Dr Steve Carter
SNAC & SLAC Wrists
Scaphoid Non-Union Advanced Collapse and Scapolunate Advance Collapse is degenerative osteoarthritis of the wrist as a result of:
- Scaphoid Non-Union; or
- Scaphoid ligament rupture which has not been treated.
In the event of a scaphoid non-union or scapholunate ligament not being treated, the wrist inevitably and predicably starts to degenerate. This osteoarthritis can start to develop anything from 3 to 5 years of the initial injury. Very often these are young patient who now have a major problem with their wrists.
This degenerative osteoarthritis occurs because for normal wrist function the scaphoid and lunate are firmly linked and move and act as a functional unit. With a Scaphoid non-union or scapholunate ligament injury the scaphoid and lunate are now not linked. They are uncoupled from each other, like a train uncoupling a carriage. They now move in different directions resulting in instability of the wrist and subsequent osteoarthritis.
The patient presents with a history of having had a fall sometime in the past, usually on an outstretched hand. They now have pain, usually on the radial side of the wrist, decreased range of movement, particularly extension of the wrist. Loss of power and grip in the hand and wrists. They may have a feeling of instability or a clunck in the wrist.
Diagnosis is by physical examination. There will be decreased range of movement. There may be some swelling, particularly over the radial and dorsal side of the wrist. Tenderness in the anatomical snuffbox. A positive Watson shift sign if there is a scapholunate ligament injury.
The examination is followed by plain film xrays of the wrist. In SNAC wrist, the scaphoid non-union is pretty obvious and in the SLAC wrist, there is often a widened scapholunate gap >3mm, so called Terry Thomas sign.
In both the SNAC & SLAC wrists the wrists drop into a DISI deformity (dorsal intercalated segmental instability). This is the instability pattern we were talking about above, where the scaphoid and lunate are no longer connected either by fact of a non-union or a ruptured scapholunate ligament.
The rest of the xray follows a predictable pattern based on the osteoarthritis.
Stages of osteoarthritis
- Stage I – Radiostyloid osteoarthritis
- Stage II – Radioscaphoid osteoarthritis
- Stage III – Midcarpal osteoarthritis
- Stage IV – Generalised Wrist osteoarthritis
The treatment is obviously tailored to the stage of the arthritis. The patients often present only when they have stage III osteoarthritis.
In stages I & II, conservative measures such as a wrist splint and anti-inflamatories often accompanied with an intra-articular wrist injection, may alleviate the symptoms.
Remember once you have developed osteoarthritis there is no going back, so all our treatments are really salvage attempts to relieve the pain and improve function. Surgery in stages I and II may involve a radial styloidectomy if indicated. This is where a small part of the radial styloid is excised to prevent the scaphoid from rubbing on the styloid.
Once stage III is reached, if conservative splint and wrist injections fail, salvage surgery is indicated. This is either a partial wrist fusion where the scaphoid is excised and a four corner fusion is done, or a proximal row carpectomy is done. Whereby the arthritic proximal row of carpal bones is removed and the capitate now articulates with the lunate fossa.
Once stage IV is reached, there are no longer any salvage surgery options and the patient requires a full wrist arthrodes