Abstract
Maxillofacial injuries can be complex and are clinically important due to their functional and cosmetic significance. Maltreated and missed fractures might cause deformity of the face; thus, accurate evaluation of the fracture provided by X-ray images is critical. In this study, we explore the application of cone-beam computed tomography (CBCT) for diagnosis of severe maxillofacial traumas. A patient with a complex fracture that affects the maxilla, mandible, wall of the maxillary sinus, zygoma, zygomatic arch and nasal bone was diagnosed using 3D reconstruction of CBCT images. This diagnostic approach provides detailed information obtained by static images and a systematic model with unique advantages for the following pre-surgical evaluation, surgical treatment and prognostic assessment of complex maxillofacial fractures.
Introduction
Maxillofacial fractures, a group of fractures of the skull bones, are a common complication of maxillofacial trauma. Among clinical cases of oral and maxillofacial trauma, the incidence of maxillofacial fracture is increasing. The etiologies of maxillofacial trauma may vary and can include traffic accidents, falls, accidents at home, sports-related injuries, domestic violence, interpersonal violence, work-related injuries, and assault [1–4]. Traffic accidents have become the main cause of maxillofacial injuries, accounting for more than 50% [4, 5]. Among the different types and locations of injuries, lower jaw fractures are the most frequent presentation, representing 46.5% of all maxillofacial fractures, followed by zygomatic bone trauma (34.9%) and nasal bone trauma (21.7%) [5]. The clinical manifestations of maxillofacial fracture include facial edema, ecchymosis, epistaxis, asphyxia, orbital margin deformity, trismus, hemorrhage, pain, abnormal nerve sensitivity and facial asymmetry [6].
Previously, conventional radiography along with clinical examination has played a major role in the diagnosis of maxillofacial fractures. However, the overlapping nature of bones and the inability to visualize soft tissue swelling and fracture displacement, especially in the face, make radiography less reliable and useful. Precise evaluation of the location, displacement, and extent of the bone fracture is essential for diagnosing and treating facial fractures, which requires both clinical and X-ray imaging examinations [7, 8]. Imaging techniques include traditional radiography, such as panoramic and lateral cephalograms, posterior bitewing radiographs and anterior periapical radiographs; traditional CT technology; and cone-beam computed tomography (CBCT).
Developed in the late 1990s, CBCT was first applied to dentomaxillo-facial images in 1998 [9]. This technique is suitable for imaging teeth and hard tissues in the maxillofacial region. The 3D tomographic data from CBCT are obtained during a single rotation of the X-ray tube and scanner between the sensor and the patient; the X-ray beam is cone-shaped (hence, the name of the technique), which differs considerably from medical CT [10, 11]. CBCT has multiple advantages, including a low radiation dose, low cost, rapid scanning time, low number of artifacts, real-time image analysis and higher resolution and accuracy in all 3D images of the alveolar bone compared to CT [12, 13]. With the rapid development of radiologic technology, CBCT has been commonly used in the clinical practice of dentistry and medicine for purposes such as analyzing root position and structure [14, 15], diagnosing lesions in the airway and surrounding structures [16, 17], temporomandibular joint evaluation [18], determining the positions of impacted teeth [19, 20], orthognathic surgical planning [21], evaluating skeletal asymmetries [22, 23],and identifying the position of the inferior alveolar nerve [24]. In addition, CBCT imaging procedures may also include ear, nose and throat images, suggesting that the applications of CBCT are expanding to certain otolaryngology-related procedures [25]. CBCT radiography administers a low exposure dose to the patient that corresponds to 3% to 20% of the dose of a traditional CT and is comparable to the dose of a 2D X-ray film but produces higher resolution images [26]. CBCT can also generate 3D static images and rotatable reconstructed images. In addition, 3D static images can provide 3D information about a specific site, while 3D rotatable images can be rotated in each direction [27–32], and changes in the teeth and alveolar bone during and after treatment can be clearly observed. A comparison of the advantages and disadvantages of common radiological modalities used to evaluate maxillofacial fractures is presented in Table 1.
Comparison of the advantages and disadvantages of plain films, traditional CT technology and CBCT
Comparison of the advantages and disadvantages of plain films, traditional CT technology and CBCT
Abbreviations: CBCT:cone-beam computed tomography.
