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Medical imaging of facial and mandibular fractures.

Man's face is his single most distinguishing physical characteristic. It is at once key to his identity and his primal means of communicating both thought and emotion.[1]

--Richard Carlton Schultz, M.D., FACS

Mandibular and facial fractures are among the most frequently seen injuries in the radiology department. The most common cause of facial fractures are automobile or motorcycle accidents, followed by injuries in the home and sports injuries.

In automobile accidents, the front-seat passenger is most at risk for facial injury, and the most common source of facial injuries during automobile accidents is the windshield. At speeds lower than 20 miles per hour, the potential for facial injuries as the result of an automobile crash can almost be eliminated with the use of a shoulder-lap seat belt. At speeds greater than 20 miles per hour, the use of airbags is essential to minimize or prevent head trauma.[1]

Motorcycle accidents also are a leading cause of facial fractures. The majority of those injured in motorcycle accidents are young men, who often sustain multiple severe facial fractures as a result of being thrown headfirst over the handlebars. Wearing a properly fitted helmet can reduce the potential for injury.[1]

Accidents occurring in and near the home are another source of facial fractures. Severe facial injuries can and do occur in the home with a relatively high frequency. They often are the result of a fall, push or being struck by a projectile object. Injuries in the home also may be the result of a freak accident such as a falling object.[1]

Sports injuries to the face generally tend to be relatively minor in severity, consisting for the most part of abrasions, contusions and lacerations. Facial fractures generally are the result of direct blows sustained during contact sports, such as being hit in the face by the backward swing of a baseball bat. These types of fractures are commonly associated with burst-type, soft tissue injuries. They sometimes are seen over the supraorbital ridge and zygoma.[1]

Other, less common, causes of facial fractures include animal bites, fist fights or gunshot wounds.[1]

A comprehensive understanding of facial anatomy and function is critical when imaging, diagnosing and treating a patient with facial trauma. Training and experience in trauma care also are important in determining the outcome.

Care of any trauma patient can be divided into several stages: pre-hospital, initial assessment and resuscitation, secondary evaluation and diagnosis, treatment and rehabilitation.[2] In addition, when facial injuries are involved, restoration of facial appearance and function is paramount.

Trauma to the face falls into two categories: soft tissue injury and injury to the bone. This article concentrates on injuries to bone.[1]

Initial Stabilization

Upon presentation, the patient with facial injuries must be stabilized. The first step is to be sure the airway is unobstructed by blood, vomit, collapsed mandibular fractures or hematomas related to the injury. Most of these obstructions can be cleared quickly by sweeping a finger deep into the mouth and oral pharynx. A finger is the quickest way to clear an obstructed airway. Fractures of the larynx or trachea require immediate attention, but the airway must be cleared first.[3-5]

Airway problems often are corrected by having the patient sit up straight, if this is possible. Patients with facial injuries may struggle to sit up or attempt to thrust their head forward. This motion is a protective reflex by the patient to clear his or her airway. It is important to note, however, that in patients who have sustained severe facial injuries, forcing the patient to remain in a supine position can result in death.[3-8]

While most facial injuries are associated with substantial bleeding, the hemorrhaging itself is rarely sufficient to cause systemic shock. Extensive bleeding from facial wounds often is the result of injury to the external maxillary artery, the superficial temporal artery or the angular artery, which almost always can be controlled by direct pressure. The most dangerous complication of facial bleeding is the potential for airway obstruction. Swallowing large amounts of blood can cause gastric upset and lead to vomiting, possibly resulting in aspiration or airway obstruction.[1,3-9]

Shock

Shock is rarely caused by facial injury alone. Furthermore, even extensive facial injuries seldom cause great pain. Therefore, when a patient with facial injuries is in shock, the possibility of underlying injuries should be investigated as the cause. When treating shock after trauma it is important to determine and attempt to correct the cause. It is important to support the patient by controlling pain, conserving body heat, controlling fear and apprehension and re-establishing intravascular fluid volume.[1,3-9]

