Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medical Imaging > Imaging the Lower Limb > Flashcards

Imaging the Lower Limb Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards
1
Q

For what 3 general reasons might imaging of the lower limb be performed?

A
  • to confirm a clinical suspicion / diagnosis
  • to rule out important diagnoses / pathologies
  • to guide or evaluate management / treatment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

In what 4 scenarios are plain XRs of the LL requested?

In what circumstance are they first line?

A
  • if there is clinical suspicion of / to exclude a fracture
  • if there is clinical suspicion of / to exclude a dislocation
  • if there is clinical suspicion of inflammation / infection
    • e.g. septic arthritis, gout, OA, RA, osteomyelitis
  • they are first line in ongoing / worsening bony pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are plain XRs of the lower limb good for visualising?

What is required to make clinical decisions?

A
  • they are good for visualising:
  1. fractures
  2. dislocations
  3. joint spaces
  • …but more than one view of the area of interest is required
  • they can also reveal areas of thickening and thinning of bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In what 3 situations might CT of the LL be performed?

A
  • if X-ray is equivocal
  • if X-ray is normal but there is ongoing clinical suspicion
    • e.g. evaluating the midfoot for a Lisfranc fracture dislocation - which is difficult to see on plain XR
  • if detailed anatomical information is needed in complex fractures** and **surgical planning
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When might an MRI of the LL be performed?

A
  • MRI is performed to image soft tissues such as ligaments, tendons, muscle and cartilage
    • e.g. meniscal or cruciate ligament injuries of the knee
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the following features on an AP pelvic view?

A
  • the pubic symphysis is a cartilagenous joint that is very strong
  • the pubic rami form a ring around the obturator foramen
  • obturator internus and externus are on the inside and outside of this ring
  • the obturator vessels pass through the obturator foramen a they travel from the pelvis to the medial side of the thigh
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is significant about Shenton’s line?

A
  • it runs along the inferior aspect of the neck of the femur and superior pubic ramus
  • if this is not a solid line, it suggests there is a fracture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What injury is shown here?

In what group of people is it common and how can you tell how recent the fracture occurred?

A

fracture of the pubic rami

  • there are both superior and inferior fractures present here
  • Shenton’s line is disrupted
  • this injury is common in elderly patients as a result of a fall
  • these are old fractures as they have slightly sclerotic margins
    • this happens when there is an ununited fracture that hasn’t healed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What type of fracture is shown here?

Why is this classed as major trauma and what is the immediate treatment?

A

“open book” fracture

  • there is disruption of the pubic symphysis and the ligaments holding it there, causing the pelvis to “spring open”
  • common in motorcycle injuries
  • there is a risk of bleeding to death due to disruption to / tearing of the pelvic veins (not bleeding from the fracture)
  • the pelvis is held in place by external compression until the patient can reach theatre
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What type of injury is shown here?

What can cause this and why is it classed as major trauma?

A

vertical shear fracture (through sacroiliac joint & sacrum with diastasis of pubic symphysis)

  • on examination, one leg will be shorter than the other as one hip is higher than the other
  • there is a risk of rupture to the pelvic veins, which can result in bleeding to death
  • this usually happens in trauma where all of the force travels through one leg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What injury is shown here?

A

vertical shear fracture through the iliac joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is meant by a “hip” fracture?

Who do they tend to occur in?

A
  • a “hip fracture” is a fracture of the femoral neck or proximal femur
  • they tend to occur in elderly people after low energy trauma / falls
  • a hip fracture in a young / healthy adult would require high energy trauma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the standard views for a hip fracture?

How might there be rotation in a neck of femur fracture?

A
  1. AP
  2. lateral
  • the lesser trochanter is attached to psoas, so internal rotation occurs due to the unopposed pull of psoas on the fractured femoral neck
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the fovea of the femur?

What is the implication if this is injured in a hip fracture?

A
  • it is an oval-shaped dimple on the head of the femur
  • the ligamentum teres attaches to the fovea
  • if the blood supply through the ligamentum teres is disrupted, this can result in avascular necrosis of the femoral head
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is shown by the yellow line?

A

Shenton’s line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How can hip fractures be classified?

A
  1. intracapsular
  2. extracapsular
  3. trochanteric
  • this depends on whether the fracture occurs within or outside of the region of the joint capsule
  • a trochanteric fracture is extracapsule and occurs through the trochanteric region
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a subcapital fracture?

A
  • this is a fracture occurring just below the head of the femur
  • it is intracapsular as it occurs within the joint capsule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where can femoral neck fractures occur?

Are they intra- or extracapsular?

A

Transcervical:

  • a transcervical fracture occurs midway across the neck
  • this type of fracture is intracapsular

Basicervical:

  • a basicervical fracture occurs across the base of the neck
  • this can be intracapsular or just extracapsular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Where are trochanteric and subtrochanteric fractures found?

A
  • trochanteric fractures occur between / through the trochanteric region
  • subtrochanteric fractures occur below the trochanters
    • these are technically fractures of the proximal femoral shaft
  • these are both examples of extracapsular fractures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the risk associated with intracapsular fractures and how is this managed surgically?

