Osteochondroma is a benign tumor of bone and cartilage. It is common in axial skeleton bones such as femur or tibia, but rare in the maxillofacial region [4]. In the mandibular condyle, osteochondroma may co-occur with chondroma and osteoma [3]. It occurs slightly more often in females than in males (1.22:1) [5]. Clinical manifestations of osteochondroma of the mandibular condyle are facial asymmetry, malocclusion, and joint pain [6]. Seki et al. reported a case of an osteochondroma patient with complete hearing loss [7]. Initially osteochondroma usually presents no symptoms, but symptoms may develop as the tumor size increases. The tumor may impinge on adjacent anatomic structures, such as nerves and bones [8]. Usually, slowly growing osteochondroma causes gradual vertical elongation of the affected side [6], but sometimes patients cannot recognize pathologic changes of their jaws. Our patient had facial asymmetry with chin deviation to the right side, severe malocclusion with crossbite and left TMJ pain.
A genetic component may be involved in this disease [9]. Another factor that increases the risk of osteochondroma is trauma [10]. However, the etiology of this disease is not clear. Our patient stated that she had no history of trauma to the left TMJ area and no systemic diseases.
Some patients exhibit vertical elongation of the affected side and slight pain [5]. Panoramic view and computed tomography (CT) can be valuable tools to diagnose this tumor. In panoramic view, osteochondroma can be detectable as an exophytic mass with mixed density and sclerosed appearance [1]. CT is more useful than panoramic view to visualize the mass and the relationships among adjacent anatomic structures [6].
Facial asymmetry and malocclusion may also be observed in condylar hyperplasia and other differential diagnoses such as osteoma, chondroma, fibrous dysplasia, fibrosarcoma, and chondrosarcoma [11]. Thus, histopathological diagnosis is important. Histopathologically, osteochondroma represents bone proliferation with a hyaline cartilage–capped osseous growth [2,3]. In contrast to other bone tumors, chondrocytes of osteochondroma show intracytoplasmic eosinophilic inclusions or hyaline globules inside them [2].
On histological observation, the present osteochondroma showed diffuse proliferation of chondroid tissue, which partly produced ossifying trabecular bones. The chondroid tissue was conspicuously positive for BMP-4 and the trabecular bones were slightly positive for BMP-2. Most chondrocytes were surrounded by hyalinized chondroid material and showed rare PCNA immunoreaction. Therefore, we presume that the present tumor was derived from condyle chondrocytes that showed ossification, and are confident in the osteochondroma diagnosis. We also believe that the present osteochondroma was a relatively well-differentiated benign tumor with low proliferative potential.
The protocol for treatment of osteochondroma of the mandibular condyle is controversial. If only the head of the condyle is involved without tumor extension into the neck, local resection or conservative condylectomy with contouring the affected condylar head can be the appropriate choice [1]. However, conservative approach may result in recurrence of the lesion or malignant changes [5]. In case of osteochondroma requiring the removal of the condylar head and neck, total condylectomy with joint reconstruction is recommended [12]. Costochondral or sternoclavicular grafts are considered for the reconstruction of the condyle, but in this case donor site morbidity and bone resorption are possible [13]. Alloplastic TMJ replacement may be performed, but it may lead to infection and heterotopic bone formation [14]. We performed high condylectomy to remove the mass. For 12 months after surgery, the patient had not complained of any discomfort and we could not find any signs of recurrence or malignant changes.
Deviation of the mandible because of osteochondroma of the mandibular condyle can also change the occlusion plane. In this case, orthognathic surgery should be considered. It can re-establish optimal occlusion and improve facial aesthetics [3]. There are many benefits of simultaneous TMJ and orthognathic surgery. First, only one operation under general anesthesia is required. Second, the surgeon can balance the occlusion, TMJs, jaws, and neuromuscular structure at the same time. It also reduces the overall treatment time [15]. In our case, the patient showed canting of the occlusion plane right and up by 3 mm. Because the chief complaints of the patient were facial asymmetry and malocclusion, we used both Le Fort I osteotomy and mandibular set-back surgery with removal of osteochondroma via condylectomy. It was possible that a small portion of the osteochondroma lesion still remained in the mandibular condyle. However, the patient’s mandibular condyle healed uneventfully and functioned well with no evidence of recurrence. Therefore, condylectomy performed in this study seemed to be appropriate. Although we are planning to perform additional follow-up checks, we presume that condylectomy with bimaxillary orthognathic surgery was effective in this patient. At 12 months post-operation, the patient was satisfied with the outcome.