In addition to treating shock, it is important to ascertain the presence of any associated injuries. Although patients rarely die from facial injuries alone, they may die from associated injuries. Therefore, it is important to evaluate the status of possible cardiopulmonary, gastrointestinal and neurological injuries. Only after the patient's condition has been stabilized should facial injuries be evaluated and treated.[1,3-9]

Facial Anatomy

Traditionally, the human face is divided into thirds (or zones): the upper, middle and lower thirds.[1,6] (See Fig. 1.) Within each of these three regions of the face are several potential sites of fracture, including fracture of specific bones and multiple fractures of one particular bone.

[Figure 1 ILLUSTRATION OMITTED]

For the most part, bones of the human face are thin and unsupported, forming a compressible shield designed to protect and insulate the eyes, brain, pharynx and other structures. As such, it is important to be cognizant of the potential effects of facial trauma on these vital structures.[1,2,6]

When evaluating injuries to the bones of the face, it is important to determine the type of fracture and to pinpoint the location(s) of fracture(s). Therefore, a comprehensive understanding of facial anatomy is essential.

Upper Third of the Face

The upper third of the face consists of the frontal bone, the temporal bone, the frontal sinuses or glabella, the supraorbital ridge and the roof of the orbits. Glabellar and supraorbital fractures are rare, but they often result in serious injuries. They are usually the result of automobile or motorcycle accidents, and they may be associated with injury to the brain.[1,6,10]

* Frontal sinuses. The frontal sinuses, which comprise the glabella prominence, are thin-walled, air-filled structures. Because the frontal sinuses are midline structures with a much more prominent structure (the nose) nearby, they rarely are fractured. As such, when glabella fractures do occur, they are highly correlated with the presence of nasal fractures.[1,6,10]

It is important to note that although the frontal sinuses are resilient and resistant to fracture, fractures can and do occur. When deep fractures of the frontal sinuses occur, the outcome is quite serious. In cases of deep fracture and glabellar depression, the bone often is smashed into tiny pieces, like a crushed egg shell, possibly resulting in additional damage to the ethmoid bone, dura mater and the brain.[1,6,10]

* Supraorbital ridge. The supraorbital ridge is a massive, well-supported structure. Fractures to the supraorbital ridge are not common and must be caused by massive forces or a direct blow that is concentrated over a small area. They often occur as the result of a motorcycle accident or as the result of direct, concentrated blunt trauma, like that experienced when an individual is struck in the face by a baseball bat swung at full force. Although they are not common, fractures of the supraorbital ridge tend to occur in tandem with fractures to the frontal sinuses.[1,6,10]

Supraorbital fractures are characterized by the presence of a flattened brow; displacement of orbital contents; numbness of the forehead; and lacerations, swelling and bruising of the forehead and eyebrows. Because supraorbital fractures are the result of concentrated force, multiple, small bone fragments often are found firmly impacted deep in the orbits. Large bone fragments also may occur, and it is important that these fragments are documented radiographically to prevent tearing in the orbital wall.[1,6,10]

* Orbital roof. Fractures of the orbital roof can occur alone or in conjunction with fractures of the frontal bone or zygomatic complex. Fractures of this type can be dangerous because they can result in subdural hematoma, brain abscess and other types of brain injury.[1,6,10,11]

* Frontal bone. Fractures of the frontal bone can be depressed or linear in nature and often are associated with fractures of the orbit. Fractures of the frontal bone in association with the orbit usually can be treated with wires or bone grafts. However, other fractures of the frontal bone may require neurologic examination because brain injury and cerebral edema are common. 1,6,10 (See Fig. 2.)