A
  • in an intracapsular fracture, there is a risk of disruption to the blood vessels in this region
  • this can result in avascular necrosis and death of the head of the femur
  • a hemiarthroplasty is performed and the head of the femur is removed to eliminate this risk
  • extracapsular fractures do not have the risk of avascular necrosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the blood supply to the hip joint?

A

cruciate anastomosis

  • the profunda femoris gives rise to the medial and lateral circumflex arteries
  • the medial circumflex artery is the primary supply to the joint as it gives the branches that enter the joint capsule to supply the femoral head
  • there is also a contribution from the inferior gluteal artery (from internal iliac)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What can happen to the cruciate anastomosis in fracture of the femoral neck and what does this result in?

A
  • fracture of the femoral neck can tear the medial circumflex artery
  • this leads to loss of the blood supply to the head of the femur, resulting in avascular necrosis
26
Q

How could this fracture be described?

What precaution needs to be taken?

A
  • this is a subcapital fracture, which is intracapsular
  • as it is intracapsular, there is a risk of disruption of the blood supply to the femoral head
  • due to the risk of AVN, hemiarthroplasty needs to be performed
27
Q

How could this fracture be described?

How might this be surgically fixed?

A
  • this is a subtrochanteric fracture (proximal femoral) that is extracapsular
  • a dynamic hip screw is used in extracapsular fractures
  • some wires would also need to be used to hold the lesser trochanter in place
  • in an ideal scenario, bone ends are positioned together but are still able to move slightly as this stimulates fracture healing
28
Q

How could this fracture be described?

A
  • this is an example of a trochanteric fracture (extracapsular)
  • these fractures can go through, between or just below the trochanters
29
Q

What classification system is used for subcapital fractures?

A

Garden classification

Garden I:

  • incomplete subcapital fracture

Garden II:

  • complete but undisplaced fracture (normal trabecular lines across joint)

Garden III:

  • complete and partially displaced fracture (interruption of trabecular lines)

Garden IV:

  • complete and fully displaced fracture (interruption of trabecular lines)
30
Q

After constant pain in the hip and inability to weight bear, what would be a concern after seeing this XR?

A

occult fracture of neck of femur

  • these are not easily diagnosed on radiograph
  • if they are missed, the non-displaced fracture may become displaced
  • MRI is the best tool to diagnose occult fractures, but often CT is performed first as it is easier to request and much quicker
31
Q

What is shown in this image?

A
  • MRI has been used to identify an occult femoral neck fracture that is not visible on plain XR
32
Q

What are the following features of the femur?

In what group of people to femoral fractures tend to occur?

A
  • femoral fractures tend to occur following low energy falls in the elderly
  • massive forces are required to cause femoral fractures in young, healthy adults
33
Q

How could this fracture be described?

How does it need to be fixed?

A

transverse fracture through the shaft of the femur

  • there is overlapping of the fracture, which leads to shortening of the leg
  • it needs to be pulled apart before the ends are placed together and a plate or intermedullary nail is used to fix it
34
Q

How could this fracture be described?

A

spiral fracture of the femoral neck

  • a spiral fracture occurs as a result of a twisting force, creating a fracture line that wraps around the bone like a corkscrew
  • this is much more unstable and will slip more easily
  • it is more difficult to fix and will require a nail down the centre of the bone
  • this is likely to be a pathological fracture as the bone is permanently eroded and supple
35
Q

How could this fracture be described?

In what condition is this more likely to occur?

A
  • this is a comminuted fracture of the distal femoral neck
  • more likely to occur in osteopenia when the bone density is low
36
Q

What are the following features of the knee joint?

What component is NOT part of the knee joint?

A
  • the knee joint is composed of the femur, tibia and patella
  • the fibula is NOT part of the knee joint
37
Q

What are the following components of the knee joint?

A
38
Q

What is this view of the called?

When is it used?

A

skyline view

  • it is used to look at the patellofemoral joint and for dislocations
39
Q

What is shown here?

What anatomical feature is present to prevent this occurring and in what condition is this absent?

A

subluxation of the patella

  • the lateral condyle is larger than the medial condyle to prevent sideways dislocation of the patella
  • the pull on the patella is to pull laterally when straightening the leg
  • in hypoplasia of the lateral condyle, there is frequent dislocations of the patella
40
Q

What is shown in this image?

A
  • this is a normal horizontal beam lateral view
  • the patellofemoral joint can be seen
  • the quadriceps ligament and patella tendon can also be visualised
41
Q

What is shown in this image?

What does it imply has happened?

A

lipohaemarthrosis

  • this is the presence of fat and blood in an effusion
  • fat is lighter than blood so will float on top and produce a line between the 2 layers
  • this indicates an injury to the knee joint has caused leaking of fat and blood
  • this is usually an occult fracture or avulsion of a ligament that has pulled a small amount of bone off (e.g. cruciate ligament injury)
42
Q

What can be used to help guide decision making when deciding whether to image the knee joint?

