Although nasal fractures are the most common facial fracture, they often go unnoticed by physicians and patients. Patients with nasal fractures usually present with some combination of deformity, tenderness, hemorrhage, edema, ecchymosis, instability, and crepitation; however, these features may not be present or may be transient. [1, 2, 3] To further complicate the matter, edema can mask underlying nasal deformity, crepitation, and instability; thus, many physicians and patients fail to pursue further diagnosis and appropriate treatment.  Radiologic features of nasal fractures are demonstrated below.
If untreated, nasal fractures can result in unfavorable appearance and function, especially when the underlying structural integrity of bone and cartilage is lost. [2, 5] Untreated nasal fractures account for the high percentage of rhinoplasty and septoplasty procedures performed months to years after the initial trauma occurs. Thus, appropriate treatment is best rendered in a timely manner, before scarring and soft tissue changes occur. As always, thorough history taking and physical examination should precede radiographic evaluation.
If radiographic evaluation is warranted, it is best used when other facial fractures are suspected in combination with a nasal fracture, because isolated nasal fractures are treated on the basis of the physical examination alone. The fact that patients may have displaced nasal fractures and normal-appearing plain radiographic findings should be emphasized. [1, 3, 6, 7, 8, 9, 10, 11, 12, 13]
Nasal bone fractures account for 50% of all facial fractures, with the majority of these injuries involving the cartilaginous lower two thirds of the nose.
Lateral impact injuries are the most common type of nasal injury leading to fracture.  Nasal fracture and displacement without septal fracture usually occur with weaker applied forces; however, with increased force, displacement of the bilateral nasal bones may be noted, and the septum is usually dislocated and fractured as well. 
Approximately 80% of fractures occur at the lower one third to one half of the nasal bones. This area represents a transition zone between the thicker proximal and thinner distal segments.
Other injuries that are commonly associated with nasal fractures include midface injuries involving the frontal, ethmoid, and lacrimal bones; nasoorbital ethmoid fractures; orbital wall fractures; cribriform plate fractures; frontal sinus fractures; and maxillary Le Fort I, II, and III fractures. [1, 3, 9, 10, 13, 14]
Nasal fractures account for approximately 40% of all bone injuries. Fights and sports injuries are the most common causes of nasal fractures in adults, followed by falls and vehicle crashes. Play and sports account for the majority of nasal fractures in children. Physical abuse should be considered when evaluating children and women with nasal fractures. Nasal fractures may occur in isolation, but are commonly associated with other facial injuries and fractures.
The nose is the most prominent and anterior facial feature; as such, it is also the most readily exposed to trauma. The nose is supported by cartilage on the dorsum and caudal aspects and by bone posteriorly and superiorly. The paired nasal bones, the maxillary crest, and the nasal bones, jutting from the frontal bone, form the bony framework that supports the underlying nasal cartilages. The entire lower two thirds of the nose is cartilaginous.
Overlying the framework of the nose are soft tissues, including muscles, nerves, and mucous glands. The lower two thirds of the nose houses 2 upper lateral cartilages, which originate from underneath the inferior aspect of the nasal bones and project into the scroll region of the nose just superior to the nasal tip. The paired upper lateral cartilages are continuous with the dorsal nasal septum. The septum has a dorsal, caudal, posterior, and maxillary attachment as its components and is often referred to as the quadrangular cartilage. The lower lateral crura are composed of the medial, intermediate, and lateral crural components. The medial crura attach to the septum with adhesive ligaments at the caudal septum, giving structural support to the nasal tip, which is composed of the transition between the intermediate and lateral crura.
Although the use of plain images is not suggested, the preferred examination includes the acquisition of Waters (occipitomental) and lateral nasal views if plain films are used. It should be noted that plain radiographs only serve to confuse the clinical picture in most cases. Plain radiographs do not allow identification of cartilaginous disruptions, fractures, shearing, and injury in general. Plain radiographs also do not provide sufficient information to assess injury severity and displacement, 2 important aspects essential to emergent and delayed management and surgical planning.
A good physical examination of the internal and external nose is still the method of choice for detecting and assessing nasal fractures.
