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AC1 (Izzy) > Medical Imaging: Joints > Flashcards

Medical Imaging: Joints Flashcards

1
Q

What is lipohaemoarthrosis?

What is it indicative of?

A

Fat and blood in a joint

Indicative of an intra-articular fracture

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2
Q

What does this xray indicate?

A

Lipohaemoarthrosis:

  • Effusion beneath patella - straight line above femur
  • ‘FBI’ sign: fat-blood interface sign

Fracture to tibial head

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3
Q

What causes lipohaemarthrosis?

A

Fatty marrow separates from the blood (water based) which gives the characteristic fat-fluid level indicated by the straight line on the xray.

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4
Q

What types of imaging can be used when a higher sensitivity is needed to image a joint?

What can they identify?

A

CT and MRI

Can identify haematocrit effect:

  • Fat
  • Synovial fluid
  • Blood
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5
Q

Name 3 common joint emergencies seen on imaging

A

Lipohaemarthrosis

C-spine injury

Joint dislocation

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6
Q

What indications may there be for spinal imaging?

A

Trauma

Malignancy

Infection: TB, discitis, abscess

Disc prolapses

Degenerative changes

Limb pain (neuropathic)

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7
Q

What imaging modalities may be used for a suspected c-spine injury?

A

X-ray

CT

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8
Q

What is the first line imaging used for suspected cauda equina syndrome?

A

MRI

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9
Q

What imaging modality should be used for suspected discitis?

A

MRI

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10
Q

In what circumstances may nuclear imaging of the spine be indicated?

A

Malignancy

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11
Q

Describe the method of interpreting a C-spine x-ray

A

Adequecy (all cervical vertebrae visible? and ideally top of T1)

Alignment: are the lines smooth? Are there any bony prominences outside of the lines?

  • Anterior vertebral line
  • Posterior vertebral line
  • Spino-laminar line
  • Posterior spinous line

Bones: are the borders of the cortex of each bone smooth?

Cartilage: are the spaces between the vertebrae uniform?

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12
Q

When imaging joints, why would a CT scan be used over x-ray?

What can CT scan not exclude in terms of joints?

A

Higher sensitivity

In trauma situations where x-ray appears normal

If x-ray shows an abnormality, to further investigate

Cannot exclude ligamentous injury

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13
Q

What are the benefits of using MRI?

What type of tissue can they show?

A

Higher sensitivity

Can see ligaments, nerves and soft tissue

Can look closely at individual nerves: demyelination

No radiation compared to CT and MRI

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14
Q

WHat type of imaging can be used to investigate suspected demyelination?

A

MRI

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15
Q

What does this MRI show?

A

Prolapse of lumbar vertebral disc causing spinal cord compression

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16
Q

What does the MRI show?

A

Discitis causing obliteration of the disc and damage to the vertebral bodies above and below.

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17
Q

Why might neck positioning for intubation in a patient with RA be potentially fatal?

What should be performed before intubation for RA patients?

A

Asymptomatic C1/C2 disease in rheumatoid arthritis patients

Routine radiographic evaluation should be performed for patients with RA going for procedures that involve neck manipulation.

18
Q

Where is the most common site of spinal injuries?

Why is this?

A

C-spine (particularly C1 and C2)

Flexible, exposed part of the spine

19
Q

What is atlanto-occipital dislocation?

What damage does it cause?

A

= Ligamentous separation of the spinal column to the skull base

Pure flexion injury: usually results in instant death, also known as ‘internal decapitation’.

  • Damage to brain stem and spinal cord
  • Dissections of carotid and vertebral arteries

Survivors usually have irreversible tetraplegia

20
Q

How is atlanto-occipital dislocation diagnosed?

A

CT

If either BAI or BDI >12mm usually suggests AO dislocation.

Wackenheim line: straight line extending from posterior clivus through the dens (normal situations should not intersect the dens)

21
Q

What is an atlanto-axial dislocation?

What are the degenerative and traumatic causes?

A

Dislocation of C1 from C2

Degenerative:

  • Rheumatoid arthritis (c-spine third most common place for RA to affect)
  • Down’s syndrome

Traumatic:

  • C1/C2 fractures
  • Transverse ligament injuries
22
Q

What are the potential symptoms of c-spine damage in a person with RA?

A

Quadriparesis

Altered consciousness/drop attacks

Lhermitte’s phenomenon

Neck pain

Respiratory dysfunction

Dysphagia

23
Q

When may plain radiographs be used for C1/C2 imaging?