[Figure 2 ILLUSTRATION OMITTED]

Middle Third of the Face

The midface contains the orbits, maxilla and zygoma and the lacrimal, nasal, palatine, inferior nasal concha and vomer bones.[1,6,10] While the sphenoid, frontal and ethmoid bones are not typically considered facial bones, they are often injured in midfacial fractures and can be considered part of the midface as well. The middle third of the face begins inferior to the frontozygomatic suture laterally and contains numerous cavities and sinuses that are reinforced horizontally and vertically by bony struts or buttresses.[12-20]

Fractures of this portion of the face are the most difficult to diagnose and treat, due to the large number of small bones and articulations present in this region. The bones in this area of the face are relatively thin and oriented in many planes, further complicating accurate diagnosis. Because this part of the face is buttressed by dense cranial bones, even severe fractures may be difficult to discern radiographically. The midface is important in terms of function and structure as well as physical appearance. As such, the diagnosis of injury to the midface must be undertaken carefully and comprehensively.[12-20]

As might be expected, the more prominent bones of the face, such as the zygoma and nose, are more likely to be injured. Data indicate that the nose is injured most frequently, followed by injury to the cheek bone. Injury of the cheek bone also is commonly associated with fracturing of the orbits. Fractures of the zygomatic arch, the portion of bone located posteriorly to the zygoma, often are an extension of a fracture to the zygoma, although fractures of the zygomatic arch may occur independently.[12-20]

* Maxilla. The maxilla is formed by fusion of the two bones of the upper jaw. (See Fig. 3.) The body of the maxilla is hollow and contains the maxillary sinus. The anterior wall of the nasal sinus is the facial surface of the maxilla, and it is quite thin. The medial wall is the lateral nasal wall. The sinus opens superiorly and medially into the nasal cavity. The superior wall of the sinus is the orbital floor, and the floor of the maxillary sinus is comprised of the palatine and alveolar processes of the maxilla.[1,6,14-24]

[Figure 3 ILLUSTRATION OMITTED]

The frontal process of the maxilla articulates with the frontal bone to form the medial orbital rim. The medial portion of the frontal process fuses with the nasal bone and is also called the nasofrontal process. Posteriorly, this process articulates with the lacrimal bone to form the anterior portion of the medial orbital wall. The area of articulation between the frontal bone, nasal bone and lacrimal bone is prominent in the facial skeleton and frequently is fractured as the result of blunt trauma.[1,6,14-24]

The alveolar process extends inferiorly from the maxilla and contains the maxillary teeth. Teeth are important in the management of many midfacial fractures. The alveolar process may be fractured by direct trauma and may become functionally separate from the maxilla.[1,7,12-22]

* Palatine process. The palatine process is a horizontal process that arises from the lower portion of the medial surface of the body of the maxilla. It joins the process of the other side and forms the bulk of the hard palate.[1,6,14-24]

* Zygomatic process. The zygomatic process of the maxilla arises from the anterolateral corner of the maxilla and articulates with the zygoma. Together they form the inferior orbital rim and comprise the majority of the orbital floor.[1,6,14-24]

* Zygoma. The zygoma, or malar, bone is a paired bone comprising the cheek. The zygoma is a thick, diamond-shaped bone, comprised of four processes that form the lateral and anterior projections to the midface. The frontal process forms the lateral orbital wall and articulates with the frontal bone at the frontozygomatic suture. This articulation may be separated or rotated in isolated zygomatic fractures. The temporal process forms the zygomatic arch and articulates with the temporal bone. The maxillary process articulates with the maxilla to form the infraorbital rim and a portion of the floor of the orbit. The remaining process articulates with the maxilla on the lateral wall and forms the zygomatic eminence.[1,2,10,14,15,17,18,25-32]

* Nasal bones. The rectangular-shaped nasal bones articulate superiorly with the frontal bone and with each other in the midline. The nasal bones articulate posteriorly with the frontal process of the maxilla. Although the nasal bones are relatively thick superiorly, they are thinner inferiorly, which is where most fractures tend to occur.[6,10,14-18]

* Ethmoid bone. The ethmoid bone is central to the face and is an integral part of the nasal structure, both orbits and the anterior cranial base. The vomer is located in the midline of the nasal fossa and forms the posterior aspect of the nasal septum. A plow-shaped bone, it articulates with the palatine, maxillary and ethmoid bones, but it is rarely a major concern in the management of facial trauma.[6,10,14-18]