In this paper, we report a case of an adult maxillofacial trauma patient with complex fractures diagnosed by CBCT. The effect of 3D rotatable images and static images generated by CBCT on the diagnosis and treatment of complex fractures in the maxillofacial region is discussed, and the related references are reviewed.
A 44-year-old male was referred to our clinic complaining of double vision in all viewing directions but without deficits in global mobility and no loss of vision for approximately 10 days. He initially presented to the local physician with multiple injuries in the maxillofacial region and abdomen due to a fall from a height of 10 meters one month previously. The patient had initially undergo emergency surgery, with open reduction and internal fixation (ORIF) of the maxillary and mandibular fractures. Surgery was performed through an incision to expose the fracture site, and titanium was used to repair the fractures. Postoperatively, the patient complained of double vision.
On physical examination, the patient’s face was asymmetric. The right zygomatic arch was more prominent than the left, with step deformity and tenderness on palpation. The right infraorbital rims were collapsed without step deformity on palpation. The lateral margin of the right orbit was irregular on palpation with step deformity and tenderness. An approximately 3 cm incision was present on the left side of the lower eyelid. The left nasal bone was higher than the right nasal bone. The bilateral globe was not in a horizontal plane; double vision was noted bilaterally, but the patient had no deficits in global mobility or loss of vision. The oral opening was less than 20 mm. The patient had poor oral health, and thick dental calculus bands were observed. Premature contact was observed between the maxillary right second molar and the mandibular right second molar. The maxillary left first molar and the mandibular left second molar also exhibited premature contact. Open bites were observed in the remaining teeth. The maxillary right first premolar, left central incisor and left second molar were missing.
CBCT examinations were performed using a device with a 20×25 cm flat-panel detector (aSi) (KaVo 3D exam; KaVo, Biberach, Germany), and the data were reconstructed using i-CAT Vision software (Imaging Sciences International, Hatfield, PA). Pre- and post-treatment 3D rotatable images were generated using Dolphin Software (version 11.0; Dolphin Imaging Systems, Chatsworth, CA). On CBCT, five titanium plates were visualized that had been used to fix the mandibular and maxillary fractured bones; however, the bone fractures had not been fixed, including those in the right zygoma, the right side of the zygomatic arch, the wall of the maxillary sinus and the right side of the nasal bone (Fig. 1).
Pre-treatment CBCT static images. A: The patient’s face was asymmetric, and the right zygoma and infraorbital margin were collapsed, B-E: Five titanium plates had been used to treat the mandibular and maxillary fractured bones; however, the fractures of the right zygoma, the right side of the zygomatic arch, the wall of the maxillary sinus and the right side of the nasal bone had not been fixed.
The objectives of the second surgical treatment were to (1) re-establish the patient’s original occlusal relationship and improve his masticatory function, (2) correct the double vision and (3) improve the facial asymmetry. To achieve these goals, an open reduction and internal fixation technique was performed to manage the multiple facial bone fractures under general anesthesia.
The 3D reconstruction imaging data were input to a 3D printer to yield a rapid prototyping model of the same size as the patient’s maxillofacial region before the operation. Simulations of the fracture surgery and pre-forming of the titanium plate were conducted on the model. During surgery, the fracture condition corresponded to the preoperative evolution. The 3D reconstructed CBCT images accurately replicated the multiple facial fractures. The surgical duration was 290 minutes, which is a significantly shortened operation time. The patient postoperatively underwent inter-maxillary elastic traction to ensure the healing of fractures with a stable occlusal relationship.
On clinical re-examination one month after surgery, the patient’s diplopia symptoms and malocclusion were relieved, and good recovery of his facial appearance and masticatory function were observed. On static CBCT images, the fracture lines of the right side of the zygomatic arch, lateral orbital margin and infraorbital margin were fixed with three titanium plates, and the broken ends were well aligned. The anterior nasal spine fracture was fixed with one titanium plate (Fig. 2). The fracture line was blurred, and bony calluses extended through the fracture line. On the overall perspective of the 3D rotatable images, the facial appearance and occlusal relationship were notably improved. The heights of the bilateral zygomata reached nearly the same levels. In addition, the fractures of the right side of the zygomatic arch, lateral orbital margin and infraorbital margin and the nasal bone reduction had healed well. The fracture line was blurred, and bony calluses were observed through the fracture line (Fig. 3).
