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Musculoskeletal > Trauma Imaging of Lower Limb > Flashcards

Trauma Imaging of Lower Limb Flashcards

1
Q

What are lower limb fractures associated with?

A

High morbidity and mortality

Immobility = pneumonia, DVT/PE, dehydration/starvation

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2
Q

What are the limitation of x-rays when imaging fractures?

A

Can’t visualise through overlapping structures
May not be shown on standard x-ray projection
Fracture is undisplaced
Can’t capture soft tissue structures

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3
Q

Why are CT scans useful for imaging fractures?

A

Cross sectional = unaffected by overlapping structures and can show fractures irrespective of their plane

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4
Q

Why are MRI scans useful for imaging fractures?

A

Provides detailed info about bone marrow so can show undisplaced fractures

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5
Q

What techniques can be used to image soft tissue injuries?

A 
US = high resolution images of superficial structures, especially tendons
MRI = high resolution images of all structures, even those deep inside body or within joints (areas where US struggles)
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6
Q

What are some features of lower limb fractures?

A

Often involve axial force with bone impaction = may appear sclerotic
Typical sites of impacted fracture = femoral neck, tibial plateau, calcaneus

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7
Q

What are some features of high energy pelvic ring fractures?

A

Often young people, associated with RTA or fall from height

Bony ring disruption usually affects more than one site so usually multiple (either bones of symphysis)

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8
Q

How are high energy pelvic ring fractures imaged?

A

X-ray if pelvis is only site of injury

CT is primary test for polytrauma patients

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9
Q

What are some features of low trauma pelvic fractures?

A

Affect elderly patients with osteoporosis, typically due to minor fall or may be of insidious onset
Multiple fractures often present = typically sacrum and pubic rami

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10
Q

How are low trauma pelvic fractures typically imaged?

A

X-rays often normal = CT better than x-ray especially once fractures start to heal
MRI is better than CT so is test of choice

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11
Q

What are some features of pelvic soft tissue injuries?

A

Sports related
Acute causes = muscle tear or tendon avulsion
Chronic overuse can cause bone/soft tissue pain at site of tendon/ligament attachment

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12
Q

How are pelvic soft tissue injuries imaged?

A 
US = shows acute injuries affecting superficial structures
MRI = gold standard, provides more complete assessment of all soft tissues and bones
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13
Q

What are some features of an acute hamstring tendon avulsion?

A

Commonly sports related, cause of acute pelvic injury

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14
Q

What are some features of a hip dislocation?

A

Result of RTA or contact sport where hip is flexed
Typically posterior, with acetabular rim fracture
May be complicated by femoral head AVN or early OA

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15
Q

How are hip dislocations imaged?

A

CT = details anatomy to help with surgical planning

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16
Q

What are the two classifications of proximal femoral fractures?

A

Intracapsular and extracapsular

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17
Q

What are some features of intracapsular proximal femoral fractures?

A

Interfere with blood supply to femoral head
Prone to femoral head AVN or non-union
Treated by hemiarthroplasty = young patients or undisplaced fractures may be fixed with reduction and screw fixation

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18
Q

What are some features of femoral shaft fractures?

A

Usually high energy and obvious on x-rays

Carry risk of blood loss or fat embolus

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19
Q

What kind of injuries are more common in the knee?

A

Soft tissue injuries

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20
Q

How is imaging used in knee injuries?

A

Ct used to clarify fracture anatomy

US and MRI used to assess soft tissue

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21
Q

What do small avulsed bone fragments indicate in the knee?

A

Significant soft tissue injury

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22
Q

What soft tissue structures are shown by the lateral view of the knee?

A

Patellar and quadriceps tendons

Suprapatellar fat space

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23
Q

What are significant soft tissue injuries in the knee normally accompanied by?

A

Effusion = fills the suprapatellar space

24
Q

What is the standard trauma x-ray taken for the knee?

A

AP (horizontal beam lateral) = can show lipohaemarthrosis which is a sign of an intra-articular fracture

25
Q

What are some features of a knee dislocation?

A

Often largely reduced by time of x-ray so check bony alignment
Results in complex soft tissue disruption
Has potential for vascular injury (popliteal artery)

26
Q

What are some features of a tibial plateau fracture?

