Temporomandibular joint

A fibrocartilagenous disc is present between the mandibular condyle and glenoid fossa. The temporomandibular joint disc is described in the sagittal plane as a bow tie-shaped structure, showing an anterior band, intermediate zone, and posterior band. In the closed mouth position, the posterior margin of the posterior band is situated above the condyle, not more than 10 from the 12 o'clock position relative to the condyle. When the mouth is opened, the condyle moves to the intermediate zone of the disc, and while the condyle shifts to a position below the articular eminence, this relationship is maintained (Fig.1). Also, see temporomandibular joint.

2. Pathology

Internal derangement

Pain and discomfort caused by internal derangement of the temporomandibular joint are frequent. An abnormal position of the disc relative to the mandibular condyle and the articular surface of the temporal bone is the most important cause of internal derangement of this joint. Often, the disc is dislocated anteriorly, with or without reduction when the mouth is opened. For a more detailed discussion, see internal derangement temporomandibular joint.

Arthritis

Chronic arthritis of the temporomandibular joints is seen primarily in rheumatoid arthritis temporomandibular joint (also, see rheumatoid arthritis), ankylosing spondylitis and in psoriatic arthritis.

Synovial chondromatosis

Also, see synovial chondromatosis)

Ganglion cyst

Fibrocystic structure that develops as a result of herniation of the synovium into the surrounding tissues, ectopic placement of synovial tissue, or post-traumatic degeneration of connective tissue. Such a cyst may clinically mimic a parotid tumour or periparotid adenopathy (Fig.2).

Tumours

Primary neoplasms include chondrosarcoma head and neck (also, see chondrosarcoma), fibrosarcoma and synovial sarcoma. The temporomandibular joint may be affected secondarily by neoplasms arising in the parotid gland, external auditory canal and by other local tumours.

Trauma

Temporal bone fractures may extend into the glenoid fossa. Condylar and subcondylar fractures mostly result from indirect trauma, commonly occurring in association with other fractures of the mandible. Also, see facial fractures, empty glenoid fossa sign.

RH