TMJ Disc Displacements

Introduction

Temporomandibular joint dislocation, also known as intervertebral disc dislocation, is an abnormal relationship between the articular disc, mandibular condyle and mandibular fossa [1]. Most common disc displacement occurs anterior to the mandibular condyle, but can occur in rare cases behind. The prognosis for these conditions is good and usually recovers with minimal intervention or conservative treatment. [1]

Limited TMJ opening[2]

Imaging studies have shown that a more anterior disc position is relatively common in the asymptomatic population. [3] It is also believed that in most people the TMJ adapts to the disc position and rarely causes pain from being in a different position. [4]

Clinically Relevant Anatomy

See TMJ anatomy

Also see muscles of mastication

Clinical Presentation

Symptoms

• Pain or discomfort associated with any or a combination of: chewing, yawning, talking, bruxism [5]
• Headaches
• Ear pain
• TMJ range of movement may be restricted
• Crepit/click during jaw movement
• Pain or discomfort can be acute or chronic and may fluctuate in intensity.
• Emotional issues such as depression are often associated with TMJ pain

Symptoms may last from hours to days.

Red flags

1. Neurological signs
2. Swelling
3. Nose bleeding
4. Dysphagia or dysarthria
5. Unexplained weight loss
6. Auditory complaints
7. Constant pain unrelated to jaw movement

Types of TMJ disc displacement

[6]

1. Disc displacement reduction (DDWR)[1][7]: When the mouth is opened, the disc is displaced anteriorly to the condyle and the disc is repositioned on the head of the condyle.
   • Hear and palpate joint noises during opening and closing
   • Prominent opening and closing stop clicking each other
   • Unlikely to cause any restrictions on the ROM due to the puck moving when the mouth is opened
2. Disc displacement with intermittent locked reduction [1][7]: Same as DDWR, but with the additional symptom of intermittent limited jaw opening. This happens when the disc doesn’t shrink.
3. Disc displacement with limited patency (DDwoR): [1][8] Displacement of the disc without reduction.
   • TMJ pain
   • Limited jaw range of movement <40mm
   • Click and Eject 4. Disc Displacement Without Reduction No Restriction Open: Same as DDwoR without Restricted ROM, although Restricted ROM has to happen at some point.

The stages are under review and the new classification system is being trialled, but so far it has only been trialed in adolescents. [9] This classification reports five stages of disc displacement based on MRI findings.

Yang’s classification of TMJ disc advancement in adolescents

stageDiscCondyleMarrowStage 0Basic shapeNormal condylar shape and heightNormal volume and qualityStage 1Basic shape Mild and partial condylar resorption, but normal condyle height is reduced in the top part Stage 2Basic shape Moderate condylar resorption reduces condylar height. Slightly reduce Stage 3 Basic shape or distortion Severe condylar bone resorption moderate reduction 3A Basic shape maintenance or mild distortion and shortening Minor but moderate reduction in basic shape 3B Severe distortion and shortening Small but moderate reduction in basic shape Stage 4 Basic shape or severe distortion Moderately reduced condylar resorption with inflammatory changes or severely reduced or absent 4A Basic shape maintenance or distortion. Piercings are common. Severe resorptive loss of cortical bone integrity. Moderately reduced 4B basic shape retention or distortion with severe inflammatory changes. perforation Common Severe absorption or complete absorption Severely reduced or absent

[9]

Diagnostic Procedures

Evaluation of disc displacement can be done by subjective assessment, objective assessment, and radiography. [10]

Subjective assessment

The patient may have the history of:

• Insidious or traumatic onset
• Difficulty chewing food
• Reduced mouth opening
• Subjective clicking and popping

Objective Assessment

• Pain on TMJ palpation[11]
• Potential clicking on jaw opening
• Reduced TMJ range of movement
• Associated neck and facial muscles are tense, such as the sternocleidomastoid, upper trapezius, and masseter muscles.

Radiography

• XR[12]
• Ultrasound can be used to assess the degree of disc disorder
• MRI is considered gold standard

Management/Intervention

Disc displacement without reduction

The optimal treatment options for disc displacement without reduction are still under discussion and more evidence is needed because treatment is usually based on experience rather than evidence. [13][8]

Interventions can range from conservative treatment to surgical intervention. Although the primary management of disc displacement should always be conservative. [14]

Conservative treatment (mainly physical therapy)

1. Education and self-management[8]
2. Splinting
3. Therapeutic exercise
4. Joint mobilization of TMJ and cervical spine
5. Active jaw exercises and strengthening
6. Cognitive behavioural therapy
7. NSAIDs and analgesia

Surgical intervention

1. Arthrocentesis[15]
2. Arthroscopy
3. Open joint intervenetion

In the analysis of surgical interventions, outcomes (pain and TMJ range of motion) did not change when compared with each other. [8]

Clinical bottom line

Unreduced disc displacement will improve over time regardless of intervention, so optimal treatment will be the least invasive and most cost-effective, ie, educated self-management and early TMJ manipulation. [8] In some extreme cases, surgical intervention may be required But should be used as a last resort.

Differential Diagnosis

• Cervical spine disease coexists with TMJ disease in 70% of cases, so regular screening and treatment of the cervical spine is important [10]
• TMJ osteoarthritis
• See TMD