* Palatine bones. The palatine bones attach the maxilla to the sphenoid bone. They consist of a horizontal portion and perpendicular plates. The horizontal portion articulates with the maxilla anteriorly and with the palatine bone of the opposite side in the midline to form the posterior portion of the hard palate.[6,10,14,15,17,29]

* Frontal bone. Technically, the frontal bone is not part of the midface; rather, it is a cranial bone forming the anterior aspect of the skull cap. However, its importance in the discussion of facial fractures becomes obvious when considering the numerous ways in which the frontal bone articulates with various bones of the midface. For example, the frontal bone articulates with the zygoma, maxilla and nasal bones. It also articulates with the ethmoid bone, the lacrimal bones and the sphenoid bone. In addition, the frontal bone forms a large portion of the superior aspect of the orbit, articulating with the zygoma at the frontozygomatic suture to form the lateral aspects of the orbital walls. The thickened portion of the frontal bone superior to the orbits forms the supraorbital ridges. The frontal sinus is located in the frontal bone superiorly to the nasal bones. (It is interesting to note that the frontal sinuses of about 4% of the population cannot be visualized radiographically.[1]) The frontal sinuses are protected by the supraorbital ridges, areas of high resistance in comparison to the anterior wall of the sinus itself.[6,10,14-18]

* Sphenoid bone. The sphenoid bone is a single bone located in the midline at the base of the skull, forming the cranial bases anteriorly and superiorly where it joins the parietal and frontal bones to complete the cranial complex. It is hollow; forming two cavities separated by a thin septum. The cavities are called sphenoid sinuses.[6,10,14-18] (See Fig. 4.)

[Figure 4 ILLUSTRATION OMITTED]

Lower Third of the Face (The Mandible)

The lower third of the face consists primarily of the mandible, which includes the mandibular condyles and coronoid processes. (See Fig. 5.) Although the mandible is the largest and strongest facial bone, it is commonly fractured in cases of maxillofacial trauma. In fact, mandibular fractures are twice as common as midface fractures, despite the fact that almost four times as much force is required to fracture the mandible as the maxilla.[1] Muscle attachment, bone structure and dentition play roles in the processes of mandibular fracture, and certain types of fractures are more commonly seen in particular regions of the mandible.[6,10,14-18]

[Figure 5 ILLUSTRATION OMITTED]

The mandible is comprised of a U-shaped body and two rami. The angle formed between the body and ramus ranges between 110 [degrees] and 140 [degrees], averaging 125 [degrees]. This angle decreases during growth, but becomes more obtuse with aging. The body of the mandible supports the alveolus and the lower dentition. The ramus of the mandible is quadrilateral in shape and taller than it is wide. The lateral aspect of the ramus may be rough in texture as a function of the attachment of the masseter muscle. The medial surface is characterized by the presence of the mandibular foramen. The mandibular notch is located on the superior aspect of the ramus, bordered by the coronoid process anteriorly and the condylar process posteriorly.[6,10,14-16,33,34]

Due to its shape, substantial forces are created at the angle of the mandible. Bone height is important in determining the strength of this bone in addition to the presence of the masseter and medial pterygoid muscles. The normal aging process, with its potential for bone resorption, tends to weaken this area. Other areas of weakness include the mental foramen, the mandibular angle and the condylar neck. If unerupted or impacted teeth are present, the tooth socket also is an area of weakness. Fortunately, however, the disadvantage of unerupted teeth in children actually is counteracted to a large extent by the flexibility and resiliency of bone in children.[6,10,14-16,33,34]

The most common sites of mandibular fracture are the condyles; the mandibular angle, particularly in the presence of unerupted or impacted third molars; the mental foramen or body, the mandibular parasymphysis; and any aspect of the dental alveolus. Because of its U-shape, fractures of the mandible often are bilateral, creating one fracture at the site of the injury and another contralaterally. As such, mandibular fractures often involve multiple sites, and the presence of a fracture in one area does not rule out the possibility of other fractures. It also has been shown that the mandible is more sensitive to lateral impacts than frontal impacts.[1,6,10,14-16,33,34] Mandibular fractures commonly are described on the basis of their location within the mandible. The presence or absence of teeth also is important in describing mandibular fractures:

* A Class I fracture refers to a fractured mandible with teeth on both sides of the fracture.

