X-rays and the Upper Limbs

Question 1

Why is one x-ray view sometimes not enough to visualise a fracture?

Answer 1

Fractures may be invisible, alignment cant be fully assessed

Question 2

What is normally the best number of x-ray views to be taken?

Answer 2

Two views

Question 3

What are some examples of when more than two x-ray views are needed?

Answer 3

Cervical spine = AP, lateral and odontoid peg needed

Scaphoid = AP, lateral and two obliques needed

Question 4

What are some ways fractures can appear on x-rays?

Answer 4

Lucency crossing bones, cortical expansion, spiral/transverse, comminution, joint involvement, angulation, displacement, impaction, avulsion

Question 5

What are some bony entities which superficially resemble acute avulsion fractures?

Answer 5

Sesamoid bones, accessory ossification centres and old non-united fractures

Question 6

How can you tell acute avulsion fractures apart from their mimics?

Answer 6

Avulsion fracture fragments are incompletely corticated = all mimics have a completely corticated contour

Question 7

What are some joints that can be used to assess bony alignment?

Answer 7

Acromioclavicular, glenohumeral , elbow (radio-capitellar and humero-capitellar), lateral wrist

Question 8

Where may fat density be seen on a normal x-ray?

Answer 8

Anterior to the distal humerus

Question 9

What is the posterior fat pad sign?

Answer 9

Visible posterior fat pad = indicates elbow trauma which has caused an effusion

Question 10

How are children’s bones different form adult bones?

Answer 10

They are soft so “bend and bow” rather than £snap and splinter” = buckle fracture, plastic bowing
Fractures are often incomplete = greenstick fracture

Question 11

What is it common for ligaments and tendons in children to do?

Answer 11

Avulse their soft bony attachments

Question 12

How may a physis appear on an x-ray?

Answer 12

Lucency between the epiphysis and metaphysis = may look like a fracture

Question 13

Why is the physis prone to injury?

Answer 13

It is the weakest part of developing bone

Question 14

Where is the epiphysis always seen on normal x-rays?

Answer 14

Always centred on the metaphysis

Question 15

What kind of fractures are Salter-Harris fractures?

Answer 15

Growth plate (physis) fractures

Question 16

What may be an indication of a non-accidental injury (NAI)?

Answer 16

An injury that doesn’t fit with the carers description of the history

Question 17

Why do bones and joints form rings?

Answer 17

To help share the transmission of force and increase strength (e.g spinal canal, pelvis)

Question 18

Why should you expect at least two disruptions when a bony ring is injured?

Answer 18

Its difficult to disrupt a ring in only one place (some disruptions may be fractures and others dislocations)

Question 19

What foreign objects may be seen on an x-ray?

Answer 19

Dense objects = metal and glass

Plastic and wood are often invisible

Question 20

When should you suspect a pathological fracture?

Answer 20

When the bone abnormality seems out of proportion to the mechanism of injury

Question 21

What are pathological fractures typically a result of?

Answer 21

Normal stresses on a weakened skeleton

Question 22

What are some examples of pathological fractures?

Answer 22

Colles fracture, radial buckle fracture, scaphoid fracture and surgical neck of humerus fracture

Question 23

What are some features of a Colles fracture?

Answer 23

Occur in elderly with osteoporosis, dorsal angulation of the radius, associated with ulnar styloid fracture

Question 24

What are some features of a radial buckle fracture?

Answer 24

Occurs in children with soft bones, only half of them are visible

Question 25

What are some features of a scaphoid fracture?

Answer 25

Occurs in relatively young men, pain in anatomical snuffbox, commonly occurs mid-scaphoid

Question 26

What are some features of a surgical neck of humerus fracture?

Answer 26

Occurs in post menopausal females, sclerosis indicates impaction, often comminuted, can damage axillary nerve

Question 27

What are some commonly missed upper limb injuries?

Answer 27

Posterior shoulder dislocation, supracondylar fracture, scaphoid fracture, Bennet’s fracture

Question 28

How should a posterior shoulder dislocation be imaged?

Answer 28

Oblique view should always be obtained = shows humeral head lies posterior to the articular surface of the glenoid

Question 29

Why are AP views not suitable for imaging a posterior shoulder dislocation?

Answer 29

Lack of displacement makes it difficult to appreciate

Question 30

What are some features of a supracondylar fracture?

Answer 30

Found be assessing the humero-capitellar alignment
Has visible posterior fat pad
Can damage brachial artery acutely and will malunite if untreated

Question 31

How should a scaphoid fracture be imaged?

Answer 31

Can be invisible despite multiple views

Repeat the x-ray after 10 days and MRI can be useful in confirming/excluding a fracture

Question 32

What may a scaphoid fracture cause?

Answer 32

Proximal scaphoid blood supply can be disrupted, making it prone to non-union and avascular necrosis = may cause early wrist osteoarthritis

Question 33

What is involved in a Bennett’s fracture?

Answer 33

Articular surface of wrist of first metacarpal base

Question 34

What may a Bennett’s fracture lead to?

Answer 34

Tendons pulling on the thumb distal to the fracture causes displacement = can lead to deformity, dysfunction and osteoarthritis