MSK Radiology 2 and 3

Question 1

Describe a system for the interpretation of musculoskeletal anatomy:

Answer 1

• S ‐ Soft Tissues
• A ‐ Alignment – luxation, fracture, congenital
• B ‐ Bone – cortex & medulla, trabeculae in metaphysis and epiphysis
• C ‐ (Cartilage) = Physes (do with the bone)
• C ‐ (Cartilage) = Joint (System for joints too)
• D ‐ Device = Orthopaedic device

Question 2

Describe how bone should be systematically evaluated:

Answer 2

• Epiphysis ⇒ epiphysis: Epiphysis ⇒ physis ⇒ metaphysis ⇒ dipahysis ⇒ metaphysis ⇒ physis ⇒ epiphysis
• Cortex ⇒ cortex: Periosteum ⇒ cortex ⇒ endosteum ⇒ medulla ⇒ endosteum ⇒ cortex ⇒ periosteum

Question 3

How does the appearance of the distal ulnar physis compare between cats and dogs?

Answer 3

• Cats = flat
• Dogs = appears much more cone shaped

Question 4

What are the two main responses that bone has to disease?

Answer 4

1. Increase in bone or bone production
2. Decrease in bone - osteolysis or bone loss re-absorption

Question 5

What are the three main things that need to be determined when interpreting bone to make a radiographic diagnosis?

Answer 5

1. Benign or aggressive process
2. Activity (hazy or sharp)
3. Age or chronicity (opacity)

Question 6

How is lesion activtiy determined?

Answer 6

Based on margins:

• Active lesion = hazy, poorly defined margins
• Old inactive lesions = sharp, well defined margins

Question 7

Is the lesion shown below aggressive or benign?

Answer 7

• Aggressive - significant transition zone size
• Also know it is active due to hazy and poorly defined margins

Question 8

Is the lesion that is shown below aggressive or benign?

Answer 8

• Benign - also know it is inactive - sharp well defined margins are seen

Question 9

Define the term transition zone, what is an indicator of and compare the transition zone of lesions A and B below:

Answer 9

• Transition zone = transition (distance) between abnormal and adjacent normal bone - the wider the transition zone the more aggressive the lesion is (transition zone is an indicator of aggression)

A: aggressive lesion - it is poorly defined and irregular (A has a much wider transition zone than B does)

B: non-aggressive lesion - sharp in outline and is smooth

Question 10

Describe the chronicity of the three lesions that are shown below:

Answer 10

• A: Chronic lesion - chronic similar to the underlying cortex
• B: Poorly mineralised - hence we know that this lesion is active and fresh
• C: Chronic lesion - also the same opacity as the underlying cortex

Question 11

What are the three main patterns of lysis that produce a focal radiolucency (rank them in order or their agression)?

Answer 11

1. Geographic lysis (Least Aggressive)
2. Moth eaten lysis (Aggressive)
3. Permeative lysis (Most Aggressive)

Question 12

Name the type of lysis shown below:

1. Describe the 7 features that are seen
2. Provide a radiological diagnosis
3. provide 3 ddx

Answer 12

Geographic lysis:

7 features:

1. Single or multiple areas of radiolucency
2. Lesion margins: sharp to slightly hazy (activity) or smooth to slightly irregular (aggresion)
3. Bone @ lesion margin: sclerotic short distance
4. Adjacent bone is normal
5. Cortex can be normal, expanded or thinned
6. No evidence of cortical destruction
7. Secondary pathological fractures may be present

Radiographic diagnosis:

• Benign or non-aggressive lytic lesion

Ddx:

• Bone cyst
• Abscess
• Bacterial osteomyelitis

Question 13

Name the type of lysis that is shown below:

Answer 13

Benign geographic lysis:

• Left = involcrum/abscess
• Right = bone cyst

Question 14

Name the pattern of lysis that is shown below and:

1. Describe how the margins appear
2. How to cortex appears
3. How the adjacent bone appears
4. How the transition zone appears
5. What are the main Ddx for this lesion

Answer 14

Moth eaten lysis:

1. Margins appear irregular and poorly defined
2. Cortex normally destroyed
3. Adjacent bone is abnormal
4. Transition zone is wide + poorly defined

Main Ddx:

1. Neoplasia
2. Mycotic osteomyelitis
3. Bacterial osteomyelitis (less likely)

Question 15

Name the pattern that is shown below and provide three Ddx for the appearance:

Answer 15

Moth eaten lysis pattern:

1. Neoplasia
2. Mycotic osteomyelitis
3. Bacterial osteomyelitis (less likely)

Question 16

Name the pattern of lysis that is shown below and describe how it appears:

Answer 16

Permeative lysis:

Multiple small pinpoint areas of lysis - bone appears porous and has patchy irregular pattern to trabecular markings. Very poorly defined edges (lysis).

Question 17

What is the radiographic diagnosis for permeative lysis and what are two differentials?

Answer 17

Ddx: Very aggressive and destructive lesion

2 main Ddx:

1. Usually an infiltrative neoplasm
2. Fungal osteomyelitis = much less likely

Question 18

What is the lag phase for the formation of new bone?

Answer 18

• Lag phase of 7-10 days for production of new bone

Question 19

Below is an example of smooth solid homogenous new bone formation:

1. What are some differentials for periosteal new bone formation? (give 3)
2. What are three differentials for endosteal new bone formation? (give 3)

Answer 19

Periosteal new bone formation:

1. Periostitis
2. Focal trauma (splint)
3. Normal healing fracture callous
4. Chronic low grade osteomyelitis
5. Inactive old lesion

Endosteal new bone:

1. Endosteal callous
2. Panosteitis (young)
3. Boen infraction

Question 20

Name the bone healing pattern that is shown below and provide 4 Ddx for it:

Answer 20

Laminar, lamellar, multilayers or onion skin:

• Repetitive trauma
• Chronic episodic osteomyelitis
• Slow growing neoplasia
• Fracture Healing

Question 21

Name the pattern of new bone that is shown below and provide 4 Ddx:

Answer 21

Irregular solid periosteal new bone Ddx:

1. Osteomyelitis
2. Hypertrophic osteodystrophy
3. Hypertrophic osteopathy (HO)
4. Unstable fracture repair/complicated fracture repair

Question 22

Describe how agressiveness can be determined from the interupted new bone pattern:

Answer 22

1. Spiculated
2. Sunburst
3. Amorphous pattern

Short and fat (palisading) ⇒ long and thin (spciulated) - the longer, thinner and more disorganised the spicules the more aggressive the lesion is

Question 23

Define palisading:

Answer 23

Short and fat

Question 24

Define spiculated:

Answer 24

Long and thin appearance

Question 25

Define the term lysis with regards to the trabeculae:

Answer 25

Coarse and the fine trabeculae are destroyed

Question 26

How is osteoporosis seen in regular trabeculae?

Answer 26

Coarse trabeculae are seen and fine are reabsorbed

Question 27

How is sclerosis typically seen within the trabeculae?

Answer 27

Seen as an increase in the thickness of the trabeculae and a decrease in size of intertrabecular spaces and increased opacity

Question 28

Provide a minimum of three features that are indicative of an aggressive lesion:

Answer 28

• Aggressive lysis (moth eaten)
• Aggressive New Bone (spiculated)
• Cortical destruction
• Poor demarcation of lesion margin
• Wide transition zone
• Rapid change over time

Question 29

Provide three features that may be seen in a non-aggressive lesion:

Answer 29

• No lysis or benign form
• No new bone or smooth solid
• Well demarcated margin
• Short transition zone
• No or little change over time