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.