SCAPHOLUNATE ADVANCED COLLAPSE (SLAC)

Question 1

4 key radiographic features on PA view

Answer 1

1. SL gap/ interval > 3mm (Terry Thomas sign)
2. Cortical/ signet ring sign = scaphoid flexion
3. Break in Gilula’s arcs
4. Proximal migration of capitate into SL space

Question 2

4 key radiographic features on lateral view

Answer 2

1. SL angle > 70deg (normal = 30-60)
2. Radiolunate angle > 15deg dorsal (normal = 0 +/- 10)
3. Capitolunate angle > 20deg (normal = 0 +/- 15)
4. Capitate subluxes dorsally on lunate due to CL instability

Question 3

Classification of SLAC wrist

Answer 3

Modified Watson classification = radiographic classification with 4 stages
Stage I = radial styloid arthritis
- radial styloid beaking on x-ray
Stage II = radioscaphoid arthritis
Stage III = capitolunate arthritis
- due to CL instability
Stage IV = pancarpal including radiolunate arthritis
- controversial stage = if radiolunate, suspect other cause

Question 4

Surgical options for SLAC wrist based on stage

Answer 4

Stage I = radial styloidectomy
Stage II = PRC/ scaphoid excision + 4CF
Stage III = scaphoid excision + 4CF/ wrist fusion (not PRC)
Stage IV = wrist fusion