Wrist radiographs are ubiquitous on any night of the week in emergency departments, especially when pavements are icy!
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Systematic review
Choosing a search strategy and utilizing it consistently is a helpful method to overcome common errors seen in diagnostic radiology. The order in which you interpret the radiograph is personal preference. A recommended systematic checklist for reviewing musculoskeletal exams is soft tissue areas, cortical margins, trabecular patterns, bony alignment, joint congruency, and review areas. Review the entire radiograph, regardless of perceived difficulty. Upon identifying an abnormality, do not cease the review, put it to the side and ensure to complete the checklist.
Soft tissue
Assess all soft tissue structure for any associated or incidental soft tissue signs
Bone cortex
Check each bone in turn:
pay particular attention to the distal radius, proximal carpal row (especially the scaphoid) and the bases of the metacarpals
Bony alignment
Distal radial contour
Check the contour of the distal radius:
-
AP
the distal radial articular surface should cup the carpals
the articular surface should get progressively more distal towards the radial styloid
radial inclination angle should be 15-25°
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lateral
the radial surface should be smooth
there should be a palmar tilt to the articular surface
volar tilt should be around 10-25°
if these features aren't present, think distal radial fracture
Carpal arcs
Check the carpal arcs:
the articular surfaces of the proximal and distal carpal rows should form three smooth arcs
trace these arcs on the AP film
the spacing between all carpal bones should be 1-2 mm
if the arc is broken or there is a widening of a joint space, think carpal dislocation
Carpal alignment (lateral)
Check lateral alignment:
the distal radius, lunate and capitate should be in a straight line
-
if the line has been disrupted, think:
lunate dislocation: lunate is completely dislocated
perilunate dislocation: capitate and other carpal bones (except lunate) are dislocated
the scapholunate angle should be between 30o and 60o in the neutral position
capitolunate angle should be less than 30o in the neutral position
Joint congruency
Carpometacarpal articulation
Check carpometacarpal joint space:
a 1-2 mm joint space should be seen between the carpals and metacarpals
if the joint space is narrowed, think carpometacarpal dislocation
One of the commonest misses in trauma films of the hand and wrist is a dislocation of the 5th carpometacarpal joint which may cause significant morbidity if the diagnosis is delayed.
Common pathology
Colles fracture
the most common distal radial fracture in any adult group
peak incidence in elderly women
usually, following a fall onto an outstretched hand
dorsal angulation of the distal fracture component
important to determine if there is intra-articular extension
more: Colles fracture
Smith fracture
account for less than 3% of forearm fractures
more common in young males and elderly females
fall onto flexed wrist or direct blowback of wrist
classically, an extra-articular distal radius fracture with palmar angulation of distal fracture fragment
also called the reverse Colles
more: Smith fracture
Scaphoid fracture
80% of all carpal bone fractures
usually young adults
fall on an outstretched hand
80% of fractures are through the waist of the scaphoid
if suspected, perform additional scaphoid views
may be radiographically occult - should be followed up if pain persists
more: scaphoid fracture
Triquetral fracture
second most common carpal bone fracture
hyperextension or avulsive injury
frequently seen as dorsal chip fractures on lateral views only
more: triquetral fracture
Perilunate dislocation
typically occur in young adults
following a fall on the dorsiflexed wrist
best detected on lateral view - the lunate articulates with distal radius but capitate does not sit in lunate ‘cup’
60% associated with scaphoid fracture
more: perilunate dislocation
Don't miss...
Scapholunate dissociation
injury to the scapholunate and radiolunate ligament results in scapholunate dissociation and significant instability
the scapholunate space is widened (> 4 mm) - the Terry Thomas sign
Lunate dislocation
much less common than perilunate dislocation
commonly occur in young adults
fall onto a dorsiflexed wrist
more: lunate dislocation
Carpometacarpal dislocation
rare but important injury to dominant hands of younger males
younger male predominance
often occur after a punch followed by a fall
reduction of joint space on the AP
best seen on an oblique study
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