The TMJ is a paired synovial joint that is capable of both gliding and hinge movements. It articulates the mandibular condyle and the squamous portion of the temporal bone, with the articular disc of dense fibrous connective tissue interposed between the two bones. Unlike most other synovial joints, the TMJ is lined with dense fibrous connective tissue (Figure 26–2).
This disorder is an inflammation of the synovial lining of the TMJ; it is characterized by localized pain that is increased by the functioning and loading of the joint. Sometimes patients complain about posterior teeth not meeting on the same side, presumably because of swelling in the joint.
Patients often present with a history of pain in the preauricular region, which is aggravated by chewing or other mandibular movement. Pain on palpation over the lateral pole of the condyle is evident. Pain is elicited on loading of the TMJ, or on distraction or compression. Range of motion is often limited (<35 mm). No radiographic changes are found; however, evidence of joint effusion is seen on MRI. Treatment indications can be found in Table 26–1.
Table 26–1. Treatment Indications for Articular Disorders. ||Download (.pdf)
Table 26–1. Treatment Indications for Articular Disorders.
|Articular Disorder||Self-Care||NSAIDs||Physical Therapy||Splint||Acupuncture||Arthrocentesis||Surgery|
|Disc displacement with reduction||X||X||X||X||X||X|
|Acute disc without reduction||X||X||X||X||X||X|
|Chronic disc displacement without reduction||X||X||X||X||X||X|
Disc Displacement Disorders
Disc Displacement with Reduction
Disc displacement with reduction is characterized by a clicking jaw joint; an audible or palpable click is heard or felt on opening the mandible and in lateral movements of the mandible. This condition is most often painless and requires no treatment. Up to 50% of people have been shown to have displaced discs, and most do not have any pain or dysfunction. When pain accompanies the click, it is most often the result of inflammation in the joint owing to the condyle pressing on the retrodiscal tissues, synovitis, or capsulitis. Symptomatic clicking, in which there is pain on clicking and pain on loading, needs to be treated. MRI shows the anterior position of the disc in a closed position and in a normal position on opening. X-rays may show a decreased joint space, but this is not diagnostic of a displaced disc.
Acute disc displacement without reduction (closed lock) is characterized by a marked limitation in opening (<35 mm). It is also distinguished by a deflection of the mandible to the affected side on opening. It occurs with a sudden onset and can be painless or painful. No clicking is felt or heard, although the patient usually has a history of clicking at one time. The disc is usually anterior to the condyle and blocks the translation of the condyle, preventing normal opening and causing the mandible to deflect to the affected side. MRI shows the disc anterior to the condyle in the closed position, and it remains anterior on opening. Radiographs can show a decreased joint space that might be an indication of a displaced disc.
Chronic Disc Displacement
Chronic disc displacement without reduction (closed lock) is a long-standing condition characterized by a slightly limited opening (<40 mm) that usually improves after the initial onset. The patient has no clicking, either felt or heard, although he or she usually has a history of a previously clicking joint. Pain is not usually a complaint, and patients may or may not present with it. The mandible deflects to the affected side on opening. The disc is anterior to the condyle and is either pushed further anterior on opening or is folded on itself. MRI shows the disc far anterior, often folded on itself, and pushed further forward on opening.
Osteoarthritis is a noninflammatory arthritic condition that is characterized by deterioration and abrasion of the articular tissues. It is accompanied by remodeling of the underlying subchondral bone. Joint pain is present with function, and crepitus is often heard over the affected joint. Joint stiffness, often worse on awakening or at the beginning of a meal, can be a problem, and the patient may have a limited range of motion. Radiographic evidence of degeneration of the condyles can be seen. Synovitis often is present and accounts for pain, when present. The long-term prognosis is good because osteoarthritis tends to be self-limiting as the joint remodels.
Systemic polyarthritic disorders can affect the TMJ as well as other joints in the body. Various systemic diseases such as rheumatoid arthritis, juvenile rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, infectious arthritis, Reiter syndrome, gout, and Lyme disease can involve the TMJ. A common finding is pain to palpation over the TMJ. Pain is usually elicited with function, and the patient may experience a limited range of motion. Crepitus can be heard over the affected joint, and degeneration of the condyles may be seen on X-rays.
Condylar dislocation is characterized by a patient who is unable to close his or her mouth. The patient's mouth is fully open upon presentation, and he or she is usually in great distress, with pain and anxiety. This condition occurs after yawning, after eating an apple or other food that requires wide opening, or with prolonged opening, as during a dental appointment. The condyle remains positioned anterior to eminence. There can be joint pain at the time of dislocation and for up to several days afterward. There is usually a history of a self-reducing dislocation.
The condyle can be reduced by manually pushing the mandible both downward and backward into the fossa. This reduction can often be done in the office by placing gloved hands, with the thumbs outside the patient's teeth, on the lateral border of the mandible and distracting the mandible in a downward direction, placing the condyles back into the fossa. If the muscles have gone into spasm, it may be necessary to administer a muscle relaxant such as diazepam; in more severe cases, the patient may need to be placed under general anesthesia before enough muscle relaxation can take place to reduce the condyles. Postoperative pain is managed with NSAIDs, and physical therapy is indicated. Self-care can assist in preventing recurrences.
Fibrous ankylosis is restricted mandibular movement with deviation to the affected side on opening. This condition results from fibrous adhesions that attach the condyle to the disc and the disc to the articular fossa. It may be caused by bleeding in the joint, but the exact mechanism is not known. A history of trauma to the TMJ usually exists. There is a marked limited opening, usually <20 mm, but the condition is not painful. The mandible deflects to the affected side on opening, and there is a marked limited lateral movement of the mandible to the contralateral side. Radiographs show an absence of condylar translation, but they do show a joint space.
Bony ankylosis is the union of the bones of the mandibular condyle and the temporal fossa by proliferation of bone cells, which results in the complete immobility of the joint. It is usually secondary to trauma and probably due to bleeding in the joint. A history of trauma to the TMJ usually exists. There is a marked limited opening, usually <10 mm, although the condition is generally not painful. The mandible deflects to the affected side on opening, and there is a marked limited lateral movement of the mandible to the contralateral side. CT scanning or MRI shows a connection between bony articulating surfaces; X-rays show an absence of condylar translation and bone proliferation in the joint space.
Fractures can occur in any of the bony components of the TMJ; however, fracture of the mandibular condyle is the most common. It is often caused by a direct trauma to the jaw, usually by a blow to the chin. This condition is marked by a limited opening (<25 mm), swelling over the affected joint, and pain with function. There is often bleeding in the joint, and sequelae can include adhesions, ankylosis, and joint degeneration. The mandible deflects to the affected side, and the fracture is evident on an X-ray.
Condylar fractures are managed with immobilization, a soft diet, and physical therapy to regain the range of motion. Open joint surgery is required to reduce the fracture only in rare cases.