A SLAC or SNAC wrist is arthritis that follows an old injury to the scaphoid, one of the small wrist bones. Either its ligament to the neighbouring lunate tore and was never repaired, or the scaphoid broke and never healed. In both cases the bones slowly collapse and the cartilage wears in a predictable sequence. The wrist becomes painful, weak and stiff, often decades after the injury. Many people manage for years with a splint and the occasional injection. Where that is no longer enough, there are reliable operations that take the pain away while keeping useful movement in the wrist.
What is a SLAC or SNAC wrist?
The wrist contains eight small bones in two rows. The scaphoid bridges both rows and is held to the lunate by the scapholunate ligament. If that ligament tears and is not repaired, or the scaphoid fractures and does not heal, the scaphoid tips out of position.
The cartilage then wears in stages: first between the radius and the tip of the scaphoid, then the whole radioscaphoid joint, then between the lunate and the capitate. The joint between the radius and the lunate is spared until late, and every operation for this condition relies on that spared joint.
SLAC stands for scapholunate advanced collapse, after a ligament tear. SNAC stands for scaphoid nonunion advanced collapse, after an unhealed fracture.
Symptoms
- A deep ache in the wrist, worse after use and at the end of the day
- Pain on the thumb side of the wrist when it is bent back under load
- Stiffness, with loss of wrist bending in both directions
- Weakness of grip
- Clicking or grinding with movement
Causes and risk factors
- A scapholunate ligament tear that was missed or not repaired. See our page.
- A scaphoid fracture that did not heal, often one that was never diagnosed. See our scaphoid fracture page.
- Time. The collapse takes years, and many people present decades after the injury.
- Heavy manual work and sport, which load the wrist and bring the symptoms forward.
How it is diagnosed
By examination and X-ray. The examination shows where the wrist is tender, how much movement remains and how strong the grip is. The X-ray shows the collapse of the scaphoid and which joints are worn, which gives the stage, and the stage drives the choice of treatment.
A CT scan shows bone detail, including an old scaphoid nonunion, and an MRI shows the cartilage. Where an operation is being planned, wrist arthroscopy lets the surgeon inspect the cartilage directly through small incisions, which is the most accurate way to decide which joints can be kept.
Non-surgical treatment
Most people start here, and many stay here for years.
Splinting and activity change
A wrist splint worn during heavy tasks takes load off the worn joints. Changing how you lift and push reduces what the arthritis costs you without changing it.
Hand therapy
Our therapists fit the splint, teach joint protection and maintain the movement you have. Having therapy on site means this starts the same week.
Corticosteroid injection
An injection can settle a painful flare and buy months of comfort. We arrange these under ultrasound guidance rather than injecting in the rooms, and we would not repeat an injection more than twice at the same site.
When surgery is needed
Surgery is for pain that is no longer controlled and is limiting what you do. The principle is the same in every operation: remove the worn joint surfaces and keep the spared joint between the radius and the lunate. The choice depends on the stage and on the cartilage on the head of the capitate.
The operation
In early stages, arthroscopic trimming of the worn tip of the radius can be enough for a time.
A proximal row carpectomy removes three bones from the first row of the wrist: the scaphoid, the lunate and the triquetrum. The capitate then sits in the cup of the radius, forming a new, simpler joint. It suits earlier stages, where the head of the capitate still has good cartilage. No bone has to heal and the recovery is quicker.
A four corner fusion removes the scaphoid and fuses the lunate, capitate, hamate and triquetrum into one block, using bone from the removed scaphoid and a small plate or screws. The block moves on the spared radiolunate joint. It is the operation for more advanced stages, where the capitate cartilage is worn, and the bones need six to eight weeks to join.
Where the wear involves the whole wrist, a total wrist fusion or a wrist replacement is discussed instead.
Both are performed through an incision on the back of the wrist under a general anaesthetic with a local anaesthetic block for comfort afterwards. A carpectomy is a day surgery procedure taking approximately 60 to 90 minutes. A fusion takes approximately 90 to 120 minutes and is a day surgery or overnight procedure. A tape bandage covers the sutures under a plaster backslab.
Recovery, week by week
The two operations share the first fortnight and then diverge, because a fusion has to heal before it can be loaded.
Day of surgery. Your arm may feel numb or tingly for up to 24 hours from the block. You can move your fingers before you leave hospital. The wrist is in a plaster backslab.
Days 1 to 10. Keep the plaster clean and dry. Elevate the hand. Move your fingers, elbow and shoulder regularly.
Days 10 to 14. Review, and the sutures are removed. The backslab is replaced with a custom made removable wrist splint. After a carpectomy, gentle wrist movement starts now. Office work in the splint from about two weeks.
Four to six weeks. After a carpectomy the splint is weaned and therapy progresses to light use. After a fusion the splint stays on and X-rays check that the bones are joining.
Six to twelve weeks. After a carpectomy, strengthening and most daily tasks; driving from about six weeks. After a fusion, a CT scan at three months confirms union, then the splint stops and driving and loading begin.
Three to six months. A graded return to heavier work and sport. Heavy manual work from about three months after a carpectomy and four to six months after a fusion.
Up to twelve months. Grip strength and stamina keep improving. The wrist stays stiffer than before.
Risks and complications
Surgery for a SLAC or SNAC wrist is safe and routine, and complications are uncommon. They can include:
- Wound healing problems or infection.
- Bleeding or bruising.
- Nerve injury. Small sensory nerves run close to the incision, and irritation causes numbness or tingling over the back of the hand, which usually settles.
- Stiffness. Some loss of movement is part of both operations.
- After a fusion, the bones failing to join, which may need further surgery with more bone graft.
- Irritation from the plate or screws, which occasionally need removing.
- Arthritis in the new joint over the years, which can eventually need a total wrist fusion.
When to be seen sooner
Contact us, or see your GP, if you have:
- Wrist pain after an old injury that is now waking you at night or limiting your work
- A sudden increase in pain or swelling in a wrist that was previously manageable
- Redness, spreading pain or fever after an injection or an operation
If you have had surgery with us and have questions or concerns afterwards, phone the rooms during office hours on (08) 7127 0365.
Frequently asked questions
Will I lose movement in my wrist?
Some, after either operation, but most people keep roughly half to two thirds of normal wrist movement, which is enough for almost all daily tasks. The painful end of the range was not usable anyway.
Which operation will I have?
That is decided together. The stage on X-ray and the cartilage on the head of the capitate decide whether a carpectomy is still an option. Where the capitate is worn, a four corner fusion is the reliable choice.
Will the pain go completely?
The arthritis pain settles reliably, because the worn surfaces are gone. The wrist does not become normal: it becomes comfortable, stiffer than it was, and strong enough for most things.
When can I drive and go back to work?
The timing is in the table above and differs between the two operations. There is no legislation covering surgery and driving, so the test is whether you can control the car safely, including in an emergency. We will give you a realistic estimate for your specific job, and a certificate.
What does the surgery cost?
You will receive written informed financial consent setting out the surgeon, anaesthetist and hospital fees, your Medicare rebate and your health fund's contribution after your consultation and before anything is booked.
Do I need a referral?
Yes, for a consultation with one of our surgeons: a referral from your GP or another specialist is needed to claim the Medicare rebate. You do not need a referral to see one of our hand therapists for a splint or an assessment.
Written and clinically reviewed by Dr Paul van Minnen, MD, PhD, EBOPRAS, FRACS (Plast)
Last reviewed 8 November 2026