Imaging - Key Points Flashcards
What do x-rays show?
Bones
What do CT scans show?
Bones in more detail
Some soft tissue structures e.g. lumbar discs
What do MRI scans show?
Bones in less detail Bone marrow Discs Ligaments Spinal cord and nerves (i.e. all soft tissue structures)
What imaging modalities show bones?
X-rays
CT
MRI
What imaging modalities show soft tissues?
CT
MRI (especially)
Where does the neural foramen lie on the vertebrae?
Inferior to the pedicle
Name of the joint that forms between the articular processes of 2 adjacent vertebrae?
Facet joints
How does C1 vary from the other vertebrae?
No vertebral body
How does C2 differ from the other vertebrae?
Has an odontoid process (projects superiorly into C1 forming a joint with its anterior arch)
When is CT used to image spinal trauma?
X-ray show fracture -> more details required, ? any more fractures present
X-ray normal but high clinical suspicion of fracture
What does abnormal vertebral alignment on x-ray or CT imply?
Ligament damage and an unstable spine
Why type of imaging can be used to directly see intervertebral ligaments?
MRI
Colour of normal and abnormal ligaments on MRI?
Normal = black Abnormal = light
When is MRI used to image spinal trauma?
To provide detail of the spinal ligaments
In patients with neurological deficit which is not explained by x-ray or CT -> to show soft tissue abnormality e.g. acute prolapsed IV disc, epidural haematoma, spinal cord damage
What unique features about bony tumours of the spine can MRI tell you (in comparison to x-ray and CT)?
Bone marrow infiltration
Extradural mass
Spinal cord compression
What mode of imaging is best for viewing the IV discs?
MRI (CT can also be used but not as good)
What is the only imaging modality which adequately shows the spinal cord?
MRI
What are the 4 main (broad) causes of spinal cord disease?
Trauma
Demyelination
Tumour
Ishcaemia
Are x-rays useful in patients with sciatica?
No
What are the 2 main roles of imaging in arthritis?
Making diagnosis
Monitoring disease activity and response to treatment
Is OA joint involvement normally symmetrical?
No
What leads to sclerosis of subchondral bone in OA?
Increased subchondral bone cellularity and vascularity excites bone turnover leading to sclerosis
Wha causes joint deformity in OA?
Weakened bone caves in
Is RA normally symmetrical?
Yes
What spinal levels can RA affect?
C1/ C2
What causes soft tissue swelling in RA?
Synovial proliferation and reactive joint effusion
What causes periarticular osteoporosis in RA?
Hyperaemia causing bone demineralisation
What detroys bone at the joint margins in RA?
Inflammatory pannus
What leads to subluxation and deformity in RA?
Capsular and ligamentous softening
What can cause ankylosis (bone fusion) in RA?
Exposed eroded bone ends
What seronegative arthritis tends to affect the small joints of the hands and feet as well as DIP hints, IP joint of great toe?
Psoriatic arthritis
What seronegative arthritis tends to cause scattered lower limb large joint arthritis and lower limb entheses?
Reiters Syndrome
What type of scan cause show increased vascularity around joints which accompanies synovitis?
Isotope bone scan (allows RA to be diagnosed before joint damage occurs)
What scan can be used to show thickening of synovium and increased blood flow within it?
Colour Doppler Ultrasound
Purpose of MRI of inflammatory joint disease?
Can show periarticular bone marrow oedema which often precedes significant joint erosion/ damage -> early evidence of joint disease
How many x-ray views of trauma are often required?
2
What 2 areas require more than 2 views of trauma x-raying?
Cervical spine
Scaphoid
What are the 3 views required for trauma x-raying the cervical spine?
AP
Lateral
Odontoid peg (AP with mouth open)
What are the 4 views required when x-raying the scaphoid?
AP
Lateral
2 obliques
How to tell if a bony entity is an evulsion fracture or a mimic?
Avulsion fracture is incompletely corticated unlike a mimic which will be surrounded in dense cortex
What are 3 examples of avulsion fracture mimics?