* A Class II fracture describes a fracture in a partially edentulous mandible in which the remaining natural teeth are present on only one side of the fractured mandible.

* A Class III fracture occurs in the fully edentulous mandible.[1,6,10,14-16,33,34]

Identifying Characteristic Fractures

When dealing with any type of bone injury, it is important to determine the location(s) and the type(s) of fracture. In particular, proper identification of the type of fracture is crucial in determining a successful treatment plan.

Types of Fractures

Like all fractures, facial fractures are classified according to their characteristics and location. (See Table 1.) The types of facial fractures are: closed (simple), open (compound), greenstick, comminuted, undisplaced and displaced. Each is discussed individually below.[1,3,4,6]

Table 1 Classification of Facial Bone Fractures[1]

Type

Closed (simple)

Open (compound)

Greenstick

Comminuted

Undisplaced

Displaced Location

Upper Third of Face

Frontal sinuses (glabella)

Supraorbital ridge

Frontal bone

Middle Third of Face

Nasal bones and septum

Naso-orbital area

Zygoma

Zygomatic arch

Orbital floor

Maxilla

Transverse (Le Fort I)

Pyramidal (Le Fort II)

Craniofacial disjunction (Le Fort III)

Lower third of face (mandible)

Alveolar process

Symphysis

Body

Angle

Ascending ramus

Coronoid process

Condyle

Temporomandibular joint region

* Closed (simple). To distinguish between a closed and open fracture, the status of the skin and mucus membrane, when appropriate, must be considered. Simple fractures are fractures in which the skin had not been broken.[1,3,4,6]

* Open (compound). Compound fractures are injuries in which an external wound consisting of a break in the skin, mucosa or periodontal membrane comes in contact with a fractured bone.[1,3,4,6]

* Greenstick. A greenstick fracture is one in which one side of the bone is broken and the other side is bent, like a tree branch that has splintered.[1,3,4,6]

* Comminuted. A fracture in which the bone is splintered or crushed in many small pieces is known as a comminuted fracture. This type of facial fracture is common due to the thin nature of facial bones. It often is seen in the nasal bones, orbits, frontal and maxillary sinuses, and the body of the mandible.[1,3,4,6]

* Undisplaced. This type of facial fracture often requires no treatment beyond observation. However, while radiographic findings may indicate no displacement of the injured bone, clinical examination may reveal displacement. This is common with fractures of the nose, in which swelling may mask displacement.[1,3,4,6]

* Displaced. Displaced fractures should be reduced. Displacement may not be obvious until swelling has resolved. Fractures of the nose, cheekbone and floors of the orbits are particularly susceptible to this phenomenon. In cases in which displacement is not apparent, it is important to continue to monitor these structures as edema is resorbed in order to detect any displacement as soon as possible.[1,3,4,6]

Preliminary Diagnosis of Facial Injuries

Observation

Once the trauma victim has been stabilized, initial diagnosis of facial injuries often can be accomplished by observation and palpation.[1] Observation of facial damage begins with soft tissue damage. The patient's eyes should be opened to view any obvious ocular injury. Although the human face is not truly symmetrical, it is important to evaluate facial symmetry. Facial asymmetry related to trauma often is apparent, and although it may not be associated with pain or obvious injury, it is often indicative of underlying trauma to the face.[1]

