Chapter 379. Temporomandibular Joint Disorders

Temporomandibular joint (TMJ) disorders in children are relatively rare. They can be divided into extra-articular and intra-articular types, which can occur alone or together.

The most common TMJ problem is myofascial pain, which is extra-articular in origin. The muscles of mastication can have a high resting tone, and they are often in spasm because of muscle hyperfunction or parafunction due to daytime and nocturnal jaw clenching (bruxism). Myofascial pain is more common in the morning and is often associated with a decrease in function. Related symptoms include headache, ear pain, joint noises, closed or open lock, difficulty chewing, and limited mouth opening.1

Intra-articular TMJ disorders that result from an abnormal relationship between the condyle and mandibular disk are also often associated with symptoms of myofascial pain.2 Spasm of the lateral pterygoid muscle, which inserts into the disk, can displace the disk anterior to the condyle.3 Anterior displacement with reduction occurs when the condyle moves under the displaced disk into a normal relationship and the opening movement occurs without impediment. This is usually associated with a midopening click, which can be audible and/or palpable. Anterior displacement without reduction is often the result of adverse loading of the TMJ or sudden trauma to the joint. When there is tearing and scarring of the retrodiscal tissues, the displacement is likely to be permanent and results in the disk losing its shape and becoming rounder, blocking the condyle from normal movement. When this occurs, the patient can only rotate, which limits opening to the 25-mm range.

Treatment

Treatment of myofascial pain is focused on diminishing muscle hyperactivity. The goals of therapy include eliminating behavior that is noxious to the muscles and joints; decreasing the frequency, duration, and intensity of pain episodes; providing support and counseling about stress reduction and other psychologic concerns; and establishing a functional and adequate jaw opening. Nonsurgical management is used to treat myofascial pain, and most patients respond well to this treatment.

Some of the nonsurgical treatment modalities include a soft diet with elimination of hard/chewy foods, thereby reducing the loading forces on the joint and decreasing muscle activity. Physical therapy to increase range of joint motion and muscle relaxation, massage of the muscles of mastication, and cold or hot compresses applied before and after exercises may also be helpful.4,5 Ultrasound can deliver heat to a depth of about 5 cm, and when done in combination with stretching, it can alter the elastic properties of connective tissue.6

Splint therapy with the use of a flat plane acrylic appliance that fits onto the dentition and disoccludes the teeth and jaws diminishes the loading forces on the discal tissue. Additionally, the splint distracts the condyle slightly out of the fossa and reduces pressure on the intracapsular tissues. Interrupting the normal proprioception of the masticatory system reduces muscle activity.7,8 Splints are frequently worn at night by patients with bruxism. However, patients with more chronic myofascial pain may need to wear the splint for up to 24 hours a day for a period of time to sustain symptomatic relief, and then the patient should be weaned from the splint.

Physiologic stress is thought to play an important role in myofascial pain.9 Pain and limitation of TMJ movement that results from stress-induced muscle contraction can be treated with a variety of stress-reduction techniques and biofeedback.10 It is important to communicate the role of stress to the patient and to obtain a history of recent stressors (school or work pressures, family troubles).11 Counseling may be indicated.

A variety of pharmacologic agents have been used to treat myofascial pain. Nonsteroidal anti-inflammatory agents are the most commonly administered. Anxiolytics reduce anxiety and muscle tension. Muscle relaxants invoke relaxation of skeletal muscle by a depressant effect on the central nervous system but with side effects. Analgesics are occasionally used for treating acute pain episodes. Antidepressants are useful in treating myofascial pain because a common psychiatric illness among chronic TMJ patients is depression.12 Because of the close relationship between chronic pain and depression, treatment for chronic pain, even without depression, sometimes yields responses to antidepressants.

More aggressive nonsurgical measures include trigger point injections of local anesthesia into areas of a muscle that are a palpable focus of hypersensitivity. Injection of botulinum toxin to paralyze a hyperactive muscle may also decrease pain.13 In more refractory cases in which the primary pathologic state is within the joint, arthrocentesis/arthroscopy of the upper joint space with lavage and lysis of adhesions and injection of steroids and/or sodium hyaluronate can be helpful.14,15

Inflammatory arthritis can affect the temporomandibular joints. Reports in the literature suggest that between 45% and 72% of children with juvenile rheumatoid arthritis have temporomandibular joint (TMJ) involvement.16,17 It is unusual for TMJ pain and inflammation to be the first presentation of undiagnosed juvenile rheumatoid arthritis, but within 5 years of diagnosis, 50% of children develop some TMJ symptoms.18 In the acute setting, there is usually swelling and tenderness of the joint with a variable amount of pain. There can be limitation of mandibular movement, which may progress to ankylosis (eFig. 379.1). Gross destruction of the condyle may reduce its vertical height, leading to anterior open bite and mandibular retrognathia19 (eFig. 379.2). The radiologic features are nonspecific and are observed in other destructive diseases. These include flattening, sclerosis, erosion, osteophyte formation, reduction of joint space, and reduced mobility. Treatment depends on the severity and stage of the condition but in general is similar to treatment of other joints: relieve pain, improve function, and prevent destruction and deformity. In the acute stage, medication is the treatment of choice. Orthodontic treatment in coordination with surgical intervention can correct the malocclusion and bony deformity that may develop but only after the inflammatory component of the disease has been controlled.

Idiopathic condylysis is an acquired TMJ disorder exhibited as a progressive decrease in condylar size and shape, unassociated with temporomandibular ankylosis or orofacial anomalies. To make the diagnosis, other causes of condylar resorption (eg, rheumatoid arthritis, systemic lupus erythematosus, trauma) must be ruled out. This condition is usually bilateral and has a predilection for females with an age range of 15 to 35 years.20 These patients often have preexisting TMJ dysfunction and a high mandibular plane angle.21-23 Patients exhibit a decrease in posterior face height, retrognathia, and an anterior open bite as a result of clockwise rotation of the mandible. Treatment involves an operation to restore the normal facial profile after documentation that the process has ceased.

Some of the other bony abnormalities of the temporomandibular joint seen in children include posttraumatic deformities, condylar hyperplasia, and tumors. Unilateral and bilateral intracapsular and subcondylar fractures are the most common mandibular fractures in children and can result in ankylosis, overgrowth, or undergrowth of the injured condyle with resultant facial asymmetry.24 Condylar hyperplasia is due to an abnormal hypermetabolic growth center in 1 condyle that leads to a malocclusion and progressive facial asymmetry.25 Treatment depends on the age of the patient, skeletal maturity, and the clinical and radiographic examination. High condylectomy (removing the abnormal growth center) and/or orthognathic surgery to reposition the jaw are the methods generally used to correct the resultant asymmetry and malocclusion.26 Tumors of the temporomandibular joint are rare, and the most common in this region include fibroosseous lesions (eFig. 379.3) and giant cell tumors. Resection of the tumor and reconstruction of the ramus condyle unit is usually indicated.