal CT scanning. However, if there is suggestion of extension into the medial wall, an axial scan (or a high-quality reconstruction from a 1.0 or 1.5 mm coronal) should be obtained as well (Fig. 23-11). In addition, for accurate orbital assessment, Schubert³⁵ has recommended creating a parasagittal reconstruction in the plane of the optic nerve (which actually traverses the orbit from posteromedial to anterolateral, so it is not in a true sagittal plane).

Figure 23-11. A, A coronal scan clearly demonstrating a complete blowout fracture of the right orbital floor. B, An axial scan demonstrating a medial orbital blowout fracture.

Accurate assessment of orbital wall displacement allows the surgeon to anticipate the amount of enophthalmos that is likely to result if the fractures are not repaired.^40–42 This not only helps determine the extent of orbital repair that will be necessary but also whether repair is required at all. CT evaluation of the optic canal and orbital apex take on critical significance in the presence of cranial neuropathies related to these areas. Visual loss due to trauma necessitates immediate analysis of orbital CT scans when possible, because a reversible injury causing constriction of the orbital apex may be identified.^25,26

Whereas zygomatic fractures can be visualized on plain films, accurate assessment of displacement is best analyzed on CT scans. The status of the arch can be evaluated on plain films (so-called bucket-handle views). Although this may be adequate for simple zygomatic arch fractures (without involvement of the malar portion of the zygoma), most zygomatic fractures involve complex three-dimensional alterations in position as well as involvement of the lateral and inferior orbital walls and are best assessed with CT scans. The axial CT demonstrates shifts in the position of the zygomatic arch that may be otherwise missed in high-impact trauma in the anteroposterior direction. Careful comparison with the contralateral arch is important, as is a familiarity with the normal shape of the zygomatic arch, which is more flattened anteriorly and does not therefore represent a true convex arch.

Displacement of maxillary fractures is typically well demonstrated on axial scans. These scans also show fractures through the pterygoid plates, which help define the presence of Le Fort type fractures. However, the horizontal components of these fractures are best displayed on coronal scans (and as might be expected on three-dimensional reconstructions from the coronal scans).⁴³

Upper Face

In the frontal area, classification schemes have focused on the involvement of the frontal sinuses, and these systems have been treatment oriented. The most useful classification, which predicts the likelihood of disruption of the frontal sinus drainage passages, was presented by Stanley and Becker.⁴⁸ They separated frontal sinus fractures into linear horizontal and linear vertical and comminuted anterior and posterior walls, with and without NEC or supraorbital rim fractures. Of interest was the finding that whenever an NEC or a supraorbital rim fracture occurred in combination with comminuted fractures of either the anterior or posterior frontal sinus walls, a ductal injury was predicted. This scheme has been modified by Gonty and colleagues,⁴⁹ but interestingly, in the commentary on this paper written by Stanley,⁵⁰ he suggests that even his own classification system is not all that useful clinically. Numerous other classification systems have been suggested, but they offer little to the planning of the treatment approach.

There are also classification schema designed to predict the incidence of CSF rhinorrhea after anterior skull base trauma. The most useful of these, which is also somewhat intuitively predictable, was reported by Sakas and colleagues,⁵¹ who found that the more centrally located the fracture in the skull base and the more severe the fracture, the greater the likelihood of CSF leakage.

Middle Third

Numerous classification systems have been created for addressing the multiple fractures that occur in this area. Although not always applicable, the most important system is that developed more than 100 years ago by Rene Le Fort.⁵² It was developed artificially by analyzing the facial fracture patterns that were seen in cadavers that were traumatized by being dropped from a height. The Le Fort I fracture, or horizontal maxillary fracture, occurs above the level of the maxillary dentition, separating the alveoli and teeth from the remaining craniofacial skeleton. It crosses the nasal septum, and posteriorly it completes the fractures through the posterior maxillary walls and pterygoid plates. The Le Fort II fracture, or pyramidal fracture, starts on one side at the zygomaticomaxillary buttress, crosses the face in a superomedial direction, fracturing the inferior orbital rim and orbital floor, traverses the medial orbit, crosses the midline at the nasal root or through the nasal bones, and then travels inferolaterally across the contralateral side of the facial skeleton, creating a pyramidal shaped inferior facial segment that is separated from the remaining craniofacial skeleton. Like the Le Fort I, it fractures the nasal septum, the posterior maxillary walls, and the pterygoid plates. The Le Fort III fracture, or complete craniofacial separation, occurs at the level of the skull base, separating the zygomas from the temporal bones and frontal bones, crossing the lateral orbits and medial orbits, and reaching the midline at the nasofrontal junction, also violating the nasal septum and pterygoid plates (Fig. 23-12). Even though many fractures seen clinically do not fit precisely into this classification scheme, it has stood the test of time, and it does prove useful for communication and treatment planning. In order to use it for documentation purposes, it is helpful to more specifically describe the nature of the particular fractures in each case. For example, the pure Le Fort III fracture is probably a rare occurrence, yet many surgeons will describe an injury by the most severe level encountered and then describe the additional components.

Figure 23-12. Le Fort I fracture is a horizontal fracture that separates the bone containing the maxillary dentition from the remainder of the craniofacial skeleton. The Le Fort II fracture is a “parametal” fracture, which extends across the maxilla through the infraorbital rim and orbital floor up through the medial orbital wall and across the nasal root area and then across similarly the other side. The Le Fort III fracture is the true craniofacial separation, which includes fractures of the zygomatic arches and frontozygomatic areas, then crosses the lateral inferior and medial orbits, and is completed across the nasal root. Note that all Le Fort fractures cross the nasal septum and pterygoid plates.

Numerous classification schemes have been used to describe NOE fractures. The system that is probably the most useful for treatment planning is that described by Markowitz and colleagues (Fig. 23-13).⁵³ In this scheme, a type I fracture occurs when a large central fragment containing the medial canthal ligament is freed from the surrounding bone. It is repaired by rigidly fixing this central fragment in place. In a type II fracture, there is significant comminution, but the fragment containing the medial canthal ligament is still repairable. However, transnasal fixation of this fragment and/or the tendon is still necessary. In type III injuries, the tendon is either detached or attached to an unusable fragment. It must be freed and directly repaired with transnasal fixation. This description shows how a useful classification not only describes the injury but also helps in the planning of the repair.

Figure 23-13. Naso-orbital ethmoid fractures have been classified as type I, type II, and type III by Markowitz and colleagues.⁵³ The type I fractures (A) include a solid central segment to which the medial canthus is attached. Type II injuries (B) are more comminuted than type I but still leave a central segment to which the medial canthus is intact. In type III injuries (C), the bone is shattered and there is no solid bone to which the medial canthal tendon is attached.

(Redrawn from Markowitz BL, Manson PN, Sargent L, et al. Management of the medial canthal tendon in nasoethmoid orbital fractures: the importance of the central fragment in classification and treatment. Plast Reconstr Surg. 1991;87:843.)

Lower Third

Mandibular fractures are for the most part classified by the anatomic region in which they occur and by their severity. Severity typically includes simple, comminuted, or avulsive (bone loss). The mandible is also categorized as dentulous, edentulous, or atrophic edentulous. Historically, a common classification has separated so-called favorable from unfavorable fractures. In fact, these descriptions are no longer considered helpful in determining the treatment plan, and they certainly offer no documentation or communication advantages. They are thus of historical significance only.

General

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