TMJ imaging Flashcards
What shape is the mandibular condyle?
Ellipsoid in shape
What is the name of the depression in the mandible where the pterygoid muscle attaches?
Pterygoid fovea
What is the articular disc made of? What is its shape? Where does it attach?
- Consists of fibro-cartilage and divides into upper and lower joint compartments
- Biconcave shape with a narrow middle
- Posterior band attaches to the retrodiscal tissues at the bilaminar zone
What are the two movements of the mandible called?
Rotation and translation
What images can we take to view the TMJ?
- Panoramic imaging, including open and closed views
- Cone beam CT
- Facial bone views e.g. PA condyles, reverse Townes – condylar neck
- CT – medical
- MRI – demonstrates the soft tissue components of the TMJ
- Ultrasound – limited application
- Nuclear medicine – shows bone activity
Is the condyle easier to see on X ray if the patient is open or closed?
Open
What are the + and - of DPT imaging of the TMJ?
+
Simple
Tomographic overcomes the problems of superimposition of right and left sides
Dedicated TMJ open and closed views
-
May not always show articular surface (superimposition)
Condyle seen obliquely and not as a true lateral
It lacks sharp details and so may not show subtle bony changes
Condyle imaged in the protruded position
Does not show the disk
How does a CBCT image work for the TMJ?
for TMJ imaging:
* Allows multiplanar thin section assessment
* Choose the smallest volume that adequately images the region of interest to for dose reduction
* Normally taken with the mouth closed
* Used to assess the osseous components of the TMJ, will not show the articular disc
* Helpful in assessing ankylosis, neoplasms, trauma and degenerative joint disease – not responding to treatment
What is Tmj hypoplasia and what condition is it common in?
mandibular condyle is smaller than normal
common unliterally
usually an associated mandibular asymmetry with a shortened ramus height
radiology:
* Condyle diminished in size
* Thin condylar neck
* Posterior aspect of the neck may have a backward curvature (arrowed)
* Ante-gonial notching at lower border due to reduced muscle activity
condition = hemifacial microsomia (reduced growth and development of the face)
What is condylar hyperplasia?
Developmental anomaly resulting in enlargement of the condylar head or an elongated condylar neck.
Typically, unilateral
More commonly affects females than males.
Apparent during the second decade of life.
The condyle continues to grow after puberty due to persistent growth of the condylar cartilage
Self-limiting condition but usually result in facial asymmetry
What is a bifid condyle?
Aetiology uncertain but it is probably developmental or possibly traumatic
It appears as a vertical depression/notch on condylar head
Usually often asymptomatic and so found usually as an incidental radiographic finding
May resemble a bony tumour, look for normal cortical outline and cancellous bone .
What is myo-fascial pain? it is managed radically or conservatively? are x rays needed?
Common condition, can be associated with stress, bruxism and may follow dental treatment.
Causes tenderness of the facial and neck muscles.
Conservatively managed, no X rays needed as pain in soft tissues.
How does internal derangement of the disc occur?
- The disc is anteriorly placed when the mouth is closed
- On opening, the disc either goes back to its normal position and causes a click (anterior displacement with reduction), or the disc remains anteriorly displaced (anterior displacement without reduction) with no click
Where does the condyle get positioned in mandibular displacement? What happens to the mouth position?
Position of condyle is anterior to the articular eminence but within the joint capsule.
What are some acute causes of TMJ dislocation?
What are some chronic causes of TMJ dislocation?
Acute = trauma, yawning, tooth extraction, prolonged rct
Chronic = neuromuscular imbalance, lax capsular ligaments, flat articular eminence