A

Ottawa knee rules

  • patients aged >55
  • patients with isolated patellar tenderness
  • patients with fibular head tenderness
  • patients who are unable to flex the knee to 90o
  • patients who cannot weightbear (at least 4 steps) both immediately after the injury and at the time of examination
43
Q

What XR views of the knee are typically taken?

A
  • standard views are AP and lateral
  • a “skyline” view gives a view of the patella
44
Q

What type of fracture is shown here?

A

tibial plateau fractures

  • this involves a break in the cartilagenous surface of the knee joint
  • it is rare to only break the bone, and often the meniscus, ligaments, muscles, tendons and skin around the knee are also involved
  • they can be easily missed if subtle so be aware of tenderness over the tibial plateau / swelling of soft tissues
45
Q

How are the tibia and fibula usually fractured?

A
  • the tibia is usually fractured after a direct below or from a fall
  • the fibula is often injured in conjunction with the tibia - if one fracture is seen then look for the other
  • the fibula is often injured as a result of a twisting injury or by repeated stress
46
Q

What nerve can be injured in a fracture of the fibula?

Why should the fibula be examined when there is an ankle injury?

A
  • fracture of the fibular neck can injure the common peroneal nerve
  • the proximal fibula should be examined when there is an ankle injury as fracture of the medial malleolus can cause proximal fibular fractures via transmitted forces
47
Q

What are the features of this AP view of the ankle?

What feature is particularly important to check?

A
  • the fibula is always located laterally
  • it is important to look at the joint spaces / alignment at the mortise as the distance all the way around this should be equal
48
Q

What are the features of this lateral view of the ankle?

How can the calcaneum be changed in pressure injuries?

A
  • the calcaneum has a “honeycomb centre” that becomes flattened in pressure injuries
  • landing on the heel with a high impact leads to a crush fracture and loss of height
49
Q

How could this fracture be described?

A
  • fracture through the ditsal fibula (lateral malleolus) with soft tissue swelling
50
Q
A
51
Q

How could this fracture be described?

A
  • there is a fracture of the medial malleolus and through the shaft of the fibula
52
Q

How could this fracture be described?

Why would it be difficult to fix?

A
  • the fracture involves the medial malleolus, tibia and shaft of the fibula
  • the ankle mortise is abnormal as the distance all the way around is not equal
  • this is an example of an intra-articular fracture
  • as soon as the fracture goes into the joint, there is loss of congruity and it is difficult to fix back into alignment
  • intra-articular fractures also predispose to arthritis
53
Q

Ankle injuries commonly present to A&E, but what are most of these caused by?

When should the ankle be imaged?

A
  • most ankle injuries are inversion injuries resulting in ligament sprains
  • these are painful on weight-bearing and cause significant swelling around the lateral malleolus
  • the ankle should only be injured when there is suspicion of a fracture
  • the Ottoawa ankle rules help clinicians decide whether XR is necessary after ankle injury
54
Q

What are the Ottawa ankle rules?

A
  • the patient is unable to weight-bear for 4 steps both immediately after injury and at the time of assessment
  • or they have tenderness over the posterior surface of the distal 6cm (or tip) of the lateral or medial malleolus
55
Q

What do the Ottawa ankle rules state about when foot XRs should be taken in conjunction with ankle XRs?

A
  • there must be trauma to the midfoot and pain and
  • tenderness over the navicular or base of the 5th metatarsal OR
  • patient cannot weight-bear for 4 steps both immediately after the injury and at the time of assessment
56
Q

When should you consider a lower threshold for performing an XR?

A
  • patients who are difficult to assess properly (intoxicated, agitated, learning difficulties)
  • when severe swelling prevents proper palpation of the bones
  • if patients have reduced sensation or other “distracting” injuries
57
Q

What are the 3 most common ways in which the foot may be injured?

A
  • avulsion fractures of the 5th metatarsal
    • this happens when an inversion injury pulls the base of the MT off
    • the fibularis tendon attaches here
  • fatigue (“stress”) fractures of the metatarsals (usually 2nd or 3rd)
    • occurs when someone does a lot of walking
    • there is a periosteal reaction but often a fracture line is not seen
  • fractures of the phalanges
58
Q

When are the calcaneus and metatarsals usually fractured?

A
  • fracture of the calcaneus most commonly results from a fall from height directly landing on the heel(s)
  • the metatarsals tend to be fractured when heavy objects fall onto or run over the foot
59
Q

What are the bones of the foot?

A
  • green = medial, lateral and intermediate cuneiform bones
  • pink = navicular
  • blue = talus
  • yellow = cuboid
  • orange = calcaneum
60
Q

What are accessory ossicles and what are they often mistaken for?

A
  • they are extra bits of bone around the ankle that are a normal variation
  • they are often mistaken for fractures
  • they are well-defined bone with clear cortical margins around the outside
  • avulsed parts of bone tend to have poorly-defined margins (unless they are chronic injuries) and are likely to be tender
61
Q
A

Medical Imaging (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions