OrthoNet

SLAC
Scapho-Lunate Advanced Collapse - SLAC Wrist

- primary injury is a disruption of the scapholunate ligament
- this results in rotary subluxation of the scaphoid - it flexes in a palmar direction
- when flexed palmarly, there is incongruous joint contact between the proximal scaphoid and distal radius, with significantly increased contact pressures.
- abnormal forces are transmitted from the scaphoid to distal radius, and from the capitate to lunate
- as the scaphoid shortens, the capitate experiences increased load and begins to fall into the gap between the scaphoid and lunate.

Stages

Stage I: radial styloid and distal-radial aspect of scaphoid degeneration

Stage IIA: entire radioscaphoid articulation involved
Stage IIB: radioscaphoid and STT joint arthritis

Stage III: radioscaphoid, scaphocapitate, and lunocapitate articulations involved

Surgical Treatment - SLAC Wrist

Stage I: radial styloid
- radial styloid excision to remove impingement on the radial side of the wrist - may be done alone or combined with distal scaphoid fusion: STT or scapho-capitate
- scaphoid-trapezium-trapezoid fusion (STT)
- scaphoid-capitate fusion

Stage II: radioscaphoid +/- scaphotrapezial/trapezoidal
- scaphoid excision plus limited intercarpal fusion (�four-corner� capitate-lunate-hamate-triquetrum fusion, or lunocapitate fusion)
- proximal row carpectomy - some evidence that PRC may preserve more motion than intercarpal fusion

Stage III: radioscaphoid, scaphocapitate, lunocapitate
- scaphoid excision and four-corner fusion
- scaphoid excision and lunocapitate fusion
- wrist arthrodesis

From a technical point of view, in all intercarpal fusions:
- thoroughly excise the cartilage and subchondral bone
- preserve carpal height
- bone graft generously
- correct capitate-lunate alignment; in particular, if a DISI pattern has developed, it is important to get the lunate out of its extended position to restore wrist extension and reduce radiocapitate impingement