Palpation

Palpation can be useful in determining the extent of facial injuries. For example, palpation can elicit tenderness that may be indicative of a fracture. When confronted with facial injury, the pattern of palpation is as follows: supraorbital and lateral orbital rims, infraorbital rims, malar eminences, zygomatic arches, nasal bones, maxilla and mandible. As discussed previously, certain fractures may be difficult to discern because of swelling or bruising, and may appear as negative findings upon radiographic examination. As the swelling begins to resolve, palpation can detect subtle fractures that might otherwise go undetected.[1]

Radiographic Imaging of Facial Fractures

Radiographic imaging is an important tool in the diagnosis of facial trauma and to detect underlying fractures or other injuries. It is important to identify the presence of fractures and any underlying anatomical changes as early as possible after the event to provide prompt and appropriate treatment.[1,10,45-52]

A variety of diagnostic imaging modalities are available to evaluate facial fractures, each with its own strengths and weaknesses. The two diagnostic examinations most commonly used to image facial trauma are conventional skull radiography and high-resolution computed tomography. In addition, two-dimensional and three-dimensional reconstructions from CT scant can help surgeons in the planning and reconstruction of facial structures damaged as the result of trauma.[1,10,45-52]

Although nuclear medicine imaging techniques are useful in evaluating the status of bone grafts, they are not particularly useful in the diagnosis or evaluation of facial fractures. In addition, neither ultrasound nor magnetic resonance imaging has proven useful in the initial evaluation of facial fractures. However, these techniques may be useful as an adjunct to conventional radiography and CT in the evaluation of soft tissue trauma and intracranial injuries.[1,10,45-52]

Conventional Radiography

The first step in the radiographic evaluation of suspected facial fractures is conventional radiography. In cases of suspected fractures of the facial skeleton, a set of six standard views known as the "facial series" is performed. This series includes the Waters, Caldwell and lateral views of the facial bones. Standard views used to evaluate the mandible include the Towne, oblique and posteroanterior. When necessary, these views may be supplemented by specific mandibular or nasal views.[53-66]

The benefits of each of these standard views is that they can be used to evaluate targeted areas of the skull quickly and relatively inexpensively. Obviously, the quality of the images obtained is contingent upon the radiologic technologist, the equipment, the film and screen, as well as the cooperativeness of the patient.[53-66]

Some of the limitations of conventional radiography in the evaluation of facial fractures is that the images lack soft tissue detail. Ambiguous readings also may occur because of overlapping shadows or the lack of quantitative data. In addition, certain images require that the patient be moved, and these images may be precluded in patients with suspected cervical trauma.[53-66]

In trauma cases, facial radiographs should be taken upright to demonstrate air, blood and fluid levels, unless the patient's condition prohibits upright imaging.

Facial Views

* Waters view. This projection also is referred to the occipitomental view and is considered the best overall view for the orbits, orbital rim structures, orbital floor, maxillary and frontal sinuses, zygomatic arches, nasal arches and septum. (See Fig. 6.) The patient is placed prone and the image is taken with the chin in full contact with the table. The view shows the skull head on. In cases of severe injury, a reverse Waters view is possible with the patient in the supine position.[53-66]

[Figure 6 ILLUSTRATION OMITTED]

* Posteroanterior view (Caldwell view). This projection differs from the Waters in that the patient's neck is flexed so that the forehead rather than the chin is in contact with the examination table. It provides a slightly different view of the calvarium, including the roofs of the orbits, frontal sinuses, nasoethmoid pyramid, nasal septum, ethmoid sinuses and mandible.[53-66] (See Fig. 7.)

[Figure 7 ILLUSTRATION OMITTED]

* Lateral view. In the lateral view, the lateral aspect of the temporal bone is placed in direct contact with the examination table. This projection provides a tangential view of the sinuses and the nasal arch. It provides a profile view of the patient along with the lateral orbital wall, sphenoid sinuses and mandible.[53-66] (See Fig. 8).