Which 2 views can be used?

A

Non-trauma cases only

Open-mouth odontoid view

Flexion and extension views (should only be done after open-mouth odontoid views have excluded odontoid fracture or severe subluxation)

24
Q

What should be calculated in an open-mouth odontoid radiograph?

A

Sum of lateral mass displacement, if >6mm combined may indicate lateral ligament injury

25
Q

What should be measured in flexion and extension views of C1/C2 radiographs?

A

ADI: atlanto-dens interval: distance between odontoid process and the posterior border of the anterior arch of atlas.

  • >3.5mm = unstable

SAC: space available for cord: distance from the posterior surface of dens to anterior surface of posterior arch of atlas.

  • In RA, >14mm = high risk of cord injury
26
Q

What distance between the odontoid process and posterior border of the anterior arch of atlas is considered unstable?

A

>3.5mm

27
Q

What is a Jefferson fracture?

How is it caused?

Is it a stable or unstable fracture?

A

C1 burst

Due to vertical compression force through the occipital condyles into the lateral mass of atlas. Caused by inferiorly directed forces on top of head (e.g. diving into swimming pool)

Forces drive the lateral masses of C1 outwards causing fractures of the anterior and posterior arches +/- disruption of the transverse ligament.

Highly unstable

28
Q

What is a hangman’s fracture?

How is it caused?

Stable or unstable?

A

C2 pedicle fracture

Hyperextension injury

Unstable

29
Q

How is a C2 odontoid fracture caused?

What are type I and type II odontoid fractures?

How is it best seen on x-ray?

A

Forceful flexion or hyperextension

Type I: occurs above the transverse ligaments

Type II: occurs below the transverse ligaments, at the base of the peg. Most common.

Best seen on open-mouth odontoid view

30
Q

According to the Canadian C-spine rules, when is imaging of the C-spine required?

A

Age 65 or above

Dangerous mechanism

Paraesthesias in extremities

Inability to rotate neck 45°

31
Q

What imaging modality should be used in children <16 if there is a strong suspicion of:

Cervical spinal cord injury

Cervical spinal column injury

A

MRI

32
Q

When should plain x-ray be used in children under 16 for c-spine imaging?

A

When they do not fulfil criteria for MRI (strong suspicion of cervical spinal cord or column injury based on Canadian C-spine rules and clinical assessment) but there is still clinical suspicion after assessment.

33
Q

When should CT be used for suspected spinal injury in adults?

When should MRI be used?

A

When imaging is recommended by Canadian C-spine rules

Strong suspicion of thoracic or lumbosacral spinal injury associated with abnormal neurological symptoms.

MRI should be used after CT if there is neurological abnormalities which could be attributable to spinal cord injury

34
Q

Define joint dislocation

A

Abnormal seperation in the joint where 2 or more bones meet

35
Q

Which imaging modality is usually used for suspected dislocations?

Which views are required?

A

Plain radiograph

Anterior view and lateral view

36
Q

What type of dislocations are the most common?

What should also be considered when looking at this type of dislocation?

A

Shoulder- particular anterior dislocations

Hill-Sachs and Bankart lesions, AC joint disruption and acromioclavicular fracture should also be looked for.

37
Q

What type of shoulder dislocation is this?

What other imaging should be used to confirm this?

A

Anterior shoulder dislocation

Side view radiograph should be used to confirm as could be posterior dislocation

38
Q

What type of shoulder dislocation is this?

Why?

A

Posterior

Humeral head is to the left of the normal position

39
Q

What type of shoulder fracture is this?

Why?

A

Anterior dislocation

Humeral head is to the right of the normal position

40
Q

What are Hill-Sachs and Bankart’s lesions?

What are they caused by?

A

Hill-Sachs: posterolateral humeral head compression fracture, typically secondary to recurrent anterior shoulder dislocations, as the humeral head comes to rest against the anteroinferior part of the glenoid.

Bankarts: injuries specifically at the anteroinferior aspect of the glenoid labral complex, and represent a common complication of anterior shoulder dislocation

41
Q

What is ultrasound useful for identifying?

What do bilateral findings suggest?

A

Effusions

Bilateral: may indicate systemic arthritis disorder or transient synovitis.

42
Q

What are the advantages and disadvantages of using MRI in children?

A

Advantages:

  • Highest resolution
  • Good for muscular and ligamentous injuries

Disadvantages:

  • Degraded by motion: most children will need sedation

AC1 (Izzy) (48 decks)

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