Trauma Imaging of Lower Limb Flashcards
what is used to show complex features of a fracture if X ray isn’t enough?
CT
MRI or US if soft tissue
why is a lower limb fracture more dangerous than upper limb?
higher risks dehydration and starvation DVT and PE pneumonia much higher death rate, esp if elderly
limitations of X rays?
overlapping of anatomical structures (not in CT)
some fractures invisible if either not shown or not displaced
doesn’t show soft tissue injury
how can limitations of X ray be overcome?
CT
not affected by these limitations as its cross sectional
MRI gives info about bone marrow so can show un displaced fracture, can also show deep soft tissues
US can show superficial soft tissues
why are fractures visible?
as the gap is filled with haematoma so is less dense than bone on X ray
common fracture appearences?
fine lucency across normal bone
displacement
impacted sclerotic bone
where is impacted fracture common?
tibial plateau fracture
calcaneal fracture
hip?
what is the typical presentation of pelvic ring injury?
young people
RTA or fall from a height
usually multiple (affect more than one site - SI joints, pubic symphysis)
how is high energy pelvic injury imaged?
X ray if only site of injury
CT if multiple sites or to get more detail of pelvic injury
who gets low energy pelvic ring injury?
elderly patients with osteoporosis
due to minor fall or insidious onset
imaging for low energy pelvic ring injury?
MRI > CT > X ray
usually multiple injuries
what causes pelvic soft tissue injury?
sports injury
usually, acutely, due to muscle tear or tendon avulsion
chronic overuse
common pelvic dislocation story?
RTA
contact sports where hip is flexed
typically posterior with acetabular rim fracture
imaging for pelvic/hip dislocation?
CT
classification of proximal femoral fractures?
intracapsular
extracapsular
intracapsular fractures?
interfere with blood supply to femoral head
prone to femoral head AVN or non-union
how is an intracapsular proximal femoral fracture treated?
hemiarthroplasty
unless undisplaced or young patient when reduction and screw fixation may be tried
how is proximal femoral fractures imaged?
can be invisible on X ray so if high suspicion
- repeat X ray after 10 days
- immediate MRI
what causes femoral shaft fracture and what are the risks?
high energy
blood loss
fat embolism
assessment of knee?
clinical exam X ray CT MRI/US usually soft tissue, fractures are rarer
what can a small avulsed bone fragment indicate in the knee?
significant soft tissue injury
what usually accompanies a significant soft tissue injury in the knee?
effusion which fills suprapatellar space
made of blood etc
standard knee trauma X ray?
AP
horizontal beam lateral (shows lipohaemarthrosis, blood and fat in suprapatellar recess which is a specific sign of intra articular fracture)
knee dislocation on imaging?
significant soft tissue disruption
potential for vascular injury
often largery reduced by time of X ray
what causes a tibial plateau fracture?
usually affects lateral condyle
valgus force with foot planted
tibial plateau fracture imaging?
CT
best imaging for extensor mechanism injury?
US
best imaging for intr-articular soft tissue injury (e.g meniscal tear)?
MRI
what can cause knee locking?
displaced meniscal tear
bucket handle meniscal tear
imaging for hyaline cartilage injury?
MRI - can show extent of injury, any loose bodies and assess surgical repair
risk with hyaline cartilage injury?
early OA
why are tibia or fibular fractures usually accompanied by another fracture?
as they form a bony ring
what usually causes ankle injury?
inversion or eversion
ankle assessment?
examination - check for soft tissue swelling
imaging
- check bony alignment
non uniform ankle joint space?
indicates instability often with ligamentous injury
describe malleolus fractures?
may be solitary
in which case they are often small avulsion fractures or undisplaced
trimalleolar fractures?
medial. lateral and posterior malleolus all affected
imaging for complex ankle fractures?
CT
3 other sites of ankle fracture?
talar dome (excessive inversion or eversion)
- best diagnosed via MRI as can be invisible on X ray
5th metatarsal (inversion injury)
- can resemble lateral malleolar
- transverse
calcaneous (falling from height onto heel)
- loss of central peak and increased bone density
what can mimic fractures in lower limb?
accessory ossification centres sesamoid bones (fabella behind knee. at 1st metatarsal head)
what can predispose to ankle tendon rupture?
diabetes
RA
steroid use
common midfoot injuries?
TMT joint (Lisfranc)
describe Lisfranc injury?
loss of congruity between metatarsal bases
often accompanied by ligamentous avulsion fractures
what are the features of an extracapsular proximal femoral fracture?
doesn’t affect blood supply to the femoral head so doesn’t cause AVN or non union
how is an extracapsular proximal femoral fracture treated?
internal fixation using DHS
