Wrist radiographs obtained after trauma should evaluate for fracture, dislocation and signs of ligamentous injury.
The following are helpful to assess for traumatic misalignment on frontal view:
- Three carpal arcs of gilula
1. Outlines proximal convexities of scaphoid, lunate, and triquetrum
2. Outlines distal concave surface of the same bones.
3. Outlines proximal curvatures of capitate and hamate.
Disruption of arc may indicate ligamentous injury or fracture at site of broken arc.
Normal Radiographic Criteria of the Wrist
Measure scapholunate interval. Widening (>3mm) suggests scapholunate ligament injury and/or scapholunate dissociation.
Abnormal carpal morphology may indicate dislocation. A common example of this is triangular appearance of lunate “piece of pie sign” suggesting lunate or perilunate dislocation which is more readily apparent on lateral view.
Positive or negative ulnar variance occurs when the level of the ulna is >2.5mm distal or proximal to radius at the distal radio-ulnar joint. This can be congenital, seen in the setting of distal radius/ulnar fractures, or distal radial ulnar joint ligament injuries.
The following are helpful to assess for traumatic misalignment on lateral view:
Assess for technical adequacy by making sure lateral view is well positioned with pisiform projecting between the distal pole of scaphoid and head of capitate.
- Identify lunate or perilunate dislocations
Lunate dislocation results in disruption of radiolunate articulation with abnormal volar displacement and rotation.
- Perilunate dislocation involves dorsal dislocation of capitate relative to lunate with normal alignment of radiolunate articulation.
- Assess angulation of the lunate on lateral view relative to other carpal bones.
- Scapholunate angle is the angle between long axis of the scaphoid and mid axis of the lunate. (Normal 30-60 degrees)
- Capitolunate angle is the angle between the long axis of capitate and the mid axis of the lunate. (Normal <30 degrees)
- A scapholunate angle <30 degrees and capitolunate angle >30 degrees suggests volar intercalated segment instability (VISI)
- A scapholunate angle >60 degrees and capitolunate angle >30 degrees suggests dorsal intercalated segment instability (DISI)
- A scaphoid view is obtained when there is clinical concern for scaphoid fracture (anatomical snuffbox tenderness).
- PA view obtained with ulnar deviation of the wrist.
- Follow up radiographs should evaluate for healing and the development of avascular necrosis.
FINDINGS: Mildly displaced fracture of the scaphoid waist with interval resorption of fracture plane and increased sclerosis of proximal fragment, concerning for osteonecrosis.
On each view, trace the cortices of radius, ulna, carpals, and metacarpals. Look carefully for cortical disruptions, linear lucencies and small osseous fragments. Look very closely at the scaphoid.
Example report negative for traumatic injury
FINDINGS:
- No acute fracture. Normal carpal bone alignment.
IMPRESSION:
- No acute fracture or traumatic malalignment.
If anatomic snuffbox tenderness is present, recommend immobilization and repeat radiographs in 7-10 days.