Fracture interpretation for medical students

transcript

Approach to Fracture Interpretation For Medical Students

Dr Rory O’DonohoeHonorary Lecturer

Department of RadiologySt. Vincent’s University Hospital

Dublin 4Ireland

www.svuhradiology.ie

How do we visualise fractures?

• When a fracture causes separation of bone fragments, more x-ray photons get through the gap and we see a lucent (dark) line

How do we visualise fractures?

• When a fracture causes overlapping of bone fragments, more x-ray photons are blocked and we see an area of increased density (more white)

What radiographic views do we need?

• To properly examine a bone or a joint, we need at least two views

• Usually these views are obtained at right angles to each other (for example, AP and lateral)

• If the fracture is displaced in the same direction as the x-ray beam, it may only visible on an orthogonal view (hence the need for more than one view)

Lateral view of elbow, left shows effusion but no fracture. AP view, right, shows the fracture line.

A little on the description of projections…

• Know what PA and AP mean:

• They refer to the direction of the beam

• In postero-anterior (PA) projections, the beam is fired from behind the patient and the detector is in front of them (and vice-versa for AP)

• If in doubt as to whether it’s PA or AP, just call it a frontal projection- this applies to chest radiographs too

Special cases

• Some fractures are often so hard to see that we need more than two views (a scaphoid series involves four views) – and even with these we frequently still have difficulty diagnosing them

• Some fractures are better identified by their effect on the soft tissues around them, for example fat pad displacement in elbow fractures, as will be explained later…..

Is it definitely a fracture?

• Some normal appearances can be mistaken for fractures

• Growth plates are a frequent source of confusion - if in doubt, check the age of the patient

• Accessory ossicles often persist into adulthood and can usually be identified by their classic locations (entire textbooks are dedicated to cataloguing accessory ossicles)

• If in doubt as to whether it’s a fracture or not, remember you can always correlate with clinical examination. Are they tender there?

How to describe fractures

• Medicine requires clear and reproducible ways to describe things - it’s not just for exams!

• You need to have a clear knowledge of the terms used to describe fractures

• Start with the easy stuff!

• Describe the study (e.g. “These are AP and lateral radiographs of the right humerus.”)

• What is the age and sex of the patient?

• Don’t point at the image. If you see the fracture, describe it…..

• What bone is broken?

• While this seems obvious, it requires that you remember all of your anatomy!

• Many medical students are a little rusty on the carpal bones and tarsal bones

• If you want to quickly revise, check out the anatomy section on our website at

http://www.svuhradiology.ie/diagnostic-imaging/radiological-anatomy/

How to describe fractures• What part of the bone is broken?

• For long bones we assess whether it’s the proximal epiphysis, proximal metaphysis, diaphysis, distal metaphysis, distal metaphysis

• In many of these, certain parts of the bone will have a specific anatomical name (e.g. tibial plateau, radial head, femoral neck), so you need to be familiar with these too

• For shorter bones (e.g. a middle phalanx in a finger), we usually describe the location with the terms proximal, mid and distal rather than metaphysis etc.

• Is the fracture comminuted?

• A comminuted fracture comprises more than two fracture fragments

• This may determine whether the fracture can be treated in cast or will require surgery

• Occasionally it can be difficult to be certain, in which case the orthopaedic team may request a CT to further assess the fracture

• Describe the fracture line

• Transverse, oblique, spiral – the majority of fractures can be described with one of these terms

• Occasionally, fractures will be multidirectional, for example ‘t-shaped’, ‘h-shaped’

Transverse fracture of the tibial diaphysis

• Is there displacement?

• e.g. “there is lateral displacement of the distal fracture component”

• Is there angulation?

• e.g. “there is medial angulation of the distal fracture component”

• As you would expect, the more displaced and/or angulated a fracture is, the more likely it will require surgical intervention

Fracture of the distal radius with severe dorsal displacementand dorsal angulation

How to describe fractures• Is the fracture intra-articular?

• Does the fracture line (or one of them if comminuted) involve an articular surface?

• Intra-articular fractures are associated with a poorer long-term outcome and can result in secondary osteoarthritis

• If a joint is involved, does the joint demonstrate normal alignment?

