Radiography
Technique
Plain radiographs are usually not ordered in complex trauma cases. The applicable plain images include facial bone series, which typically includes Waters, Stevens, and Townsend views.
Panorex views are the best images for showing the orthognathic relationship and occlusion.
Imaging pearls
- A Panorex view is especially helpful when associated mandible fractures are present.
- If there is concern with the possibility of a midface fracture, a CT scan is warranted.
- Plain radiographs have largely been replaced by CT scans for examining the midface.
Computed Tomography
Coronal CT of a patient with right Le Fort III fracture and left Le Fort II fracture.
Bilateral pterygoid fractures.
Axial picture. Note bilateral pterygoid plate fractures.
Three-dimensional reconstruction of a patient with right Le Fort I fracture and a left Le Fort II fracture.
Coronal CT demonstrating a right Le Fort I fracture and a left Le Fort II fracture.
Technique
The preferred examination begins with a proper evaluation in the emergency department to ensure that the patient is stable and that the appropriate organ systems are treated in the necessary order. The preferred radiologic examination is CT scanning of the facial bones, with coronal and axial sections in bone windows for maximal detail. Midface fractures are best evaluated with CT imaging. Plain radiography and MRI play more limited roles in the evaluation of midfacial fractures.21
The imaging of choice for Le Fort fractures is CT scanning of the midface without contrast enhancement. It is important to analyze the whole face for fractures, including the entire mandible, because of the high rate of fracture of the upper and lower face when midface fractures occur.
The CT scan is analyzed in bone windows; 2- to 3-mm sections are preferred. A single-plane CT scan does not provide as much information as a 2-plane CT scan. It is crucial to use a systematic analysis in analyzing midface fracture CT scans.
Axial sections are best for analyzing the posterior wall of the antrum, the pterygoid plates, the hard palate, dentoalveolar segments, the zygomatic arch and body, and the lateral wall of the orbit. Coronal sections provide the best images for analyzing the anterior wall of the maxilla, the inferior orbital rim, the palate, and the orbital floor.
Reformatted CT images are also of high quality and have been shown to be reliable and accurate in surgical reconstructive efforts.
With the introduction of helical CT, which acquires data in a continuous fashion, it is now possible to produce computer-reformatted images, either coronal or sagittal, from the standard axial images. Coronal images reformatted from helically acquired thin-section axial CT data have been shown to have high sensitivity and specificity in the detection of fractures, as compared with direct coronal imaging.
Three-dimensional (3D) reconstructions are usually not necessary in analyzing midface fractures. However, these reconstructions may be useful in highly complex fractures or secondary reconstructions and in facilitating communication between the radiologist and the surgeon. Cavalanti et al have shown that 3D construction is quantitatively accurate for surgical planning and evaluation.
Three-dimensional reconstruction of a patient with a right Le Fort III fracture and left Le Fort II fracture.
Interpretation
Manson described a classification system in which fractures were classified as resulting from low-, middle-, or high-energy mechanisms; the determination of whether a fracture was the result of a log-, middle-, or high-energy mechanism was made on the basis of the degree of segmentation and displacement seen on CT scans.22 In Manson's system, fractures are classified according to the displacement and the degree of comminution. In type I fractures, there is minimal displacement and no comminution. In type II fractures, there is moderate displacement and a small amount of comminution. In type III fractures, there is severe displacement, with the major buttresses comminuted in multiple locations. This system may serve as a dependable guide for determining the prognosis and proper intervention.
In making the radiologic report, it is important that damage to adjacent structures, such as the nasolacrimal duct, mandible, zygoma, and orbit, be commented upon. The degree of displacement and the degree of comminution may affect the surgical approach. The presence of any hardware may signify previous traumatic injury and repair.23,24,25
Accuracy
CT scanning is the criterion standard for detecting facial fractures. It is superior to clinical examination, and it is more than 95% accurate.
Sagittal reformatted helical CT scans are comparable in quality to direct sagittal scans.
CT scanning of a facial bone results in few false-positive or false-negative results.
Koltai et al (1999) applied Manson's energy classification with CT scanning in children and found that CT is an effective way of determining the severity of fracture. The more severe the fracture, the more likely a repair is necessary.
Imaging Pearls
- CT is the criterion standard for evaluating midface trauma.
- CT is not as suitable as MRI for assessing soft tissue changes and acute intracranial changes.
- Misinterpretation of facial suture lines can cause an inexperienced examiner to diagnose facial fractures when none is present.
- Previous hardware and dental fillings can cause a scatter effect, making interpretation of fracture difficult in certain circumstances.
- Previously, an adequate examination of the cribriform plate, orbital roof, and orbital floor required images in the coronal plane, necessitating a direct coronal CT scan. However, to acquire a direct coronal CT scan, the cervical spine had to be cleared, and this wasted valuable time. Obtaining a direct coronal CT scan also increased costs, increased patient exposure to ionizing radiation, and required transport of a potentially unstable patient to the scanner itself.
Magnetic Resonance Imaging
Accuracy
With regard to imaging the midface, the incidence of false-negative results are high with MRI, as compared with CT.
Imaging pearls
- MRIs are typically not helpful in cases involving acute bony trauma to the face. If there is a question of soft-tissue injury to nervous structures, MRI may be helpful.
- MRI is typically performed 48 hours after trauma. The signal intensity of blood on T1-weighted images varies, depending on the age and location of the blood.
- Generally, a radiologist has a low degree of confidence in MRI findings when assessing a facial fracture. MRI plays an adjunctive role in the examination.
- MRI does have a role in cases involving intracranial injury or in cases in which unusual soft-tissue injury may be present.
- MRI is superior in the evaluation of brain and dural-space injury.
Angiography
Imaging pearl
- Angiography may be needed if there is concern about an associated injury to the carotid artery or internal maxillary artery (eg, to identify the site of arterial bleeding before embolization).
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References
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Further Reading
Keywords
Le Fort fractures, floating palate fracture, Guerin fracture, floating maxilla fracture, pyramidal fracture, craniofacial dysjunction, floating face fracture, Wassmund fracture, Donat fracture, Manson fracture, Le Fort I fracture, Le Fort II fracture, Le Fort III fracture, LeFort I fracture, LeFort II fracture, LeFort III fracture
