Upper Limb Trauma X-rays

Question 1

History features that suggest that an X-ray should be done?

Answer 1

Mechanism of injury:
• High velocity injuries are more likely to cause a fracture than low velocity
• Impaction/rotation/distraction

Site of bone tenderness/presence of deformity

Patient age

Question 2

Why is one X-ray view rarely enough to find fractures?

Answer 2

Fractures may be invisible

Alignment cannot be fully assessed

Two views are often enough to assess the region

Question 3

Special circumstances in which more than 2 X-ray views are used?

Answer 3

Cervical spine:
• AP view
• Lateral view
• To view the odontoid peg, the patient must open their mouth

Scaphoid requires 4 views, as it is prone to complications:
• AP
• Lateral
• 2 oblique views

Question 4

Different types of fracture appearances?

Answer 4

• Lucency crossing bone
• Cortical extension/hypertrophy
• Spiral/transverse fractures - occur when a rotating force is applied to the bone
• Comminuted fracture - bone breaks into more than 2 fragments, usually following high-impact trauma
• Joint involvement
• Angulation - fragments of bone are at angles to each other; usually encountered after a punch injury
• Displacement - 2 ends of the bone fragments are not lined up straight
• Impaction - bone fragments are driven into one another
• Avulsion - separation of a small fragment of bone cortex at the site of attachment of a ligament/tendon

Question 5

What bony entities on X-ray mimic acute avulsion fractures?

Answer 5

All of these have a COMPLETELY CORTICATED CONTOUR:
• Sesamoid bones (embedded within tendon/muscle)
• Accessory ossification centres
• Old, non-united fractures

Question 6

Areas to assess bony alignment in the upper limb?

Answer 6

Acromioclavicular joint

Glenohumeral joint

Elbow:
• Radio-capitellar (drawing a line down the middle of the radius should meet the capitulum)
• Humero-capitellar (drawing a line down the middle of the capitulum should bisect the capitulum)

Lateral wrist

Question 7

Soft tissue abnormalities and normal features seen around the distal humerus on X-ray?

Answer 7

Fat density may be seen anterior to the distal humerus on normal X-rays

If an elbow effusion is present (trauma is a common cause), a displaced fat pad becomes visible posterior to the distal humerus (POSTERIOR FAT PAD SIGN)

Question 8

Describe a visible posterior fat pad

Answer 8

Always ABNORMAL; it is a sensitive indicator of elbow trauma

Question 9

Which fractures do child bones suffer and why?

Answer 9

Child bones are soft and so they bend/bow, rather than snapping and splintering; so they sustain:
• Buckle fracture (compression fracture on one side of a bone that causes the bone to bend or buckle toward the damaged side)
• Plastic bowing
• Greenstick fracture (incomplete fracture - one side of the bone is fractured and the other only bent)

Question 10

Describe avulsion fractures in children

Answer 10

In children, it is common for ligaments/tendons to avulse their soft, bony attachments, e.g: the medial epicondyle of the humerus can be displaced by traction from the attached flexor tendons

Question 11

Appearance of the physis?

Answer 11

AKA growth plate; seen as a lucency between the epiphysis and metaphysis that may stimulate a fracture

Question 12

Injury of the physis?

Answer 12

Weakest part of a developing bone and so it is prone to injury, which can be complicated by growth deformity

Physes can look similar to fractures

Question 13

Grading of growth plate fractures?

Answer 13

Salter-Harris classification is used, with 9 types

Question 14

Describe non-accidental injury (NAI)

Answer 14

Femoral fractures of different ages indicate more than one injury

If a carer’s history does not fit the injury, suspect NAI

Question 15

Bony ring fractures?

Answer 15

Rings are inherently strong structures; bones and joints often form rings to help share the transmission of force and increase strength, e.g: spinal canal, pelvis and forearm and lower leg

It is difficult to disrupt (fracture/dislocate) a ring in only one place, esp. where bone displacement is present; in other words, if a bony ring is injured, two or more disruptions WILL be seen

Question 16

Appearance of foreign material on X-ray?

Answer 16

To be seen on an X-ray, foreign material must be different in density to surrounding tissues

In general, metal and glass can be seen but plastic and wood are often invisible

Question 17

Pathological fractures?

Answer 17

Suspect when the bone abnormality seems out of proportion to the mechanism of injury, e.g: normal stresses on a weakened skeleton

Question 18

Causes of a weakened skeleton?

Answer 18

Can be:
• Focal, e.g: a metastatic deposit causing a clavicle fracture
• Diffuse, e.g: due to osteoporosis or other metabolic bone disease

Question 19

What is a Colles fracture?

Answer 19

Tends to occur in elderly patient with osteoporosis

Fracture of the distal radius in with dorsal (posterior) and radial displacement of the wrist and hand

Question 20

How many carpal bones do children have?

Answer 20

8, as do adults, but only 4 are ossified and so only 4 can be seen on X-ray

Question 21

What are scaphoid fractures?

Answer 21

Tend to be seen with young males; pain is felt in the anatomical snuffbox

Commonly occur at the mid-scaphoid

Prone to complications, like AVN

Question 22

What are surgical neck of the humerus fractures?

Answer 22

Tend to occur in post-menopausal fractures and are often comminuted and can damage axillary nerve

Sclerosis indicates impaction

Question 23

Upper limb injuries that are easily missed?

Answer 23

Posterior shoulder dislocation - if the humerus dislocates posteriorly, the lack of displacement makes it difficult to appreciate on an AP X-ray

Supracondylar fracture

Scaphoid fracture

Bennett’s fracture

Question 24

How to see posterior shoulder dislocations?

Answer 24

An oblique view should be obtained, showing that the humeral head lies posterior to the articular surface of the glenoid

Question 25

How to see supracondylar fractures?

Answer 25

Must assess humerocapitellar alignment; visible posterior fat pad also helps

Question 26

Complications of supracondylar fractures?

Answer 26

Can damage the brachial artery acutely

If untreated, these will malunite, causing lifelong disability

Question 27

How to see scaphoid fractures?

Answer 27

Take a repeat X-ray after 10 days

OR

Use an MRI scan to confirm/exclude a fracture

Question 28

Complications of scaphoid fractures?

Answer 28

Proximal scaphoid blood supply can be disrupted by a fracture, making it prone to non-union

OR

AVN

Leading to early wrist OA

Question 29

What is a Bennett’s fracture?

Answer 29

Involves the articular surface of the first metacarpal base

Tendons pulling on the thumb distal to the fracture can cause displacement and, if this is missed and not treated, deformity, dysfunction and arthritis will develop