Imaging the Upper Limb Flashcards
What are the 3 general reasons why the upper limb may be imaged?
- to confirm a clinical diagnosis / suspicion
- to rule out important diagnoses / pathologies
- to guide or evaluate management / treatment
- imaging should always be undertaken with a question in mind
In what 5 situations may plain XRs of the upper limb be requested?
- clinical suspicion of / to exclude a fracture
- clinical suspicion of / to exclude a dislocation
- to assess bone / joint after manipulation
- clinical suspicion of infection / inflammation - e.g. septic arthritis, OA, RA, gout
- ongoing / worsening bony pain suggestive of malignancy / other pathology / occult fracture (no history of trauma)
Why are plain XRs the first line investigation for imaging the UL?
- cheap, accessible, quick and basic interpretation is not too difficult
- they are good at identifying fractures, dislocations and joint spaces
- they can reveal areas of thickening or thinning of bone
- they are good for foreign body detection (e.g. glass in the hand which needs to be removed before suturing a wound)
What are the problems associated with plain XRs?
- exposure to ionising radiation
- caution should be taken in children, who tend to injure their limbs a lot
- ? too accessible
When might CT scanning be used in the upper limb?
- when detailed anatomical information is needed in complex fractures or for surgical planning
- when XR is equivocal
- when XR appears normal but there is ongoing clinical suspicion
When might MRI be used for imaging the UL?
- MRI is used to image soft tissues such as ligaments, tendons, muscles and cartilage
- e.g. rotator cuff tendons
- it is good for visualising bone bruising - there will be water present in the bone marrow
When is the shoulder imaged?
- if there is clinical suspicion of a dislocation of the humeral head (“shoulder”)
- if there is clinical suspicion of a fracture of the humeral head or neck
- it should also be included when imaging is primarily undertaken to view the clavicle (for suspected fracture or AC joint disruption) and the humeral shaft
Why is the shoulder joint prone to dislocation?
- it is a ball and socket joint, in which the ball is much larger than the socket and the socket is shallow
- this allows for a balance between stability and range of movement
- the shoulder joint is unstable and prone to dislocation
- there are stabilising factors at the shoulder to prevent dislocation - humeral labrum, rotator cuff muscles, ligaments
How many views are taken when imaging the shoulder / UL?
2 views and 2 joints
- you want to see 2 views of the area of interest to make sure that pathology is not missed
- and you want to see the bone located both above and below the area of interest
How is the penetration of the UL XR measured?
- you should be able to clearly see the bony cortex
- cortical bone is the tough outer layer, and the centre consists of cancellous bone that contains fat, bone marrow, vessels and nerve endings
- you should be able to see dense white lines on either side (cortical bone) and this is where fractures will be seen
What are the stages involved in interpreting a radiograph of the extremities?
- image ID - what is it and when was it taken?
- check patient ID
- assess technical adequacy
- orientation - is there a side marker?
- 2 views and 2 joints
- penetration - can you see the bony cortex?
- look for artefacts and foreign bodies (jewellery should be removed)
- assess the bony architecture by following bony outlines and be aware of overlap
- assess the periosteum
- look at the joints and articular surfaces
- look at the soft tissues
What 9 things need to be considered when describing fractures?
- location of the fracture
- is the fracture open or closed?
- severity - incomplete, complete or comminuted?
- orientation - e.g. transverse, spiral
- displacement - e.g. angulation, rotation
- is there articular involvement?
- is there an underlying bony abnormality?
- examine the periosteum - is it thickened, lamellated, spiculated / starburst?
- examine the soft tissues - fat pads, swelling, gas, potential nerve injury
What is the difference between an open and closed fracture?
- an open fracture is piercing the skin, whereas a closed fracture is not
- open fractures are associated with a risk of infection
What is the difference between a simple and comminuted fracture?
- in a simple fracture, there are only 2 “bits”
- in a comminuted fracture, there are lots of “bits”
How is orientation described?
What type of fracture is easier to fix and why?
a fracture can be transverse** or **spiral
- spiral fractures are harder to fix as the bone gets shorter
- the 2 parts of the fracture slide over each other due to the pull of muscles
- the bones need to be pulled apart before being fixed otherwise the bone will remain shorter
What is meant by articular involvement and why is it important to identify?
- this describes whether or not the fracture has gone into the joint
- if there is articular involvement, there will nearly always be arthritic change afterwards even if it is fixed
What type of fractures are shown here?
In what types of people do they occur?
- Buckle fracture and Greenstick fractures are incomplete fractures that only occur in children as their bones are still developing
Greenstick fracture:
- occurs when one side breaks and the other remains intact
- the bone bends and cracks, rather than breaking into 2 separate parts
Buckle fracture:
- involves buckling (abnormality) of the cortex, but it is not broken
- one side of the bone bends and raises a little buckle, without breaking the other side
What are these types of fracture?
- an avulsion fracture occurs when a tendon / muscle has pulled a bit of bone off
What are the 2 categories of periosteal reaction?
Non-aggressive:
- the bone remains well-defined
Aggressive:
- the bone becomes poorly defined and it is difficult to draw a line around it
What are the 3 types of non-aggressive periosteal reaction and when are they seen?
- thin
- solid
- thick irregular
- thick irregular periosteum is normal and happens soon after a fracture
- this turns into solid, followed by thin and then disappears
What are the 5 different types of aggressive periosteal reaction?
- lamellated (onion skin)
- spiculated (hair on end)
- spiculated (sunburst)
- disorganised
- Codman triangle
What is a Codman triangle?
