W2: Imaging of the musculoskeletal system Flashcards
What types of scans are commonly used to image MSK problem?
X-ray
CT
MRI
Ultrasound
Bone scan (inject radioactive tracer into blood stream and use to detect tumours)
Bone density scan
What is the use of an x-ray in MSK imaging?
Uses electromagnetic radiation
Gives information on tissue desnity
Good for differentiating and positioning bone, air, liquid and soft tissue.
Gives basic detail information
Identifies fractures, dislocation, arthiritis, cancers etc - large visible changes in strucutres
What information can x-rays not tell use about an MSK injury?
What should we use instead in each instance?
Unable to identify soft tissue injury (MRI or CT)
Subtle fractures (CT)
Exact type of malignancy or grade (biopsy)
What is important practically when ordering an x-ray?
Obtain at least two views eg anterior and lateral
View should include two joints adjacent to the injured bone
May request view of unaffected limb to assess symmetry in children
May consider further iimaging (CT or MRI) for occult fractures of soft tissue injury
What are some difference types of fractures?
Spiral
Oblique - oblique break
Transverse - straight transverse break
Complex/comminuted -
Wedge
Impacted
Displaced
Open/compound
What is a spiral fracture?
Bone is broken from a twisting motion
Fracture line wraps around the bone in a corckscrew like motion
What is an oblique fraction?
Break line is oblique
What is a transverse fracture?
Break line is transverse
What is a complex/comminuted fracture?
Broken into multiple pieces, multiple break points
What is a wedge fracture?
Common in the spine from compression and flexion
result in one piece fully disconnected from the rest of the bone
The remaining bone is often not attached to each other
What is an impacted fracture?
When broken ends of bone are jammed together by force of injury - often cause broken pieces to fragment
Compression of the bone
May also be called a buckle fracture - are most common in children as they are still growing.
What is the difference between a displaced and a dislocation fracture?
Displaced - bone is broken and because of break has moved into the wrong place
Dislocation - bone is not broken but has moved into the incorrect anatomical position
What is meant by an open/compound fracture?
Open wound
Bone pokes out of the skin
What details should be given when describing an x-ray?
Patient demographics
What is the x-ray of?
What is the view of the x-ray?
What does the x-ray show?
Suggest what type of fracture? - where, intra or extraarticular, displaced.
What are the different types of fracture displacement?
Angulation - point loss of shared long axis
Rotation - rotated along shared axis
Change in bone length
Loss of alignment (can overlap with other types)
How can fractures be classified by their location to the joint surface?
How does this affect treatment plan?
Is fracture is on the joint surface is considered intraarticular
If avoids the joint surface is extraarticular.
Intra-articular fractures are more likely to require surgical intervention
What are the direct signs of a fracture on an x-ray?
A subtle lucent or sclerotic line through bone.
Show deformity
Show separated fragments
What are the indirect signs of a fracture of an x-ray?
Callus formation (periosteal reaction)
Effusion (simple of fat level) - appear as greyish soft tissue with overlying blackish area then greyish area again - creates a clear line in soft tissue image - lipohemoarthosis
soft tissue swelling
What is important to remember on a safeguarding note about fractures?
Consider the age of the patient
Consider the general well being/appearance of patient and family/friend dynamic
Does the type of fracture/appearance of fracture on imaging align with the patient history
How do hip fractures commonly present clinically?
Normally elderly patients
Leg is normally shortened and externally rotated following a fall
What is the basic radiographical order for a x-ray of a hip after a fall?
Anterior to posterior of whole pelvis including both hips
Lateral projection of the injured hip/ hip of interest
What is Shentons line in x-ray imaging?
An arch like shape seen on an anterior posterior view of the pelvis
Drawn between the medial edge of the femur and the inferior border of the superior pubic rami
Demonstrates a normal x-ray
What are the different sites of proximal femur fracture?
Extracapsular - pertrochanteric
Intracapsular - subcapital, cervical, basal
Why is the location of a femur fracture important clinically?
Relates to blood supply to the head of the femur
An extracapsular fracture - blood supplt the head of femur is normally maintained by the capulsar retinacula artery (alongside ligamentum teres vessels) - so no bone necrosis so hip replacement is not needed - Screws and wiring sufficient
An intracapsular fracture - interupt blood supply to the head of the femur (supply from ligamentum terest is insufficient) necoris of femor head is likley so requies half hip replacement minimum.
How can the bladder be imaged on CT?
In what MSK injury scenario might you want to do this?
Use a catheter to insert dye into bladder - normal should get one balloon shape in pelvis, if abnormal spreading out from this shape may be seen
Often request is trauma to the pelvis - if multiple fractures to pelvis particularly pubic rami as in very close proximity to bladder.
What are the advantages of using CT in MSK imaging?
Quick
Great for fracture configuration and surgical planning - as high detail and potentially 3D model
Multisystem imaging (bones and soft tissue, so can view many body systems at once)
Good for interventional practise
What are the disadvantages of CT is MSK imaginge?
Radiation - more concerning in children
Low detail on soft tissue
What is a panscan?
Also called a trauma CT or whole body CT
Head to toe CT scan - typically done on trauma patients with multiple injuries
What are the advantages of MRI in MSK imaging?
High amounts of detail of soft tissue.
Can alter sequencing e.g T1 or T2 to better highlight different structures
No radiation - safer for children
Good imaging of tumours
Good imaging for the spinal cord
What are the disadvantages of using an MRI for MSK imaging?
Relies of the patient lying still for a long period of time - difficult in children or if clasutrophobic
Long acquisition time - poor in emergency trauma
Patients with pacemakers or metal componenets may not be able to have a scan.
What conditions are commonly identified on an MRI scan?
ACL tear
Cauda equnia syndrome - intervertebral disk compression on cauda equina - weakness in lower limb and loss of bladder control
Bone tumours
What are the advantages of ultrasound in MSK imaging?
Dynamic imaging (changes when looking at it)
Cheap
Mobile
used for intervention
No radiation/claustrophpbia
Good for soft tissue
What are the disadvantages of using ultrasound for MSK imaging?
Very user dependent
Limited detail in image
Poor for imaging bone
Acoustic shadows can make it harder to image certain structures.
How does a rotator cuff tear appear on ultrasound?
Loss of tendon continuity
Tear area (absence of tendon) appears black.
What type of scan is shown?
What does is show?
Bone scan
Darkened areas indicate areas of metastasis
What type of interventional procedures may require imaging as well?
Guided biopsy - normally ultrasound
Guided injections - place needle into joint then inject a contrast fluid to insure in the correct joint then may use to inject medications/anaesthetic. - normally a CT or an MRI