Sesamoid bones
Accessory ossification centres
Old non-united fractures
What are sesamoid bones?
little bones that sit at joints lubricating the passage of tendons
What is the posterior fat pad sign a sign of?
An elbow effusion -> trauma is a common cause of an effusion (always abnormal -> sensitive indicator of elbow trauma)
What is another name for a grow plate?
Physis
What type of classification is used to trade growth plate fracture?
Salter Harris classification
What is the weakest part of a developing bone
Growth plate
What does a femoral fracture of a baby suggest?
NAI
What material of foreign bodies can be seen on x-ray?
Metal and glass
What material of foreign bodies can’t be seen on x-ray?
Plastic and wood
What tends to cause focal pathological fractures?
Metastatic deposit
What tends to cause diffuse pathological fractures?
Osteoporosis
Other metabolic bone disease
What type of fracture would an elderly patient with osteoporosis get from a FOOSH?
Colles fracture
What type of fracture would a child get from a FOOSH?
Radial buckle fracture
What type of fracture would a young man get from a FOOSH?
Scaphoid fracture
What type of fracture would a post-menopausal female get from a FOOSH?
Surgical neck of the humerus fracture
What type of x-ray view would show a posterior shoulder dislocation?
Oblique view
How many patients will be dead 1 year following a proximal femoral fracture?
20-35% (46% over 80 years)
What imaging modality provides detailed information about undisplaced fractures?
MRI (can see bone marrow)
What type of imaging can provide high resolution images of superficial soft tissue structures?
US
MRI also provides high resolution images of soft tissue structures including those deep (which US struggles with)
Typical lower limb sites of impacted fractures?
Femoral neck
Tibial plateau
Clacaneus
Whites the primary imaging type of all polytrauma patients?
CT scan
Best imaging for assessment of pelvic soft tissue injury?
MRI
What commonly causes acute pelvic soft tissue injury?
Muscle tear
Tendon avulsion
Typical direction of acetabular fracture?
Posterior (with acetabular rim fracture)
Complications of hip dislocation?
Femoral head AVN
Early OA
What complications are intra-capsular proximal femoral fractures prone to?
AVN
Non-union
How is intra-capsular proximal femoral fractures treated?
hemiarthroplasty
Unless undisplaced or young patient = reduction and screw fixation
How is extra-caspular proximal femoral fracture treated?
Internal fixation with DHS
What should you do if high clinical suspicion of proximal femoral fracture but x-ray normal?
Repeat x-ray after 10 days or immediate MRI
2 main risks with a femoral shaft fracture?
Blood loss
Fat embolus
What is lipohaemarthrosis a specific sign of?
Intra-articular fracture of knee
What type of imaging and plane may show a lipohaemarhtrosis?
Horizontal beam lateral x-ray
What condyle do most tibial plateua fractures affect?
Lateral condyle (due to values force with foot planted -> “bumper injury”)
What imaging modality is good for showing extensor tendon injuries?
US
What imaging modality is used to visualise intra-articular soft tissue knee injuries?
MRI
Standard ankle x-ray planes?
AP
Lateral
What is the posterior malleolus?
Posteroinferior tibia
What type of ankle fracture can excessive in/eversion cause?
Talar dome margin fractures
What imaging modality can diagnose a talar dome margin fracture which is invisible on x-ray?
MRI
How is the central peak of the normal calcaneus measured?
Using Bohler’s angle
What is located at the base of the 5th metatarsal in adolescents?
Accessory ossification centres
What is normally seen along the posterior calcaneus in children?
A fragmented ossification centre
What is the name of the sesamoid within the lateral head of the gastrocneumius (often visible posterior to the distal femur)?
Fabella
What is the name of the accessory ossification centre often seen posterior to the talus?
Os trigonum
What is often the best imaging modality for assessing ankle tendon injury?
US (can also use MRI but less comfortable for patients)
What plane is used to assess 1st and 2nd TMT joint congruity?
AP view
What plane is used to assess 3rd to 5th TMT joint congruity?
Oblique view