For questionable fractures and fractures that may be associated with other facial trauma, a CT scan of the facial bones without contrast is an excellent choice. Modern multidetector CT scanners have revolutionized trauma imaging and provide a fast, safe, cost-effective, and sensitive means for assessing trauma of the bone and soft tissues. Three-dimensional reconstructions are easily derived from these scanners and readily show the degree of displacement if substantial trauma exists. [15, 16]
Limitations of techniques
The use of plain images and computed tomography (CT) scans for the diagnosis and management of nasal fractures has been controversial. Several small studies have shown that use of these modalities is neither cost-effective nor beneficial to the patient or physician. Nasal fractures are usually evident and can be elicited by means of careful history taking and physical examination. Rarely is the radiologic confirmation of these injuries needed.  However, some clinicians still use plain images and CT scans, and the radiologist must understand some of the diagnostic pitfalls to reduce the rate of erroneous readings. [18, 19]
Wexler opined that nasal radiographs were a medicolegal necessity and considered them an important adjunct in acute injuries to the nasal bones.  Unfortunately, this opinion was not founded on solid experimental data. The practice of ordering unnecessary radiographs encourages poor patient care and devalues the importance of thorough history taking and physical examination. This practice also leads to needless irradiation, expense, and wasted time. [21, 22, 23, 24, 25]
Lee et al compared high-resolution ultrasonography (HRUS) with CT in diagnosing nasal fractures in 140 patients with nasal trauma from 2004-2007. The accuracy rates for HRUS, CT, and conventional radiography were 100%, 92.1%, and 78.6%, respectively. Compared with HRUS, CT revealed only 196 of 233 lateral nasal bone fractures. In high-grade fractures, the accuracy of CT was 87%, but it decreased to 68% in low-grade fractures. 
De Lacey et al concluded in a study that a lateral plain radiographic view was unreliable for the evaluation of nasal fractures because of the high incidence of similar defects found in noses from control subjects and in patients with dry skulls, when evaluated using plain radiography. In their study, the investigators evaluated 100 consecutive patients presenting to the emergency department with a history of trauma to the nose. 
Nasal radiographs were obtained in each patient, including the Waters and lateral views. There were no radiographic findings of fracture in 65 of the 100 patients. Nasal fractures were depicted in 45 patients, yet only 3 patients required reduction, and 31 of 45 patients were discharged without treatment. The authors then compared the lateral radiographs in 50 control subjects and 50 persons with dry skulls.
When images from control subjects were compared with images of persons with dry skulls, misreads were identified and classified as midline defects, high lateral-wall defects, and low lateral-wall defects. In 50 control subjects, 33 cortical defects were observed. After close inspection, the misreads were found to be the result of the midline nasal suture, the nasomaxillary suture (low defect), and thinning of the nasal wall (high defect). 
Clayton and Lesser concluded that examination under anesthesia provided more accurate information about nasal injury than did radiography or clinical examination alone or together. The authors prospectively evaluated 54 patients clinically, radiologically, and under anesthesia within 19 days after nasal injury.  Waters views and lateral views were obtained in all patients. External examination and nasal rhinoscopy were performed to evaluate the patients clinically.
The authors not only concluded that examination under anesthesia provided more accurate information than did the other examination methods, they also found that the Waters view, the lateral view, or the 2 views in combination were less useful than was physical examination alone. Standard radiographs were not helpful in deciding whether to perform manipulation for repair or when and how such manipulation should be performed.
When evaluation of children is necessary and one wishes to limit exposure to radiation, ultrasonography has been helpful to some in evaluating nasal fractures, septal deviation, and level of comminution. This can be accomplished with a 7-15 MHz linear array transducer. 
In the utilization of 3-dimensional (3D) CT scanning for facial and nasal fractures, better evaluation scores were achieved with surface rendering protocols than with volume rendering protocols. Surface rendering offered better overall image quality than did volume rendering. 
The legal value of an examination depends on the degree of medical findings supported by the examination results.  In isolated cases of nasal trauma, radiographs have a high number of false-negative results and a large, but unknown, number of false-positive results. Thus, the legal value is low because of the uncertain degree of confidence in the findings. Radiographic examinations of the nose have been known to fail in the assessment of nasal fractures. 
Features of the Waters and lateral radiographic views of nasal fractures are discussed in this section.
The Waters (occipitomental) view is perhaps the best overall view for observing facial fractures in general. The radiograph is obtained in the posteroanterior position, with the canthomeatal line at an angle of approximately 37° relative to the surface of the film (see the image below). The patient's dentures and oral prosthetic devices, if any, should be removed, because these structures may cause interference.
