Fibrous dysplasia (FD) is a slowly progressing bone lesion resulting from the displacement of normal medullary bone with abnormal fibro-osseous connective tissue. FD can be classified as monostotic when it involves a single bone and polyostotic when it involves multiple bones [1]. The former has an incidence of 70–80%, while the latter may be seen in 20–30% of patients with FD [13,14,15]. The monostotic form is usually asymptomatic, whereas the polyostotic form, accompanied by various endocrine disorders, irregular skin pigmentation, and early sexual maturity, is called McCune–Albright syndrome [1, 3, 16]. The monostotic type is more prevalent in the maxilla in the craniomaxillofacial skeleton [1, 3, 17]. In a patient whose only clinical feature is monostotic fibrous dysplasia, biopsy and identification of a somatic gene mutation may be required to confirm the diagnosis [1]. However, many experienced clinicians and radiologists will often notice that a lesion appears characteristic of FD on radiographic examination because it is an expansile and intramedullary lesion with a ground-glass appearance, thus diagnosing FD without the need for biopsy in typical cases [3]. Diagnosis can also be made by histologic examination of the biopsied tissue. The typical microscopic features of FD include a background of loosely arranged fibrous stroma with irregularly shaped bony trabeculae. The bone trabeculae are thin and disconnected to each other and have been described as “Chinese characters” [1, 3, 12, 18].
The differential diagnosis of the condition includes ossifying fibromas, cemento-ossifying fibroma, cemento-osseous dysplasias, aneurysmal bone cyst, cherubism, and giant-cell granuloma [1, 3, 19]. The lesions are grouped together because of their common histological features that include fibrous material mixed with bony structures and some elements of irregular woven bone [1, 12].
FD in the craniofacial area can cause significant expansion of the bones with facial asymmetry and disfigurement. In some cases, FD can cause displacement of structures, such as the orbit that can lead to visual disturbances and the auditory canals that can lead to hearing impairment [20]. The progression of the lesion into the oral cavity can compromise masticating and speaking. Periodontal and occlusal changes may also present, and this condition may require orthodontic treatment and orthognathic surgery to correct the malposition of the involved teeth and jaw [21].
Many clinical studies have reported that the appropriate treatment for this lesion depends on its location, its effect on function, and, ultimately, cosmetics. Oftentimes, the monostotic form is incidentally discovered on radiographs, and it is usually asymptomatic. Such lesions ordinarily pose no risk for pathologic fracture or deformity, and only clinical observation is warranted. Follow-up radiographs should be made every 6 months to verify that there has been no progression [13].
Surgical therapy is an effective management option for patients with cosmetic problems and deformities, and it is the preferred treatment to avoid pathological fractures and remove symptomatic lesions [9,10,11]. The available treatment options include radical resection, conservative contouring, and curettage. Conservative shaving or contouring has been recommended by some authors [18, 22] who maintain that periodic contouring could be performed until a static phase is reached. Total resection and reconstruction with a bone graft is considered to be the standard surgical procedure in cases of moderate to severe fibrous dysplasia [7, 8]. However, because of the neurovascular structures and external incision scar, surgical intervention is often challenging.
Until now, some surgical accesses have been proposed for the treatment of FD in the midface, such as the buccogingival or bicoronal approach, the Weber–Ferguson incision, and the midfacial degloving approach [22, 23]. The selected approach should provide adequate exposure of the lesion, minimal scarring, and minimal risk of injury to nerves or other vital structures. However, midfacial FD tends to be under-corrected due to the limits of the approaching methods, even using the bicoronal approach. The Weber–Ferguson incision causes a large range of facial scars because of the external incisions. The buccogingival incision has limitations on direct access to the orbital rim and temporal process of zygoma. However, the midfacial degloving approach fulfills most of the above requirements. The midface degloving approach first described by Casson et al. [24] is useful in corrective surgery for broad midfacial deformities, as in our case. Although this procedure requires precise surgical technique and a thorough understanding of the anatomy of the midface, the advantage of this technique is excellent bilateral exposure of the mid third of the face, including the maxilla, paranasal sinus, and nasal cavity, without skin incision [25]. With this wide surgical field, we could perform a delicate osteotomy, shaving the projected portion of the facial bones under direct vision.
Indications for this procedure include a wide variety of benign maxillary or sinonasal conditions, such as ameloblastoma, inverted papilloma, and various odontogenic or nonodontogenic cysts [25]. Particularly advantageous is the use of this procedure in the management of locally aggressive, histologically benign lesions such as odontogenic keratocyst and ameloblastoma where complete removal of the lesion is recommended without facial incisions. This approach can also be used in benign fibro-osseous conditions, facial fractures, orthognathic surgery, and bone grafting [25, 26].
The most common complications of the midfacial degloving technique are moderate transnasal crusting and facial paresthesia [27, 28]. Nasal crusting is unavoidable as an immediate postoperative sequela but subsides as regrowth of mucosa occurs. Infraorbital numbness and paresthesia should resolve in few months if the infraorbital nerves were carefully preserved during surgery. The rate of permanent infraorbital anesthesia has been reported to be less than 3% [29]. Nasal cosmetic deformities are rare complications and can be avoided with precise intranasal reapproximation. Problems such as postoperative nasal bleeding, vestibular stenosis, and oronasal or oroantral fistula are infrequently encountered. Vestibular stenosis and fistula formation can be avoided if the incisions are sutured promptly and meticulously [29, 30]. Other complications may arise secondary to midface osteotomies, such as epiphora during a medial maxillectomy.
In the present case, a FD lesion in the right maxilla and zygoma area was successfully removed by the midfacial degloving approach. This technique ensured complete visualization of the zygomatic prominence and the infraorbital rim, which was helpful in identifying and controlling the symmetry and width of the face. Furthermore, wider exposure of the facial skeleton helped us to better estimate the normal facial contour. Despite excessive undermining of the midfacial region, our patient showed good cosmetic results without sagging of tissue, deviation of the nose, or flattened ala. Mild swelling and paresthesia around the infraorbital nerve resolved spontaneously, and occlusion state was well maintained.
Although the use of the midfacial degloving approach was rare in the treatment of FD, some published papers have reported very similar cases [31,32,33]. In patients in their teens and twenties, facial asymmetry and swelling were found, and no other symptoms such as pain or visual disturbances, loosening of teeth, or paraesthesia over the face were observed. Except for one case, other cases were unilateral maxillary FD. The range of the expansile lesions included the maxillary bone involving maxillary alveolar process, hard palate, zygoma, and medial wall of orbit. Since the typical buccogingival incision was limited to access to the lesions, surgery was performed using the midfacial degloving approach. The surgical procedures and methods that contour the facial bone were similar to this case. There were no recurrence of the lesion and serious complications, and the esthetic result was satisfactory for the patients. However, in one case that has bimaxillary and mandibular FD, allocartilage and orbital surgery for correction of severely deviated nose and severe orbital dystopia were required [33].