Post-treatment CBCT static images. A: The heights of the bilateral zygomata were symmetric, and the right side of the infraorbital margin was not collapsed. B: The titanium plates used to fix the mandibular fractures were removed, and the broken ends were well aligned. C-E: The fracture lines of the right side of the zygomatic arch, the lateral orbital margin and the infraorbital margin were fixed with three titanium plates, and the broken ends were well aligned.
The facial bones are the most prominent areas and are also the most complex anatomical structures of the human body. In addition, they are the most vulnerable to injury. Facial injuries can cause significant aesthetic and functional problems, affecting the facial appearance, sight, smell, hearing, speech, breathing, and eating, which can subsequently lead to psychological distress in the patient after trauma [33, 34].
Patients with facial trauma must be treated as quickly as possible. In all types of facial bone fractures, the primary focus of treatment is to recover the occlusal relationship using either manual reduction or surgical reduction depending on the degree of trauma severity. An accurate and prompt diagnosis using X-ray images is critical for the treatment of facial trauma. In this study, we used 3D rotatable CBCT technology to generate 3D images and printed a simulated model for the surgery. Based on 3D image information, we used open reduction and internal fixation surgery to treat multiple broken maxillofacial bones and reconstruct the facial tissue. The patient’s double vision and malocclusion were relieved after surgery. Furthermore, after treatment, CBCT showed marked improvement of the facial appearance and occlusal relationship; the fractures of the maxilla, mandible, and zygoma and the nasal bone reduction had healed well. The fracture line was blurred, and bony calluses extended through the fracture line.
A correct pre-surgical diagnosis is based on the clinician’s experience, a thorough clinical examination, and clear imaging information. Traditional or digitally captured plain radiographs are limited by the fact that the complex 3D anatomy of the maxillofacial region is depicted in a 2D image, and structures can be superimposed, magnified, distorted, and misrepresented [8]. Traditional CT technology also provides 3D images; however, compared to CBCT, the disadvantages of CT include the high radiation doses and cost of the examination, long scanning times, a certain degree of deformation and the generation of image artifacts by metal-containing dental materials (e.g., metal ceramic crowns or tooth filling materials) [35–37]. The application of CBCT in complex maxillofacial fracture diagnosis and treatment is of great importance. Plain film 2D radiographs, such as panoramic radiographs, may be conducive to initial examinations of maxillofacial trauma; however, minimal displacement or oblique fractures may not be clearly represented, and occult fractures may require CBCT techniques, which can provide excellent resolution images of bony structures and the surrounding tissues [38]. Panoramic radiographs can reveal pathological changes in mandibular body fractures but cannot clearly show the direction and degree of condylar fracture displacement, especially in high condylar fractures [13, 39].
Software such as Dophin, Invivo, and Anatomage can be applied to create 3D reconstructed rotatable images before and after treatment by utilizing the original CBCT data. 3D rotatable images have certain advantages that other radiological technologies do not have. First, 3D images can be rotated, and the information can be observed from different angles and directions, such as the coronal, axial and sagittal planes; consequently, numerous 2D X-ray images can be replaced by the 3D-rotatable image. In addition, 3D reconstruction software with multi-angle display functions reveals information regarding fracture displacement and comminution as well as the degree of displacement. This allows convenient and efficient communication between clinicians and the patient or their family members and results in a better understanding of the patient’s pathogenic condition, which provides a good foundation for cooperation between doctors and patients. Third, the data from 3D reconstruction images can be used to create a 3D printed model, and we can simulate the fracture surgery and the pre-forming of fracture fixation materials on the model before surgery, which accurately predicts the surgical protocol and the final prognosis. Finally, by comparing the pre- and post-treatment 3D rotatable images, the treatment outcome can be clearly and directly assessed. In this case, the site and direction of the fracture lines, the displacement of the fragment, and the occlusal relationship could be observed from different directions. With the help of this information gained from the 3D static images and the rotatable reconstructed images generated by CBCT scanning, clinicians can engage in better diagnosis and therapeutic planning, which may significantly affect the patient’s final treatment.
While CBCT has its unique advantages in dental applications, it also has several limitations. For instance, CBCT can provide 3D information about bony structures but has a low contrast resolution and a limited capability of visualizing the internal structure of soft tissues and soft-tissue lesions. In conclusion, CBCT is an appropriate radiographic technique to obtain static images and 3D rotatable reconstructed images for the diagnosis of maxillofacial fractures.
