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
Why is the detection of a scaphoid fracture important?
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
Scaphoid fracture percentages?
70-80% waist
20% proximal
10% distal
proximal and waist # associated with avascular necrosis
Avascular necrosis in terms of scaphoid fracture?
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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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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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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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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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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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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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