Scapho-lunate Advanced Collapse (SLAC)

Definition

Advanced arthritis of the radiocarpal and midcarpal joints due to progressive instability/dissociation between the scaphoid and lunate (carpal) bones.

Symptoms

Dorsal (top side) wrist joint pain localized over the region of the scapholunate interval.
Progressive wrist stiffness and weakness.
Increased pain with weight bearing across the wrist (push-up activity).

Pathology

Chronic ligament instability between the scaphoid and lunate creates a DISI (dorsal intercalated segment instability) deformity.
- Scaphoid flexed and lunate extended
- Can progress to capitolunate joint (capitate and lunate carpal bones).
X-rays
- PA views demonstrate scapholunate widening (separation > 3mm), joint space narrowing between the scaphoid and radial styloid and sclerosis (increased bone density/hardening).
- Lateral views demonstrate DISI deformity (flexed scaphoid and extended lunate).
Radiolunate joint is spared

Treatment

Non-surgical

Rest, activity modifications, bracing, ice and NSAIDs (ibuprofen)
Corticosteroid injection

Surgical

Reconstructive surgery involves excising the scaphoid and arthrodesis and is indicated when non-operative treatment fails.