Radiology Flashcards
1
Q
Bones are shown by what scans?
A
- xrays (radiography)
- CT
- MRI
2
Q
Soft tissues are shown by what scans?
A
- CT
- especially MRI
3
Q
What are the normal spinal curvatures?
A
- cervical lordosis
- thoracic kyphosis
- lumbar lordosis
4
Q
The neural foramen lies inferior or superior to the pedicle?
A
Inferior
5
Q
Normal spinal anatomical features can be identified in which view?
A
Lateral view
6
Q
What scan is most sensitive for spinal fractures?
A
CT
7
Q
When is CT used to image spinal trauma?
A
- xray shows fracture but more detail required, ?any more fractures present
- xray normal but high clinical suspicion of fractures
8
Q
Describe intervertebral ligaments
A
- ligaments tether vertebrae together and are responsible for spinal stability
- ligaments are not seen on xray or CT but seeing normal vertebral alignment on these test implies intact ligaments and a stable spine
- abnormal vertebral alignment on xray or CT implies ligament damage and an unstable spine
9
Q
Ligaments are only seen directly on which scan
A
- MRI
- normal ligaments are black on MRI scans
- damaged ligaments are light on MRI
10
Q
When is MRI used to image spinal trauma?
A
- occasionally to provide detail of the spinal ligaments
- in patients with neurological deficit, which is not explained by xray or CT, to show soft tissue abnormality such as; acute prolapsed intervertebral disc, epidural haematoma, spinal cord damage
11
Q
Describe the imaging features of vertebral tumours
A
- xray and CT findings; bone sclerosis (increased bone density), bone destruction (reduced bone density), vertebral collapse (pathological fracture)
- unique MRI findings; early (bone marrow infiltration), late (extradural mass and spinal cord compression)
12
Q
Describe imaging intervertebral discs
A
- discs are invisible on xrays
- xrays may show disc space narrowing but this correlates poorly with symptoms of sciatica
- CT shows lower lumbar disc prolapses
- MRI is best, showing all disc prolapses and even the disc dehydration which precedes this
13
Q
The spinal cord is only adequately shown by what?
A
MRI
14
Q
Name some intrinsic causes of spinal cord disease
A
- demyelination
- ischaemia
- MRI may be used to detect this
15
Q
What is the role of imaging in arthritis?
A
- to detect features of disease in order to make a diagnosis and monitor disease activity and response to treatment
16
Q
Describe the radiographic features of OA
A
- in healthy joints, hyaline cartilage creates a lucency between corticated bone ends on xrays
- this is referred to as the joint space
- in OA, asymmetric cartilage wear leads to asymmetric joint space reduction
- increased subchondral bone cellularity and vascularity drives new bone formation leading to sclerosis of subchondral bone, seen as an increase in bone density
- synovial fluid dissects into bone, forming cysts
- periosteal stimulation leads to marginal osteophyte formation
- weakened bone caves in, resulting in gross joint deformity
17
Q
Describe diagnostic features of RA
A
- synovial proliferation and reactive joint effusion cause soft tissue swelling
- osteopenia; hyperaemia causes bone demineralisation resulting in periarticular osteoporosis
- erosion; inflamed thickened synovium (pannus) destroys bone, initially at the joint margins
- marginal erosion is the hallmark of RA
- with time, bone erosion progresses, spreading across the joint
18
Q
Describe RA deformity
A
- erosion ‘shortens’ the bones, producing lax ligaments and joint capsule
- inflammation softens ligaments which stretch further
- joint subluxation and deformity develop
- tendon failure may exacerbate this
19
Q
Describe ankylosis of RA
A
- exposed eroded bone ends occasionally fuse
- ankylosis is much more typical sero-negative arthritis
20
Q
Seronegative arthritides are characterised by what?
