3 - Principles of Radiology in MSK

Question 1

What is the most commonly used medical imaging modality?

Answer 1

X-rays (plain radiographs)

Question 2

What are the advantages and disadvantages of X-rays?

Answer 2

Adv: - Quick and inexpensive

Disadv: - Radiation - Poor soft tissue contrast

Question 3

What is osteomyelitis?

Answer 3

Infection of the bone

Question 4

On an X-ray how do cortical and cancellous bone differ?

Answer 4

Cortical bone is denser and appears more white on the image than cancellous bone

Question 5

How does articular cartilage appear on an X-ray?

Answer 5

Articular cartilage is radiolucent so appears as a dark joint space

Question 6

What is a fracture?

Answer 6

Complete or incomplete break in the continuity of a bone

Question 7

What are the different types of fracture?

Answer 7

• Transverse
• Linear (sagittal)
• Oblique
• Spiral
• Greenstick
• Comminuted

Question 8

What is a transverse fracture?

Answer 8

Break across the bone perpendicular to the long axis

Question 9

What is a linear fracture?

Answer 9

• A fracture line that passes parallel to the long axis of the bone - AKA sagittal fracture

Question 10

What is an oblique fracture?

Answer 10

A fracture line at an angle oblique to the long axis of the bone but still within one plane

Question 11

What is a spiral fracture?

Answer 11

• Easily confused with an oblique fracture - The fracture line spirals round in multiple planes due to twisting of the bone

Question 12

What is a compression fracture?

Answer 12

• Occurs in cancellous bone when an axial load compresses the bone beyond its limit - Most commonly in lumbar vertebrae

Question 13

What is a greenstick fracture?

Answer 13

• Incomplete fractures where the bone bends and cracks on one side instead of breaking into pieces - Usually in children < 10yrs

Question 14

What is an epiphyseal separation fracture?

Answer 14

• The fracture line extends through and unfused growth plate - The epiphysis separates from the metaphysis
• Most commonly slipped capital femoral epiphysis (SCFE) of the femur

Question 15

What two fracture types occur specifically in children?

Answer 15

• Greenstick fractures - Epiphyseal separation fractures

Question 16

The ossification centre in the diaphysis is the ………… ossification centre

Answer 16

Primary

Question 17

The ossification centres in the epiphyses are the ………… ossification centres

Answer 17

Secondary

Question 18

How do the epiphyseal growth plates appear on an X-ray?

Answer 18

• Less mineralised than surrounding bone - Less radio-opaque - Easily seen on X-rays as dark lines

Question 19

Give examples of factors that influence the proliferation and transformation of cells in the epiphyseal growth plate.

Answer 19

• Growth hormone promotes cellular proliferation - Thyroid hormone deficiency and excess corticosteroids result in a reduction in cell division (growth retardation)

Question 20

How is a child’s bone age determined?

Answer 20

• Estimates the maturity of the musculoskeletal system by looking at the degree of ossification of the carpal bones and epiphyseal growth plates - Take an X-ray and compare to a standard atlas of bone development - Bone age given in years

Question 21

What does a significant difference between a child’s bone age and chronological age suggest?

Answer 21

Pathologies such as: - Precocious (early) or delayed (late) puberty - Growth hormone deficiency - Hypo- or hyperthyroidism - Malnutrition

Question 22

What are the four key stages of fracture repair?

Answer 22

• Haematoma formation
• Soft (fibrocartilaginous) callus formation
• Hard callus formation
• Remodelling

Question 23

Fracture healing occurs broadly in three phases. What happens in the first (inflammatory) phase?

Answer 23

Hours - days - Haematoma formation - Tissue death - Inflammation and cellular proliferation

Question 24

Fracture healing occurs broadly in three phases. What happens in the second (reparative) phase?

Answer 24

Days - weeks - Angiogenesis/granulation/procallus formation - Soft callus formation - Hard callus formation

Question 25

Fracture healing occurs broadly in three phases. What happens in the third (remodelling) phase?

Answer 25

Months - years - Gradual replacement of hard callus with mature bone - Fracture line becomes obscured (radiographic union)

Question 26

In CT scanning, tissue density is measured in what units?

Answer 26

Hounsfield units

Question 27

How does MRI work?

Answer 27

• Uses a magnetic field to line up protons in hydrogen atoms - Radio frequency pulses are applies to deflect the protons - Protons realign when the pulse is terminated and emit a signal as they do so (different tissues realign at different rates) - Signal is detected and used to make a 3D image

Question 28

Which of MRI and CT is better for: - Soft tissue imaging (e.g. malignancy or prolapsed disc)? - Bone architecture imaging (e.g. complex fractures)?

Answer 28

• Soft tissue imaging - MRI - Bone architecture imaging - CT

Question 29

How do T1 and T2 weighted MRI images differ?

Answer 29

T1 - fat is white, water (fluid) is dark T2 - fat and fluid are bright

Question 30

What is a STIR sequence in MRI?

Answer 30

• Fluid-sensitive sequence - Signal from fat is suppressed (appears dark), fluid appears bright - Useful for detecting oedema

Question 31

What is the most common contrast medium used in MRI? How is it given?

Answer 31

Gadolinium - Injected percutaneously into a joint or administered intravenously

Question 32

What is ultrasonography?

Answer 32

• Use of high-frequency sound waves to produce images - Sound waves made by a transducer and travel through the patient, tissues reflect the waves back and are analysed to create an image

Question 33

How is nuclear medicine used to image bone?

Answer 33

• Radioisotope-labelled, biologically active drugs given to the patient
• Marker of metabolically active bone (e.g. metastatic disease or healing fractures)