Wrist- Images to Description Flashcards

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The scaphoid fat pad or stripe sign is defined as obliteration or lateral displacement of the normal scaphoid fat pad.

A positive sign usually indicates a scaphoid fracture, although it may also be associated with a radial styloid or proximal first metacarpal fracture.

Is it best visualised on poster-anterior and oblique views of the wrist.

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The pronator quadratus sign can be an indirect sign of distal forearm trauma.

It relies on displacement of the fat pad that lies superficial to the pronator quadratus muscle.

On lateral wrist radiographs, the pronator fat pad normally appears as a thin radiolucent triangle, with its base attached to the palmar surface of the distal radius. It is observed ~90% of the time

Displacement, anterior bowing, or obliteration of the fat plane in the setting of trauma may indicate a distal radius or ulna fracture. Various studies have described a wide ranging sensitivity for fracture ranging from 26 to 98%; thus a negative pronator quadratus sign does not exclude fracture.

In the absence of trauma, there are other causes for a positive pronator quadratus sign:

muscle strain or haematoma

inflammatory conditions

infectious conditions, e.g. osteomyelitis or cellulitis

septic arthritis of the wrist

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Triquetral fractures are carpal bone fractures generally occuring on the dorsal surface of the triquetrum.

The triquetral may be fractured by means of impingement from the ulnar styloid, shear forces, or avulsion from strong ligamentous attachments.

They are the second commonest carpal bone fracture, after the scaphoid.

The usual injury mechanism is falling onto an outstretched hand in ulnar deviation.

Less commonly, it may be caused by a direct blow to the dorsum of the hand, a situation where commonly other carpal fractures are seen.

On plain film, dorsal avulsion injuries are best detected on a lateral projection, where typically an avulsed flake of bone is identified lying posteriorly to the triquetral bone (see pooping duck sign).

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Hamate fracture

Rare

Often in association with other injuries

  • Dislocation of 4th/5th MCs
  • Triquetral fractures

Further imaging often required to demonstrate

They occur from the hamate fracturing after blunt trauma, falls, and in sports player (e.g. golf, baseball, racquet sports) from a direct blow while swinging.

Stress fractures have also been reported.

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Fracture of the trapezium

Isolated fractures of the trapezium are only thought to account for 3 - 5% of all carpalfractures

They often occur as a result of a high energy trauma

Direct/indirect axial loading

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7
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Why is the detection of a scaphoid fracture important?

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Most common carpal fracture (80%)

Male>female

20-30yrs

Fracture is not always visible on plain films

Risk of complications if fracture missed and plain film will miss 15-20%

COMMON CAUSE OF LITIGATION

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8
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Scaphoid fracture percentages?

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–70-80% waist

–20% proximal

–10% distal

–proximal and waist # associated with avascular necrosis

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9
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Avascular necrosis in terms of scaphoid fracture?

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–Occurs in 15-30% of scaphoid fractures

–Almost always involves proximal pole

–More proximal the fracture line = greater the risk of avascular necrosis

–Radiology: collapse, fragmentation and sclerosis.

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10
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Scapholunate dislocation

–Intercarpal joints

–3mm or > indicates ligamentous rupture

‘ Terry Thomas sign’

  • Usually relates to complete disruption of the scapholunateinterosseous ligament (SLIL)
  • Often associated with additional injuries
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11
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Lunate dislocation

Involves all intercarpal joints and disruption of most of the major carpal ligaments

Anterior dislocation and forward rotation of lunate

Lunate appears triangular on DP projection

Often has poor functional outcome

Most severe of carpal instabilities

Most commonly associated with a trans-scaphoid fracture

Involves all the intercarpal joints and disruption of most of the major carpal ligaments

Produces volar dislocation and forward rotation of lunate

Concave distal surface of lunate comes to face anteriorly

Capitate drops into space vacated by lunate

Capitate and all other carpal bones lie posterior to lunate on lateral radiograph

Triangular appearance of lunate on frontal projection

Risk of Median Nerve damage

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12
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Perilunate Dislocation

High energy hyperextensioninjury

Capitate and other carpal bones are displaced dorsal to lunate

Lunate remains located in the fossa of the distal radius

61% associated with scaphoid fractures

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13
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Trans-scaphoid Perilunate Dislocation

Overall, carpal dislocations account for less than 10% of all wrist injuries.

