Imaging lameness

Question 1

What are some indications for orthopaedic imaging?

Answer 1

Skeletal/joint pain
Acute/chronic lameness
Fracture confirmation/characterisation 
Swellings
Monitor/screening for inherited musculoskeletal disease
Metabolic bone disease
Evaluating systemic disease

Question 2

What is geometric distortion?

Answer 2

Distorted imaging on radiographs

Occurs if structure towards the edge of collimated area OR not parallel to plate

Question 3

How can geometric distortion be prevented?

Answer 3

Careful positioning - keep away from edge of collimated area, tight collimation, keep parallel

Question 4

What are the limitations of radiography?

Answer 4

Artefacts - e.g. Mack lines
Poor soft tissue contrast
2D image of 3D structures - structures superimposed

Question 5

What are Mack lines?

Answer 5

Lines of opacity
Not a real lesion (artefact)
Due to geometric distortion

Question 6

What is serial radiography?

Answer 6

Multiple radiographs over a period of time

To monitor disease progression or confirm a diagnosis

Question 7

What are the 5 Roentgen signs?

Answer 7

Number
Size
Shape
Location 
Opacity

Question 8

What amount of mineral loss (%) is required to see a reduction in bone opacity on a radiograph?

Answer 8

30-60%
Also takes minimum of 7 days to be apparent
Consider may be artefact
(Focal loss easier to detect)

Question 9

What may cause a generalised reduction in bone opacity on a radiograph?

Answer 9

Artefact

Nutritional issue - secondary to hyperparathyroidism

Question 10

Why does hyperparathyroidism cause a reduced bone density?

Answer 10

Increased parathyroid hormone

Causes calcium to be released from bone stores

Question 11

What may cause a focal area of decreased bone density?

Answer 11

Lysis - due to neoplasia or osteomyelitis

Question 12

What are the 3 types (patterns) of focal bone lysis?

Answer 12

Geographic
Moth-eaten
Permeative
(From least to most aggressive)

Question 13

What does monostotic and polyostotic mean?

Answer 13

Monostotic = affecting 1 bone
Polyostotic = affecting more than 1 bone

Question 14

How can skeletal lesions be categorised?

Answer 14

Focal or generalised
Symmetrical or asymmetrical
Monostotic or polyostotic

Question 15

Is cartilage visible on radiographs?

Answer 15

No - (soft tissue opacity)

Question 16

Give examples of subchondral defects

Answer 16

Osteochondrosis
Aseptic necrosis
Septic arthritis
Erosive arthritis
Soft tissue neoplasia
Trauma (avulsions) 
Osseous cyst-like lesions
Severe osteoarthritis

Question 17

What is an osteophyte?

Answer 17

Abnormal bony projection around joints

Bone spur

Question 18

What is an enthesophyte?

Answer 18

Abnormal bony projections at the attachment site of a ligament

Question 19

Joint effusions may not be distinguishable from periarticular swellings - except for which joint?

Answer 19

Stifle - adjacent fat provides contrast

Question 20

What may be seen radiographically with osteoarthritis?

Answer 20

Periarticular new bone at predictable sites
Soft tissue swelling/effusion
Subchondral sclerosis
Narrowed joint space (if weight bearing or v severe)

Question 21

What can cause mineralised bodies on radiographs?

Answer 21

Accessory centres of ossification
Tendinopathies (incidental)
Osteochondral fragments (pathological)

Question 22

What are the predilection sites for osteochondrosis?

Answer 22

Caudal aspect of humeral head
Medial part of humeral condyle
Lateral femoral condyle
Medial trochlear ridge of talus

Question 23

What are the predilection sites for osteosarcoma?

Answer 23

Proximal humerus
Distal radius/ulna
Distal femur
Proximal tibia

Question 24

What frequency probe should be used for musculoskeletal ultrasound imaging?

Answer 24

Linear (high frequency) probe