HEAD AND CERVICAL SPINE

Temporomandibular Joint (TMJ)

 

Anatomy and Function

• Movements: depression and elevation of the mandible (open and close), protraction and retraction of the mandible, lateral deviation of the mandible. Used for chewing, talking, and clenching your teeth to hold back a catty sentence. 

• Muscles: masseter, temporalis, internal ptyeroid (see facial muscles page for details)

• Bones: mandible (bottom jaw, the one that moves), maxilla (upper jaw, immovable)

• The mandible is attached to the maxilla via strong, fibrous ligaments (temporomandibular ligament) and the TMJ capsule. 

• The jaw is cushioned by an articular fibrous disc. 

 

Assessment

• Emergency Response: Patients with a jaw injury may suffer from additional injuries that complicates breathing. Upon first response, the clinician should check the patient's BAC's (breathing, airway, circulation) before beginning any other evaluation. Should any of the vitals be compromised, immediate activation of EMS is necessary.

• Observation: Is there obvious deformity? Does the jaw seem slack or laterally deviated? Swelling? Redness? Eccymosis?

• Palpation: Point tenderness, palpable deformity, crepitus, swelling

• Functional Testing: Can the patient perform all TMJ movements? Can they fit three fingers vertically between the front teeth? Do they have pain with movement? Can they clench their teeth? 

• Manual Muscle Testing: Put a tongue depressor between their front teeth and have them bite down. Try twisting the tongue depressor one way or another, testing the strength and seeing if they have pain with any motion.

• Goniometry

  • Depression: Use a tape measure and measure the distance between the two front teeth on the maxilla and mandible.

    • Norms: dependent on the person, at least 3cm.

  • Lateral Deviation: Have the patient bite down hard on a tongue depressor at both normal and laterally deviated positions

    • Norms: Dependent on person, should be equal and opposite

  • Protrusion: have the patient bite down hard on a tongue depressor at normal and protruding positions

    • Norms: Dependent on person, at least 1 cm. 

 

Potential Pathology