Perilunate dislocations typically occur in young adults with high energy trauma resulting in loading of a hyperextended, ulnarly deviated hand.

Around 60% of perilunate dislocations are associated with a scaphoid fracture which is then termed a trans-scaphoid perilunate dislocation.

In a trans-scaphoid perilunate dislocation the proximal scaphoid maintains its lunate relationship, and the distal scaphoid and remainder of the carpal bones displace dorsally

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14
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Kienböck’s Disease

–Avascular necrosis of the lunate

–Dominant wrist, men aged 20-40 years

–May follow some form of trauma

–Blood flow to lunate is disrupted

–Bone substance becomes soft, granular and fragmented

–Lunate becomes squashed and flattened = OA

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15
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Smiths Fracture

Smith fractures, also known as Goyrand fractures in the French literature, are fractures of the distal radius with associated volar angulation of the distal fracture fragment(s).

Classically, these fractures are extra-articular transverse fractures and can be thought of as a reverse Colles fracture.

The term is sometimes used to describe intra-articular fractures with volar displacement (reverse Barton fracture) or juxta-articular fractures.

Smith fractures account for less than 3% of all fractures of the radius and ulna and have a bimodal distribution: young males (most common) and elderly females

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16
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Barton’s Fracture -Dislocation

Barton fractures are fractures of the distal radius. It is also sometimes termed the dorsal type Barton fracture to distinguish it from the volar type or reverse Barton fracture.

Barton fractures extend through the dorsal aspect to the articular surface but not to the volar aspect.

Therefore, it is similar to a Colles fracture.

There is usually associated dorsal subluxation/dislocation of the radiocarpal joint.

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Reverse Barton’s Fracture

Reverse Barton fractures, also known as volar type Barton fractures, represents an intra-articular distal radial fracture with volar displacement.

In fact, the reverse Barton fracture is a type II Smith fracture: oblique distal intra-articular radial fracture.

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Radial Styloid Fracture/ –Chauffers fracture

–Intra-articular fracture

–Directtrauma typically a blow to the back of the wrist or,

–Forceddorsiflexion and abduction

Associated injuries include:

–Scapholunatedissociation

–Trans scaphoid perilunatedislocation

–Ulnar styloid fracture

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Dislocation of DRUJ

Isolated distal radioulnar joint (DRUJ) dislocations are rare and are more commonly part of complex forearm fracture-dislocations.

Wrist pain, swelling and deformity following FOOSH or direct trauma. The patient will be unable to supinate/pronate the forearm

This injury is typically described by the position of the ulna compared to the radius

True lateral radiograph of the wrist is vital (as little as 10º of rotation can result in misinterpretation)

Widened distal radioulnar joint space on frontal projections, with dislocation/subluxation evident on lateral projections

20
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Discuss wrist fractures in children

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–Forearm fractures account for 40% to 50% of all childhood fractures.

–Aboutthree out of four forearm fractures in children involve the wrist-end of the radius.

–Bucklefractures of distal radius common, often subtle.

–Scaphoid fracture v rare before puberty.

–Epiphyseal injury may show as misalignment.

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Buckle Fracture
Torus fractures, also known as buckle fractures, are incomplete fractures of the shaft of a long bone that is characterised by bulging of the cortex.

They result from trabecular compression from an axial loading force along the long axis of the bone.

They are usually seen in children, frequently involving the distal radial metaphysis.

These type of fractures are more common in children, especially aged 5-10 years, due to the elasticity of their bones.

Plain radiograph

Distinct fracture lines are not seen

Subtle deformity or buckle of the cortex may be evident

In some cases, angulation is the only diagnostic clue

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Greenstick fracture

Greenstick fractures are incomplete fractures of long bones and are usually seen in young children, more commonly less than 10 years of age.

They are commonly mid-diaphyseal, affecting the forearm and lower leg. They are distinct from torus fractures.

Can occur following an angulated longitudinal force applied down the bone (e.g. an indirect trauma following a fall on an outstretched arm), or after a force applied perpendicular to the bone (e.g. a direct blow).

This fracture is very different, and much less common, than the torus fracture that results in buckling of the cortex on the concave side of the bend and an intact convex surface.

Plain radiograph

Usually mid-diaphyseal

Occur in tandem with angulation

Incomplete fracture, with cortical breech of only one side of the bone