SLAC Wrist

Definition

SLAC Wrist

 

Scapho-lunate advanced collapse

- caused by malalignment of scaphoid on radius

- due to scapholunate disruption

 

Most common cause of wrist OA

 

Pathology

 

1.  Radio-scaphoid degenerative changes

- from abnormal flexion of scaphoid

- scaphoid fossa is elliptical causing incongruence with flexion of proximal scaphoid

- loads scaphoid fossa of radius peripherally

 

2.  Radiolunate joint preserved

- lunate fossa and proximal lunate spherical and congruent

 

3.  Capitate under increasing load descends into gap

- increasing loads on capitolunate joint

- separation of scaphoid and lunate

- capitate shears off radial edge of lunate

- get destruction on both lunate and proximal capitate 

 

X-ray

 

OA radio-scaphoid joint

Preservation of radiolunate joint

 

Staging

 

1.  Styloid OA

 

Stage 1 SLAC Radial Styloid OA

 

2.  Scaphoid Fossa OA

 

SLAC CT

 

3.  Lunato-capitate OA

- capitate descends in SL gap

 

SLAC Lunate Capitate OA

 

4.  Pancarpal OA

 

DDx

 

SNAC

- preservation of scaphoid fossa and proximal scaphoid congruence

- arthritis at scapho-capitate joint

 

Management

 

Stage 1

 

Definition

- styloid OA

- degeneration between the radial styloid and distal pole scaphoid

 

Options

 

1.  Styloidectomy

- early disease can respond well to styloidectomy

- remove at level A / no removal of scaphoid fossa

 

2.  Scapholunate Reconstruction 

 

A.  Excise fibrous tissue and insert SL screw

- fibrous ankylosis

- remove screw at 12/12

 

B.  Bone blocks with ligament

 

Stage 2 

 

Definition

- scaphoid fossa OA

- OA extends to involve scaphoid fossa and proximal pole scaphoid

 

Options

 

A.  Scaphoidectomy & four corner fusion

B.  Proximal Row Carpectomy

 

Scaphoidectomy & Four Corner Fusion

 

Scaphoidectomy and 4 corner fusion

 

Theory

- fusion of lunate to capitate

- loading is through normal lunate fossa

- fusion of lunate-capitate can be difficult

- add hamate and triquetrum in so called 4 corner fusion

- greatly increases fusion rates

- seemingly no deleterious effects

- if leave out scaphoid replacement tends to drift into radial deviation

- can use scaphoid for bone graft (but may not be high quality)

 

Advantage

- increased stability comared with PRC

- increased ROM compared with total wrist arthrodesis

 

Approach

- universal posterior approach

- base of EPL (3/4 interval)

- can use Lister's tubercle for BG

- make window on radial side so as not to get late rupture of EPL

- denervate wrist / remove terminal branch PIN

- ligament sparing exposure / open capsule between dorsal intercarpal and radiocarpal

- closure ER under EPL at end of case

 

Technique

- resect scaphoid

- denude surfaces of lunate / capitate / hamate / triquetrum

- use good quality BG from distal radius

- must reduce the lunate out of extension or will impinge dorsally

 

Scaphoidectomy 4 corner Fusion APScaphoidectomy 4 corner Fusion Lateral

 

Fixation

- headless compression screws

- dorsal circular plate

- K wires

 

Results

- strength 75-80% normal

- ROM 40 - 60% of normal

 

B.  Proximal row carpectomy

 

Proximal Row Carpectomy

 

Aim

- for capitate to articulate with distal radius

 

Disadvantages

- proximal capitate often devoid of good cartilage

- discard good lunate cartilage

- weakness ensues due to lengthening of tendons

- reported pain / instability / degeneration

 

Indications

- probably best in low demand patients

- not in stage 3 SLAC

 

Technique

- perform through standard dorsal approach

 

Results

- RCT of 4 corner fusion v PRC are comparable

 

Stage 3 

 

Definition

 

Capito-lunate OA 

- capitate migrates proximally between the scaphoid and the lunate

 

Options

 

A. Scaphoid excision & 4 corner fusion

B. Proximal Row Carpectomy

C. Wrist Arthrodesis

 

Note

- PRC may be bad options in stage 3

- they depend on the capitate and by definition the capitate is arthritic

 

Stage 4

 

Definition

 

Collapse / pancarpal OA

 

Options

 

Wrist arthrodesis