Scapholunate ligament injury
The scapholunate ligament is a key stabiliser of the proximal carpal row.
Presentation
- dorsal-radial wrist pain
- pain with loading or extension
- clicking or sense of instability
Examination
The scaphoid shift test may reproduce pain or a clunk, but comparison with the opposite side is important because laxity varies.
Imaging
Look for:
- widened scapholunate interval
- scaphoid flexion/ring sign
- DISI alignment on lateral view
Stress radiographs, MRI and wrist arthroscopy are used selectively. Arthroscopy remains the best method for directly assessing ligament integrity and cartilage.
Chronic consequence
Untreated static instability can progress to scapholunate advanced collapse (SLAC) arthritis.
The scapholunate ligament is a major stabiliser between scaphoid and lunate. Complete disruption can allow the scaphoid to flex and the lunate to extend, producing a DISI pattern.
Clinical features may include:
- dorsal wrist pain
- weakness
- clicking
- tenderness over scapholunate interval
Dynamic instability may be absent on resting radiographs.
Perilunate injury
Perilunate dislocations and fracture-dislocations are high-energy injuries that are often missed.
Assess:
- median nerve function
- carpal alignment on true lateral radiograph
- associated scaphoid or other carpal fractures
A dislocated carpus requires urgent reduction. Definitive treatment usually includes repair or fixation of disrupted carpal structures.
Radiographic principle
On a normal lateral radiograph, radius, lunate, capitate and third metacarpal should be approximately collinear. Loss of this relationship is a major clue to perilunate or lunate dislocation.
Imaging
Look for:
- widened scapholunate interval
- altered scapholunate angle
- ring sign of flexed scaphoid
- DISI on lateral view
Stress views and advanced imaging may help, but arthroscopy can provide direct assessment in selected cases.
Chronic progression
Untreated instability can produce scapholunate advanced collapse (SLAC), with predictable degenerative changes.
Once established arthritis exists, ligament reconstruction alone may no longer be appropriate.
Perilunate injuries
Perilunate dislocation and fracture-dislocation are high-energy injuries and are frequently missed.
On the lateral radiograph, alignment of:
- radius
- lunate
- capitate
must be checked. In lunate dislocation, the lunate itself is displaced.
Associated scaphoid fracture produces a trans-scaphoid perilunate fracture-dislocation.
Acute management
These injuries require:
- urgent reduction
- neurovascular assessment
- attention to median nerve compression
- CT for fracture detail where appropriate
- definitive restoration of carpal alignment and ligament/bone stability
Definitive treatment commonly involves open or arthroscopic-assisted repair/fixation depending on pattern and expertise.
Median nerve
Acute carpal-tunnel symptoms can occur due to displaced carpal structures and swelling. Progressive median nerve compromise may require decompression.
FRCS synthesis
For carpal instability, think in terms of carpal alignment over time. Acute ligament disruption may be reconstructible; chronic collapse with arthritis requires a different salvage strategy.