[Figure 8 ILLUSTRATION OMITTED]

Mandibular Views

* Frontonuchal view (Towne projection). In this projection the patient is placed in the supine position with the occiput slightly elevated. This view permits excellent visualization of the ascending ramus and the mandibular condyles. It also provides a good view of the zygomatic arches and the lateral walls of the maxillary sinuses.[53-66] (See Fig. 9.)

[Figure 9 ILLUSTRATION OMITTED]

* Oblique views. Oblique views are essential to the evaluation of mandibular fractures. These views demonstrate the horizontal and ascending rami, coronoid processes, molars and necks of the condyles.[53-66] (See Fig. 10.)

[Figure 10 ILLUSTRATION OMITTED]

* Posteroanterior view. This projection provides a frontal view of the body of the mandible, symphysis, rami, occlusal surfaces and the alveolar processes.[53-66] (See Fig. 11.)

[Figure 11 ILLUSTRATION OMITTED]

Supplemental Views

* Lateral and axial (occlusal) views of the nose. These views are used when facial injuries are confined to the nose. They reveal the detail necessary to evaluate fractures in the nasal bones, nasal and frontal processes of the maxilla and the anterior nasal spine.[53-66] (See Fig. 12.)

[Figure 12 ILLUSTRATION OMITTED]

* Submentovertical (Schuller, Pfeiffer) view of the zygomatic arches. This inferosuperior projection is useful for demonstrating the zygomatic arches in silhouette. It also provides a good view of the mandibular angles.[53-66] (See Fig. 13.)

[Figure 13 ILLUSTRATION OMITTED]

* Panoramic view of the mandible. This projection also is referred to as panoramic tomography or rotational tomography. It provides outstanding detail in a single long piece of film, demonstrating a panoramic view of the entire mandible including the horizontal and vertical rami, temporomandibular joints and dental arches.[53-66] (See Fig. 14.)

[Figure 14 ILLUSTRATION OMITTED]

* Tomograms. This is a radiograph in which only one plane remains in focus while all other layers are diffused through linear or curved movement of the x-ray tube and the film cassette. It is useful in the diagnosis of orbital floor defect or in cases in which routine views are ambiguous.[53-66] (See Fig. 15.)

[Figure 15 ILLUSTRATION OMITTED]

* Optic foramina (modified Stenver or Rhese) view. Originally employed to demonstrate the petrous ridges, it is an excellent projection to evaluate the optical foramina. It is used to rule out fracture of the optical foramen in cases of suspected injury to the optical nerve.[53-66] (See Fig. 16.)

[Figure 16 ILLUSTRATION OMITTED]

Computed Tomography

Computed tomography has become the imaging method of choice for the evaluation of facial and mandible fractures. In particular, CT offers a distinct advantage over conventional skull radiography in the diagnosis of facial trauma in patients with suspected cervical spine or intracranial injury.

Computed tomography also is the preferred diagnostic imaging tool for imaging facial injuries in the following circumstances:[61,67,68]

* When there is displacement of the ocular contents.

* When there is comminution of bone or multiple fractures.

* When there is suspected involvement of the thin bones of the orbits and midface.

For the evaluation of facial fractures, high-resolution CT scanning compares favorably with traditional radiography with regard to radiation exposure, patient acceptance, spatial resolution, duration of the examination, convenience and availability.[45-51] The widespread availability of CT scanners has made the evaluation of facial injury and head trauma much more convenient and feasible for patients in whom facial fracturing is suspected. In addition, acceptable images can be obtained with CT in patients with suspected cervical spine injuries and in comatose or intubated patients. [1,45-51]

The axial CT scan used in the evaluation of facial fractures is oriented along the orbitomeatal plane. When evaluating facial fractures, CT scan slices are reduced in size to 2 mm to 3 mm as compared to the 8 mm slices commonly used in brain scanning. The field of view for evaluating facial fractures is likewise reduced from 10 x 10, which is common in brain scanning, to 5 x 5. By reducing the field of view, each pixel represents a fraction of a millimeter of the area being scanned. This is particularly useful when evaluating small structures such as facial bones because the smaller area allows better visualization of these structures.[1,45-51]