• If not, is it dislocated (articular surfaces no longer in contact) or subluxed (articular surfaces partly in contact)

• For example, ankle fractures are often associated with subluxation of the joint

Comminuted intra-articular fracture of the proximal aspect of the first metacarpal

Fractures of the fibula and talus with ankle subluxation

• Simple vs. compound fractures are more relevant to clinical examination but should be considered

• Simple fractures involve the bone only whereas compound fractures break the skin surface and are therefore prone to infection

• Often we won’t be able to tell this by looking at radiographs, but occasionally it will be obvious

• Now that you’ve been armed with all this background information, here are 10 cases for you to review

• Practice describing each fracture as you would in an exam

Case 1

• 30 year old with pain in the right ankle after a fall

Case 1 - Image 1

Case 1 - Image 2

Case 1

• AP and lateral radiographs of the right ankle in a skeletally mature patient

• There is an oblique, non-displaced fracture of the distal shaft of the right tibia

Case 2

• 27 year old with pain in the right shoulder after a sports injury

Case 2

• AP radiograph of the right shoulder

• There is a completely displaced comminuted fracture of the right clavicle at the junction of the middle and lateral thirds

Case 2

• The fracture is described as comminuted as there are three separate fracture fragments (arrows)

Case 3

• 35 year old with pain in her toe after a night out

Case 3 - Image 1

Case 3 - Image 2

Case 3

• Frontal and oblique radiographs of the left foot

• There is a minimally displaced transverse fracture of the distal shaft of the left third proximal phalanx

• Note how difficult it is to see the fracture on the frontal projection (it’s just about visible as a transverse dense line)

• This is why we need two views when assessing for fractures

• In this case the projections are frontal and oblique - the projections aren’t necessarily always at right angles to each other

Case 4

• 40 year old with inversion injury of the right ankle

Case 4 - Image 1

Case 4 - Image 2

Case 4

• AP and lateral radiographs of the right ankle

• There is a minimally displaced spiral fracture of the right distal fibula at the level of the syndesmosis

Case 5

• 15 year old with pain in the left shoulder after a fall

Case 5 - Image 1

Case 5 - Image 2

Case 5• Normal radiographs!

• Don’t be fooled by the left proximal humeral growth plate (arrows)

• There appear to be two lines through the left proximal humerus as the growth plate runs obliquely through the plane of the radiograph

• Note there are also growth plates visible at the acromion and coracoid processes

• Remember in young patients to consider if what you’re looking at might be a growth plate

Case 6

• 87 year old with pain in the hip after a fall out of bed

Case 6

• AP radiograph of the pelvis in an 86 year old female

• There is a linear non-displaced fracture of the right femoral neck

Case 7

• 34 year old with pain in the anatomical snuffbox

Case 7 - Image 1

Case 7 - Image 2

Case 7 - Image 3

Case 7 - Image 4

Case 7• Scaphoid fractures can be notoriously

difficult to see. Four views are obtained when a scaphoid fracture is suspected.

• A comminuted fracture of the waist of the left scaphoid is visible on this scaphoid series - this example is easier to spot than most scaphoid fractures

• If a scaphoid fracture is still suspected despite not being visible on radiographs, the wrist should be immobilised and repeat radiographs performed in 7-10 days at which time the fracture may be more apparent.

Case 8

• 40 year old with pain in the right elbow after a fall

Case 8 - Image 1

Case 8 - Image 2

Case 8

• Not all fractures are visible on radiographs, particularly in the acute setting

• There may however be signs of the fracture in the surrounding soft tissues

• The classic example is in the elbow where an elbow joint effusion causes elevation of the anterior and posterior fat pads

Case 8

• Remember, fat allows the transmission of a relatively large number of x-ray photons and therefore appears dark

• Note the two triangles of fat anterior and posterior to the distal humerus

• These are the fat pads that have been displaced by fluid in the elbow joint

• In practice, this is presumed to be due to a radial head fracture although the fracture line is not visible

Case 9

• Pain in the right ankle after jumping from a height

Case 9 - Image 1

Case 9 - Image 2

Case 9• No fracture!

• There is a boney density adjacent the lateral cuneiform

• This is an accessory ossicle

• Note how rounded it appears, and it doesn’t have the sharp edges of the fractures in the previous cases

• Details of the common locations of accessory ossicles can be found in textbooks (and on google)

Case 10

• Pain in the right hand after a fall

Case 10 - Image 1

Case 10

• Fracture of the distal radius

• Always remember to look at the edge of the film!

Summary

• It’s important to have a systematic approach to describing fractures, incorporating all the essential features such as displacement, comminution and intra-articular extension

• We hope that this tutorial has made you more confident in your approach to radiographs of fractures

Fracture interpretation for medical students

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