A
- synovitis (inflammation of joint and tendon sheath linings)
- enthesitis (inflammation at sites where ligaments and tendons attach to bone)
21
Q
Name characteristic distribution and radiographic features of seronegative arthritis
A
- sacroiliac joint and spine involvement
- ill defined periarticular new bone formation
- tendency to ankylosis of ligaments and across joints
22
Q
For which areas of the body is two views required?
A
- cervical spine; AP, lateral, odontoid peg
- scaphoid; AP, lateral, two obliques
23
Q
What is a comminuted fracture?
A
Three or four fragments
24
Q
Describe impaction fractures
A
- axial forces through the bone, bone appears denser than normal
25
In what ways can fracture appearance is variable?
- lucency crossing bone
- cortical expression
- spiral / transverse
- comminution
- joint involvement
- angulation
- displacement
- impaction
- avulsion
26
Name some avulsion fracture mimics
- sesamoid bones
- accessory ossification centres
- old non-united fractions
27
Describe the posterior fat pad sign
- fat density may be seen anterior to the distal humerus on normal xrays, as shown opposite
- if an elbow effusion is present, and trauma is a common cause of an effusion, a displaced fat pad becomes visible posterior to the distal humerus, the posterior fat pad sign
28
Describe pelvic soft tissue injury
- sports related pelvic soft tissue injury is common
- acutely, this is typically due to muscle tear or tendon avulsion
- chronic overuse can cause bone or soft tissue pain at site of tendon or ligament attachment
- US can show acute injuries affecting superficial structures
- MRI is imaging method of choice as it provides more complete assessment of all soft tissues and bones
29
Is a visible posterior fat pad abnormal or normal?
Always abnormal
30
Name some examples of bony rings
- spinal canal
- pelvis
- forearm and lower leg
31
Why might there be a skeletal weakening leading to a pathological fracture?
- focal as in the metastatic deposit causing a clavicle fracture
- diffuse due to osteoporosis or other metabolic bone disease
32
What view should you obtain for posterior shoulder dislocation?
- when the humerus dislocates posteriorly, the lack of displacement makes it difficult to appreciate on an AP xray
- an oblique view (on right) should always be obtained, and shows abnormal humeral displacement posterior to the articular surface of the glenoid
33
Describe intra-capsular fractures
- interfere with blood supply to femoral head prone to femoral head AVN or non-union typically treated by hemiarthroplasty
34
Describe extra-capsular fractures
- don't affect blood supply to femoral head don't get femoral head AVN or non-union treated by internal fixation using DHS
35
A standard trauma xray series for knees comprises what?
- AP
| - horizontal beam lateral
36
Describe tibial plateau fracture
- 80% affect lateral condyle, following valgus force with foot planted ('bumper injury')
- variable appearance, from obvious fracture line to subtle subchondral sclerosis
- the area of condylar involvement / depth of depression guides treatment, and is well shown by CT
37
Describe knee soft tissue injuries
- acute intra-articular soft tissue injuries may also be difficult to assess clinically due to swelling and pain
- these are well shown y MRI, which has become a common test in acute knee trauma
38
What can MRI show for knee soft tissue injuries?
- meniscal tears
- cruciate, collateral or other capsular / ligamentous injuries
- hyaline cartilage damage
- subtle fractures
39
What is the usual injury mechanism for ankles?
Inversion or eversion
40
What type of ankle fractures have a particular tendency to instability?
Trimalleolar fractures
41
Describe 5th metatarsal base fractures
- follows inversion and clinically resembles
42
Describe calcaneal fractures
- usually follows axial compression, such as falling from height onto the heel
- calcaneal compression fracture causes loss of bohers angle and increased bony density
43
What is the os trigonum ?
An accessory ossification centre commonly seen posterior to the etalus
44
Where are rounded sesamoid bones found?
- may arise at multiple sites within the foot, but ar invariably present on the medial and lateral plantar aspects of the 1st metatarsal head
45
How is complete from partial tears distinguished?
Possible with US or MRI