The Waters view demonstrates the orbits, maxillae, zygomatic arches, dorsal pyramid, lateral nasal walls, and septum (see the images below). The radiologist should look for abnormalities of the nasal septum and arch, keeping in mind the areas of relative weakness. Marked deviation, displacement with sharp angulation, and soft-tissue swelling are signs of possible fracture. Soft-tissue edema can be sufficient to obscure the extent of a fracture.
Other structures, such as the frontal, maxillary, and ethmoid sinuses, may also be involved. Any such involvement should alert the physician to the possibility of concomitant fractures. Some have found that coronal sutures can mimic nasal fractures, because the sutures can become superimposed over the nasal bones. 
The lateral view (profilogram) is obtained with the infraorbitomeatal line parallel to the transverse axis of the film and the intrapupillary line perpendicular to the plate. This orientation provides a true lateral projection that is neither tilted nor rotated; therefore, paired structures are superimposed. Many prefer to include the full profile from the forehead to the chin with a technique that uses a Bucky grid (see the images below). 
Fractures of the nasal bones are frequently transverse. The lateral view obtained by using a soft-tissue technique is probably best for depicting old and new fractures of the nasal bones. The profilogram provides no information regarding a possible laterally displaced nasal bone. [7, 29] Short, lucent lines that reach the anterior cortex of the nasal bone, with or without displacement, should be regarded as a fracture.  Evaluation of air zones by profilogram can provide important information, because the air zones commonly are lost after trauma. Alterations of air-zone shapes may indicate cartilage volume increases or septal hematoma. 
Other lines, such as normal sutures or longitudinally oriented nasociliary grooves, can be mistaken for longitudinal fractures. However, a nasociliary groove should never cross the plane of the nasal bridge; if this is demonstrated, the line is a fracture. Fortunately, fractures usually demonstrate a sharpened delineation, with greater lucency than normal sutures and grooves.  The radiologist must look closely for marked deviation, displacement with sharp angulation, and soft-tissue swelling.
It is important to remember that only approximately 15% of old fractures heal by ossification; as a result, old fractures are easily mistaken for new fractures, and this increases the rate of false-positive readings. 
Degree of confidence
Radiographic findings consistent with nasal fracture may be identified in 53-90% of patients with isolated nasal fractures.  Because of this and other concerns, Logan et al questioned the reliability of nasal bone radiographs. 
Similarly, a study by Hwang et al also suggested that plain radiography is unreliable in the diagnosis of nasal bone fractures and that CT should instead be used in such diagnoses. The investigators examined the use of plain radiography in the evaluation of 503 nasal bone fractures, using the lateral and Waters views.  Only 82% of nasal fractures were identified with plain films.
Logan et al believed that the high percentage of false-negative and false-positive results with nasal bone radiographs had a number of causes. Old fractures, vascular markings, cartilage fractures, midline nasal sutures, nasomaxillary sutures, and thinning of the nasal wall represent a few of the many features that may mislead even an experienced radiologist. The authors reported a true-positive rate of 86% and a false-positive rate of 8%. 
De Lacey et al conducted a similar study, which showed that 66% of control subjects had a false-positive reading using Waters view radiographs.  Unfortunately, an accurate depiction of the rate of false-positive and false-negative results from injured patients cannot be obtained by using their data.
CT scans are usually obtained when another traumatic facial or skull fracture is suspected. Many fractures are also demonstrated on routine head CT scans in patients with trauma. Although CT scans can be used to demonstrate the extent of nasal injury, they are rarely required. Contiguous, thin (2-3 mm), axial and coronal sections with bone windows must be obtained; however, axial images can be used to reconstruct coronal planes. These scans are helpful when associated injuries are suspected in combination with nasal fractures. [15, 16]
The CT-scan characteristics of nasal fractures are demonstrated in the images below.
CT scans depict important structures, such as the orbital walls, zygomatic arches, frontozygomatic sutures, maxillary buttresses, ethmoid air cells, nasal bones, dorsal pyramid, and floor of the frontal sinuses with the associated nasofrontal ducts. Recent nasal fractures usually are easily recognized on CT scans; however, as with plain radiographs, old fractures and normal sutures may be mistaken for new fractures.