In addition, a standard set of axial images using standard 8 mm slices and a 10 x 10 field of view is useful in evaluating intracranial features and can be used in conjunction with the other CT image to evaluate facial fractures and any associated intracranial images. Once the patient has left the scanning area, sequential axial CT scans can be reformatted to create images in other planes.[1,45-51]

Three-Dimensional Imaging

The combination of axial and reformatted scans can help identify tissue destruction; however, bone fragments may be difficult for the viewer to interpret. Three-dimensional surface reconstruction can facilitate the visualization of the skull, identifying deformities. These images can be viewed in any perspective and from any desired plane. In addition, software is now available to separate (or disarticulate) osseous articulations. Furthermore, this functionality can be expanded to view bone fragments independently and from any angle.[12,69]

Three-dimensional surface reconstruction can provide additional information to that obtained from standard CT images. For example, osseous surface reconstruction can accurately visualize the direction and amount of rotation in zygomatic and maxillary disjunction fractures. It is also useful in the evaluation of fractures within the body of the zygoma, which may be misinterpreted as a trimalar fracture with conventional skull radiography.[61,70]

Three-dimensional reconstruction also is useful in the evaluation and repair of calvarial fractures. Previously, open fractures of the skull cap with associated necrosis of brain tissue were treated by the removal of bone fragments and dead tissue. This approach often results in a concave area of the skull with no bone, just scalp, to protect the underlying brain. The advent of 2-D and 3-D reconstruction has been used to circumvent this previously difficult-to-treat condition.[1] (See Fig. 17.)

[Figure 17 ILLUSTRATION OMITTED]

Magnetic Resonance Imaging

Magnetic resonance imaging has not been proven useful in the evaluation of facial fractures due to the dark images of bone and the greater slice thickness when compared with high-resolution CT. However, MRI is useful in the evaluation of optic nerve injuries, intracranial injuries and facial muscle function. This may have particular application in the assessment of the temporomandibular joint space.[12,61,71-75]

Conclusion

Remarkable advances have been made in the diagnosis and treatment of facial fractures. New surgical techniques combined with enhanced diagnostic tools can produce amazing results. The face is an essential component of a person's appearance and sense of being. As such, in cases of trauma to the face it is particularly important that injuries be diagnosed accurately and treated promptly.

Prompt diagnosis is essential to a successful outcome. Once the patient has been stabilized, clinical observation and routine radiographic views are the first line of defense. However, neither method is infallible. When clinical findings do not agree with the radiographic findings, supplemental images may be required.

In addition to radiographic imaging, high-resolution CT scanning can provide information about facial fractures, particularly in cases of suspected cervical trauma or intracranial injury. Three-dimensional reconstruction can be useful in visualizing bone fragments out of context and from all angles and planes. This is useful in the planning and guidance of reconstructive surgery. Furthermore, three-dimensional reconstructions can be used to fashion anatomically exact prostheses, eliminating the need for bone grafts in some patients while producing an aesthetically pleasing result.

References

[1.] Schultz RC. Facial Injuries. 3rd ed. Chicago, Ill: Year Book Medical Publishers; 1980.

[2.] Cook D, Trunkey D. Emergency and intensive care of the trauma patient. In: Fonesca RJ, Walker RV, eds. Oral and Maxillofacial Trauma. Vol. 1. Philadelphia, Pa: WB Saunders; 1991:91-113.

[3.] Shires GT. Care of the Trauma Patient. New York, NY: McGraw-Hill Book Company; 1996.

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Julliana Newman, B.A., ELS, is a certified editor of the life sciences. Her Radiologic Technology article titled "Early Detection Techniques in Breast Cancer Management" recently was awarded the 1997 Rose Kushner Award from the American Medical Writers Association for writing achievement in the field of breast cancer. The award was sponsored by the AMWA and Zeneca Pharmaceuticals. Ms. Newman resides in Albuquerque, N.M.

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Date:May 1, 1998
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