- this occurs when the periosteum is so severely damaged that it cannot produce a full reaction
- it occurs in aggressive bone lesions
- the periosteum does not have time to ossify with shells of new bone in aggressive lesions, so only the edges of the raised periosteum will ossify
When is onion skin reaction seen?
Ewing’s sarcoma
- spiculated is seen in osteosarcoma / mets
What are the features of this AP shoulder view?
- yellow line = anatomical neck of humerus
- green line = surgical neck of humerus
- blue lump = greater tuberosity
- blue circle = lesser tuberosity
- purple = acromion
- yellow circle = glenoid fossa
- pink circle = acromioclavicular joint
- orange lump = corocoid process
- red lines = first rib and medial border of scapula
What is the “Y view”?
How can it be used to look for dislocations?
- the “Y” consists of the body, spine and acromion of the scapula
- the humeral head should sit over the meeting of the 3 lines
- if it does not, then there is likely to be dislocation of the head
What is an axial view?
What are the features?
- this looks from the top downwards
What sites can fractures of the proximal humerus occur at?
- head
- greater tubercle
- lesser tubercle
- surgical neck
- fractures of the proximal humerus can occur at one or more of these sites
Describe this fracture
- AP radiograph of a right shoulder that shows a fracture that is closed and comminuted (can see multiple parts)
Describe this fracture
- a simple fracture that is oblique and through the surgical neck of the left humerus
- there is slight displacement and rib fractures are also present
Describe this fracture
- comminuted fracture
- cannot comment on dislocation from a single view - the ball is still in the socket but the head of the humerus is lower than it should be
What is at risk when there is a fracture around the surgical neck of the humerus?
axillary nerve
- this produces numbness in a patch on the top part of the arm - “sargeant patch”
When might shoulder US be performed?
- it can be used to assess damage to biceps
- it is good for looking for impingement as active movement of the shoulder can be performed
- it is also used for looking for rotator cuff tears and calcification
When is this appearance typically seen?
- this is commonly seen in shoulder dislocation
- the piece of bone that is sticking out is the acromion
- there is loss of the normal shoulder contour, prominent acromion and reduced range of motion
What is shown in this XR??
What nerve is at risk?
anterior dislocation
- this is the most common form of dislocation and usually results from trauma
- the humeral head is not in the glenoid - it is directly under the coracoid and closer to the ribs
- the axillary nerve is at risk in this type of injury
What would a Y-view show in an anterior dislocation?
- the humeral head is positioned anterior to the glenoid (under the coracoid)
Why are posterior dislocations often more difficult to identify?
- it often appears as though the humeral head is sat in the glenoid
How common is posterior dislocation and what causes it?
What sign does it produce on XR?
- it is uncommon and tends to be caused by the 3 Es:
- electricity
- ethanol
- epilepsy
- there is medial rotation of the humeral head so it loses its normal asymmetrical contour
- this produces a characteristic “lightbulb” sign in which the humeral head appears round and the asymmetry is lost
- the Y view is used to distinguish anterior and posterior dislocations
How is angulation described?
How could this fracture be described?
- this is a spiral fracture in the midshaft of the left humerus with moderate medial angulation of the distal segment
- when describing angulation, you need to specify whether you are referring to the proximal or distal segment
- usually the distal segment is described as the proximal segment is fixed relative to the body
What nerve is at risk in a humeral shaft fracture?
radial nerve
- the radial nerve runs around the back of the humerus in the spiral groove so is at risk in humeral shaft fractures
- the deep profunda brachii artery is also at risk
What 3 bones make up the elbow joint?
What are the standard elbow views?
- humerus
- radius
- ulna
- the standard elbow views are AP and lateral
What is the olecranon and capitellum?
What movements are these structures important for?
- the olecranon is on the ulna
- when moving the arm, the olecranon enters the olecranon fossa of the humerus
- the capitellum of the humerus articulates with the radial head and allows for pronation and supination
What 2 lines are important to identify on a lateral elbow view?
- anterior humeral line
- radiocapitellar line
- these 2 lines should intersect each other
What is shown in this image?
How can you tell?
fracture of the radial neck
- there is no displacement as the radial neck is held in place by the annular ligament
- the dark area behind the elbow is a posterior fat pad
- a posterior fat pad is always pathological - there will be a fracture present even if it cannot be seen
Why do fat pads appear in fractures?
Are they always abnormal?
- if you suspect a fracture but there is no obvious bony abnormality, look for fat pads
- effusion / bleeding into the joint lifts the fat pad away from the humeral surface allowing it to be seen on XR as a dark grey shadow adjacent to the bone
- a small anterior fat pad can be normal, but a raised/large one is often pathological (“sail sign”)
- a visible posterior fat pad is always abnormal
What is this deformity?
What is it associated with?
“dinner fork deformity”
- this is associated with a Colles fracture
- the appearance of the wrist is so typical of the underlying fracture that it is considered an “end of bed diagnosis”
What is a Colles fracture?
Why are they difficult to fix and what are they associated with in the future?
- a complete fracture of the radius close to the wrist resulting in upward (posterior) displacement of the radius and obvious deformity
- this is an intra-articular fracture, so the patient will develop arthritis in the future
- these fractures are difficult to fix as they are often comminuted (many small parts)
What fracture type is this appearance associated with?
Smiths fracture (reverse Colles)
How does a Smiths fracture appear on XR?
- the capitate, lunate and distal radius should all sit inside each other in a line on a lateral view
- they are said to be “cupping” each other
- in a Smiths fracture, this alignment is lost
- there is volar displacement and angulation of the fracture fragments
Why are so many views taken in suspected scaphoid fracture?
- they are very difficult to spot
- it is important they are identified as it can lead to avascular necrosis of the proximal part of the bone if left untreated
