Published online by Cambridge University Press: 05 July 2015
‘This is an AP/lateral/oblique radiograph of the right/left wrist, or scaphoid series.’
• AP and lateral.
• Distal radius and ulna.
• Carpal bones: scaphoid, lunate, triquetral, pisiform, trapezium, trapezoid, capitate, hamate.
• If the lunate is anteriorly displaced this is termed a lunate dislocation.
• If the lunate (which is moon-shaped – with the concave side holding the rest of the carpus) – or cup of the lunate are empty then this is termed a perilunate dislocation – the capitate is displaced dorsally.
• Space > 2 mm between scaphoid and lunate is abnormal (scapholunate dissociation) (Terry Thomas sign).
• Normal radius has palmar/volar tilt (2–20°). If lost, suspect a fracture of the radius.
• Radial wrist normally more distal than ulna. If lost, this may suggest that the radius has impacted and is shortened.
• Dorsal angulation fracture of radius = Colles’ fracture.
• Volar angulation fracture of radius = Smith's fracture.
• If there is an intra-articular fracture involving either the posterior cortex or more commonly the anterior cortex of the radius, the vertical fracture pattern causes subluxation of the carpal bones= Barton's fracture (unstable).
• Fractures involving the growth plate. Salter–Harris classification:
I S – Straight through
II A – Above/metaphyseal
III L – Lower/epiphyseal
IV T – Through both metaphyisis and epiphysis
V S – Squashed
• Colles’ and Smith's fractures: distal radial fracture with no joint involved.
• Barton-type fracture: distal radial fracture that is longitudinal and involves the joint space; it can have a volar or dorsal angulation and is associated with carpal displacement (unlike Colles’ or Smith's).
• Tenderness in anatomical snuffbox: ask for four-view scaphoid series.
• Normal radiographs but clinical suspicion: treat as fracture and repeat radiographs in 10–14 days.
• 80% waist: most common fracture (avascular necrosis likely).
• 10% proximal pole (avascular necrosis very likely).
• 10% distal pole (avascular necrosis unlikely).
• Scaphoid fractures may be associated with perilunate dislocation.