Anatomical landmarks of the joint
To understand the radiological picture and pathologies of the TMJ on tomograms, key anatomical elements are distinguished:
- Articular tubercle of the temporal bone (tuberculum articulare ossis temporalis).
- Articular disc (discus articularis).
- Condylar process of the mandible (processus condylaris mandibulae or mandibular head).
The lateral pterygoid muscle attaches to the articular disc, and its correct position and biomechanics are critical for the function of the entire maxillofacial system.
MRI capabilities in disc displacements
Magnetic resonance imaging is indispensable for diagnosing internal joint derangements, as conventional radiographs do not show soft tissues:
- Subluxation (initial form): Anterior displacement of the articular disc is observed with its subsequent reduction within the fossa. Patients experience clicking when opening and closing the mouth, and dynamic MRI records the restoration of the correct position.
- Recurrent dislocation: The ligaments lose the ability to hold the disc, and it blocks the movement of the mandibular head. During a blocking episode, MRI clearly visualizes anterior irreducible displacement.
- Chronic dislocation: The ligaments of the bilaminar zone are irreversibly damaged, and the disc assumes a permanent anteromedial position, leading to limited mouth opening and pain syndrome.
Diagnosis of posterior dislocation and secondary changes
In addition to frequent anterior displacements, rare forms of pathology are encountered in clinical practice:
- Chronic posterior dislocation: With the mouth closed, the disc is located posterior to the condylar process. At the onset of movement, it becomes impinged between the mandibular head and the posterior surface of the mandibular fossa.
- Secondary osteoarthritis: Long-standing articular disc dislocation triggers progressive deformation of the articular surfaces of the condylar process and the articular tubercle. On MRI and radiographs, this reveals joint space narrowing, osteophytosis, and changes in bone structure.
MRI shows Soft Tissues: disc in place — no click, disc forward — expect a click or blockade.
Class and exam questions
What imaging method is used to examine the TMJ articular disc?
Magnetic resonance imaging (MRI) is used to assess the state of soft tissue elements and the articular disc.
What is the difference between subluxation and chronic dislocation of the articular disc?
In subluxation, the disc displaces with subsequent reduction and preservation of clicking. In chronic dislocation, the ligaments are irreversibly damaged, the disc is permanently displaced, and it blocks jaw movements.
What clinical symptoms are characteristic of chronic articular disc dislocation?
Pain, a sensation of a mechanical obstruction, mandibular deviation, and limited mouth opening with an interincisal distance of less than 2.5 cm are noted.
What else to study on this topic
- Radiological and functional signs of TMJ osteoarthritis and arthritis
- Differential diagnosis of acute TMJ arthritis
- Anatomical features of the maxillofacial muscles in joint pathologies
- Etiology of facial asymmetry in children with TMJ osteoarthritis
- Clinical picture of TMJ lesions in dental malocclusion
Master the entire topic in the course "Surgical Dentistry"
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "TMJ MRI" and 866 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 28 video lessons on the subject
Other topics in "Chapter 13. Temporomandibular Joint Disorders (V.V. Bekreev)"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.