Osteochondroma or osteocartilaginous exostosis is one of the most common benign bone tumours. It usually develops in the metaphyses of long flat bones, but rarely occurs in the oral and maxillofacial area, where it is generally associated with the coronoid process or the condyle. Loose osteochondromas inside the joint are generally a rare pathology usually described in large joints. The authors present a case of an intra-articular loose osteochondroma of the temporomandibular joint (TMJ), which represents the first case of such a pathological entity in the literature. The authors suggest that it should be considered in any differential diagnosis of loose bodies described in the TMJ.
Osteochondroma or osteocartilaginous exostosis, one of the most common benign bone tumours, consists of an exophytic bone proliferation with a hyaline cartilage cap protruding from the surface of the affected bone. It usually develops in the metaphyses of long flat bones, but rarely occurs in the oral and maxillofacial area, where it is generally associated with the coronoid process or the condyle. This tumour can occur singly or as part of an autosomal dominant syndrome known as osteochondromatosis. Different aetiologies have been proposed. The most recent theory is based on the presence of nests of chondrocytes in the periosteum. Mechanical stress may lead to hyperplasia of these cells, because the lesion is usually located in areas such as the tendon insertions. Malignant change is rare in solitary osteochondromas, approximately 2% of cases, but does occur in approximately 5% of cases of multiple hereditary osteochondromatosis. No case of malignant transformation has been reported in the skull. Most cases of condylar osteochondroma manifest with facial asymmetry or malocclusion (ipsilateral posterior open bite, contralateral cross bite) with limited temporomandibular joint (TMJ) movements. Loose osteochondromas inside the joint are a very rare pathology. Sarmiento and Elkins have reported a case that showed a large intra-articular osteocartilaginous loose body in the knee joint and termed it a giant intra-articular osteochondroma. Milgram and Dunn described a case that presented with an osteochondral tumour and two cases that presented with chondral tumours in the knee joint defined as an intra-articular osteochondroma and an intra-articular chondroma, respectively. Lim reported a case of extraskeletal osteochondroma of the buttock. There are no cases in the literature of TMJ involvement. The authors present a case of intra-articular loose osteochondroma of the TMJ, which represents the first case of such a pathological entity in the literature.
A 22-year-old woman presented at the authors’ department with facial asymmetry. She reported that it had appeared at the age of 15 years and had been gradually increasing. Her past medical history was unremarkable. She did not have any history of TMJ dysfunction and denied any recent trauma to the ear or mandible. Physical examination showed facial asymmetry with right lateral deviation of the chin ( Fig. 1 a) . The dental occlusion was characterized by class III malocclusion with a right lateral mandibular deviation ( Fig. 1 b–d). The patient had normal mouth opening, without deviation, and the mandibular range of motion was normal in all directions. There was no sound in the TMJ and no pain during the mandibular functionality examination. There was no facial nerve paralysis or paresis. The rest of the head and neck examination was unremarkable. A clinical differential diagnosis should include all the pathological conditions that can occur with mandibular deviation and malocclusion. The most common should include giant cell tumour, condylar hyperplasia, fibro-osseous lesion, vascular malformation, osteoma, chondroma, and osteochondroma. More rarely reported condylar tumours have included chondroblastoma, chondrosarcoma, osteoblastoma osteoid osteoma, enchondroma, osteosarcoma, and metastatic tumours.