A

80% affect lateral condyle
Follow valgus force with foot planted
Variable appearance = from obvious fracture line to subtle subchondral sclerosis

27
Q

How are CTs used to treat tibial plateau fractures?

A

Show are of condylar involvement and depth of depression which guides treatment

28
Q

What can be used to visualise extensor mechanism injuries of the knee?

A

US = clarifies quadriceps and patellar tendon tears

29
Q

What can be used to show acute intra-articular injuries of the knee?

A

MRI = can see through swelling

30
Q

What are some soft tissue injuries of the knee that MRI can be used to visualise?

A

Meniscal tears, capsular and ligamentous injuries, hyaline cartilage damage, subtle fractures

31
Q

What do the menisci of the knee do?

A

Spread load between femur and tibia

32
Q

What causes meniscal tears?

A

Twisting injuries = tear causes pain and can become displaced causing “locked knee”

33
Q

What do the ACL and MCL do?

A

Important stabilisers of knee

34
Q

What are some features of hyaline cartilage injuries?

A

Can predispose to early OA, invisible on x-rays

MRI can define extent of injury and any resulting loose bodies, as well as success of surgical repair

35
Q

What do the tibia and fibula form with the talus?

A

The paired bones form an elongated ring with the talus = disruption may be remote from each other

36
Q

How is the ankle normally injured?

A

Via inversion or eversion

37
Q

How are x-rays used in ankle trauma?

A

Part of initial assessment = AP and lateral views

38
Q

How are CT, MRI and US used in ankle trauma?

A

CT used to clarify fracture anatomy

MRI and US needed to define soft tissue injury

39
Q

Why do children get different fractures form adults?

A

The have growth plates and soft bones

40
Q

What does a non-uniform ankle joint indicate?

A

Instability = often has ligament damage

41
Q

What are some features of malleolar fractures?

A

Usually solitary, often small avulsion fractures or undisplaced

42
Q

How many views are undisplaced fractures usually visible on?

A

Only one

43
Q

What are some features of ankle fractures?

A

Often multiple, usually affect lateral and medial malleoli and posterior malleolus (posteroinferior tibia)

44
Q

What causes a talar dome margin fracture?

A

Excessive inversion or eversion = often subtle fracture invisible on x-ray, may need MRI to diagnose, cause of chronic pain and instability

45
Q

What are some features of a fifth metatarsal base fracture?

A

Follows inversion and resembles lateral malleolar fracture

Transvers = easily confused with normal adolescent longitudinal ossification centre

46
Q

What are some features of calcaneal fractures?

A

Follows axial compression = fall from height onto heel
Causes loss of peak (Bohler’s angle) and increased bone density, often comminuted
Anatomy clarified by CT

47
Q

What are some fracture mimics?

A

Accessory ossification centres and sesamoid bones

48
Q

What are some examples of accessory ossification centres?

A

Fifth metatarsal base = in teens, longitudinal ossification centre at base
Fragmented posterior ossification centre = normally seen along posterior calcaneus in children
Os trigonum = commonly seen on posterior talus

49
Q

What are some examples of sesamoid bones?

A

Fabella = within lateral head of gastrocnemius, often visible posterior to distal femur
Rounded sesamoid bones = found throughout, especially on medial and lateral plantar aspects of first metatarsal head

50
Q

What is the most common ankle tendon to be affected in an injury?

A

The Achilles tendon

51
Q

What may cause a tendon tear in the ankle?

A

Sometimes follows single high energy event

Often culmination of recurrent minor tears

52
Q

What are risk factors for ankle tendon injuries?

A

Diabetes, RA, steroid use

53
Q

What is used to determine between partial and complete ankle tendon tears?

A

US or MRI

US often easier for patients and allows dynamic assessment, especially of Achilles

54
Q

What are the standard views of the midfoot?

A

AP and oblique

55
Q

What are some features of TMT joint fracture/subluxation?

A

Subtle, can cause long term disability

56
Q

What is key to diagnosing TMT joint injury (Lisfranc)?

A

Alignment = assess first and second TMT congruity on AP view, and third to fifth TMT congruity on oblique view

57
Q

What are the characteristics of a Lisfranc injury?

A

Involve several TMT joints, with multiple ligamentous avulsion fractures = shown best by CT

Musculoskeletal (57 decks)

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