Radiology Of The Musculoskeletal System

Question 1

What are the advantages and disadvantages of radiographs/ x rays

Answer 1

+ quick
+ readily available and inexpensive
-involve radiation
-poor soft issue contrast resolution

Question 2

What is the role of radiographs(x rays) in the MSK imaging

Answer 2

1) intial imaging of choice for skeletal trauma/ acute bone or joint injury: fractures and joint dislocation
2) also used for chronic bone or joint pathologies. Eg chronic osteimyelitis ( infection of bone) , chronic arthritis e.g osteoarthritis and rheumatoid arthritis

Question 3

What are the different types of fractures

Answer 3

Transverse 
Linear 
Oblique nondisplaced
Oblique displaced 
Spiral 
Greenstick- on convex side of bone
Comminuted

Question 4

what is a fracture

Answer 4

complete or incomplete break in the continuity of bone

Question 5

what is a transverse fracture

Answer 5

break crosses the bone at a right angle to the long axis of the bone

Question 6

what is a linear fracture

Answer 6

fracture passes in parallel to the long axis of the bone

Question 7

what is a oblique fracture

Answer 7

fracture line is at an oblique angle to the long axis of the bone

Question 8

what is a compression fracture

Answer 8

axial load compresses cancellous bone beyond its limit

Question 9

name two fractures that only occur in children

Answer 9

greenstick fracture-incomplete fracture where bone bends and cracks. occurs in children younger than 10 because their bones are softer and more flexible
epiphyseal fractures-fracture line extends through an unfused growth plate, separating the epiphysis from the metaphysis

Question 10

what radiographic changes are seen in bones during childhood and what factors affect it

Answer 10

at birth there is a primary ossification centre in the diaphysis and a secondary one in the epiphysis. these are separated by epiphyseal plates. epiphyseal plates are less mineralised than bone so are less radio-opaque and can be seen on x rays as dark lines.
as the child grows the growth plates become thinner and eventually disappear.
factors influencing proliferation : GH promotes cellular proliferation but deficiency in thyroid hormone or excess corticosteroids result in less cell division leading to retarded growth.

Question 11

what is a bone age

Answer 11

a study that helps estimate the maturity of a child’s musculoskeletal system by looking at the degree of ossification of the carpal bones and the maturation of the growth plates of long bones.
significant difference between child’s bone age and their chronical age may indicate pathology such as precocious or delayed puberty , GH deficiency , hyper/hypothyroidism

Question 12

what are the 3 phases of fracture healing

Answer 12

inflammatory phase(hours to days) -haematoma formation, tissue death, inflammation/ cell proliferation 
reparative phase(days to weeks)-angiogenesis/granulation/procallus formation, soft(fibrocartilaginous) callus formation, hard callus formation.
remodelling phase (months to years)- fracture line will eventually become obscured and radiographic union is said to have occurred.

Question 13

advantages and disadvantages of CT

Answer 13

uses narrow x rays to produce slices of an object
+ better than x ray for soft tissues
+allows visualisation of different tissue densities within one slice
+excellent resolution
- motion artefact if patient moves
- exposure to higher radiation than x ray
- severely obese patients can’t be accommodated in the scanner
- patient may be allergic to intravenous contract and very rarely can cause anaphylaxis

Question 14

what units is density measured in a CT scan? what is the density f water in these units? what is the colour of anything more dense or less dense than water

Answer 14

hounsfield units (HU)
0HU
less dense or equal density is black.(air, fat,water)
more dense is grey/white 9soft tissue , bone)

Question 15

how does Magnetic resonance imaging work?

Answer 15

uses a strong magnet to generate a magnetic field in which the protons in H atoms line up Radiofrequency signal pulses are then applied to the tissue which deflects the protons. When the pulse is stopped the protons realign and emit a signal as they do so. This signal is detected and the data from this is used to create the three dimensional image.
better than CT and x ray for soft tissue but is poor at showing the micro-architecture of bone

Question 16

how are T1 and T2 images created in MRI

Answer 16

based upon the time in between repetition of the pulses and the strength of the pulse

Question 17

on a t1 weighted image how does fat and fluid appear

Answer 17

fat is bright and fluid appears dark

Question 18

on a t2 weighted image how does fat and fluid appear

Answer 18

both fat and fluid appear bright

Question 19

In a STIR sequence how does fat and fluid appear

Answer 19

signal from fat is supressed and appears dark whereas fluid appears bright

Question 20

advantages and disadvantages of MRI

Answer 20

+ no radiation
+good for soft tissues
+useful for generating multiplayer images
-magnetic metalwork can migrate through the body under the influence of the magnet causing injuries -non magnetic can also produce artefact
- longer imaging tine than CT
- very noisy claustrophobic patients don’t like it
- patients with implanted electronic devices cannot go into the magnetic field

Question 21

what is ultrasonography? advantages and disadvantages

Answer 21

uses high freq sound waves to produce images.
sound waves are produced by a transducer and travel through the patient. tissues and tissue planes deflect the waves back to the transducer and are then analysed to create an image.
+non-invasive , no radiation
+used on soft tissues
+locates fluid collections , target injections , aspiration of joints
+assesment of tendons and muscles
-highly skilled operator needed for interpretation of images
- resolution of deep tissues is poor
-limited sustainability for bone and intra articular imaging