TMJ Imaging

Question 1

using plain film
- pros and cons

Answer 1

pros
- readily accessible
- low radiation dose

cons
- limited imaging

Question 2

panoramic radiography
- pros and cons

Answer 2

pros
- readily available
- quick
- comfortable for patient
- sectional views

cons
- sensitive to positioning errors
- superimpositioning of structures and ghost images
- doesn’t exclude early bone changes
- doesn’t image soft tissue component

• only a fronto-lateral view of the condyle - 2D image rather than 3D
• inconsistent magnification and geometric distribution

Question 3

CT scans
- pros and cons

Answer 3

pros
- structures can be assessed without superimposition
- can assess osseous structures and ankylosis

cons
- can’t see the articular disc

Question 4

4 indications and 3 contra-indications for an OPT for TMJ?

Answer 4

• displaced - occlusion, mandible, movement range
• recent trauma

CI
- joint noises
- myofascial pain
- ortho treatment (don’t take image just for TMJ)

Question 5

what radiographs are taken to assess the TMJ?

Answer 5

• plain film
• OPT
• PA (postero-anterior) mandible
• Reverse Townes (X-ray beam is 30 degree down and behind the patient head)
• CT

Question 6

what trauma can occur to the TMJ?

Answer 6

• fracture
• dislocation - condyle displaced out of glenoid fossa but within the joint space

Question 7

what type of TMJ dislocation is most common?

Answer 7

anterior dislocation
- condyle is anterior to articular eminence
- patient can’t close their mouth

Question 8

do you need imaging for dislocation?

Answer 8

no

Question 9

what is Subluxation of the joint?

Answer 9

= partial dislocation
patient has large range of movement
- condyle can go beyond the articular eminence, more than usual but can slip back into place comfortably

Question 10

what are the planes of the body?

Answer 10

sagittal - down the middle - left and right (side to side)
coronal - down the middle - front and back
transverse - through the middle - up and down

Question 11

describe an MRI and the two sequences.

Answer 11

a giant magnet with radio waves producing an image

T1 - weighted-fat bright

T2 - weighted-water bright

Question 12

what is the only imaging where you can assess the articular disc position and status?

Answer 12

MRI

Question 13

MRI
- Indications

Answer 13

• assess disc position and status prior to surgery
• assess presence of synovitis in inflammatory arthritis

Question 14

what is the most common disorder in the TMJ?

Answer 14

Myofascial Pain Syndrome

Question 15

Myofascial Pain Syndrome
- definition
- is the joint affected?

Answer 15

muscle tension, fatigue or spasm leads to pain in MoM (can be from bruxism)

• the joint is not affected

Question 16

Internal Derangement
- defintion
- symptoms

Answer 16

displacement of disc from normal position
- most common is anterior

symptoms
- clicking
- trismus
- pain from the joint
- can be with (returns to OG) or without reduction (doesn’t return to OG) on opening

Question 17

Degenerative Joint Disease
- definition
- what happens
- symptoms
- imagine features

Answer 17

non-inflammatory
- due to ‘wear and tear’
- from sustained microtrauma

• articular cartilage deteriorates
• bone exposure
  = condylar head flattens and bone defects

symptoms - can be asymptomatic
- painful crepitus
- trismus

imaging features
- flattened articular surface
- erosion
- decreased joint space
- sclerosis - increased density
- osteophytes - bony projections @ site of muscle attachment, can fracture off
- subchondral cyst - collection of fluid beneath the articular surface

Question 18

how does bone appear on a CT vs MRI/

Answer 18

CT - lighter
MRI - dark

Question 19

what is the relation between Internal Derangement and Osteoarthritis?

Answer 19

high correlation

Question 20

describe Rheumatoid Arthritis
- how does it image with the TMJ?

Answer 20

synovial membrane is inflamed
get secondary bony erosion
- get a granulomatous tissue growth in synovium

TMJ
- condylar head is eroded like a sharp pencil

Question 21

describe Juvenile Idiopathic Arthritis
- how does it image with the TMJ?

Answer 21

onset is <16 years

synovial inflammation
- chronic and intermittent

TMJ
- flat, deformed condyle
- wide glenoid fossa

Question 22

what is Joint Effusion?

Answer 22

collection of fluid in the joint space

Question 23

Condylar Hyperplasia
- definition
- signs

Answer 23

developmental large condyle with normal morphology

signs
- facial asymmetry

Question 24

how can you differentiate Condylar Hyperplasia from a Osteochondroma?

Answer 24

osteochondroma does not enlarge
the ipsilateral half of the mandible