What is Scapholunate Advanced Collapse?
Scapholunate advanced collapse (SLAC) is a specific type of degenerative wrist condition that worsens over time, causing instability, deformity, and arthritis in the main and middle joints of the wrist. This pattern of injury and increasing instability occurs after a long period of separation between two specific wrist bones, the lunate and the scaphoid. More often than not, SLAC is the final result of an injury to the Scapholunate Interosseous Ligament (SLIL) in the wrist, which wasn’t treated properly.
When this condition is assessed through x-rays, CT scans, and MRIs, doctors often see a widening gap between the scapholunate bones, signs of damage to these bones, and shifting of another bone in the wrist, called the capitate. To understand the severity of the condition, doctors often classify it into four stages.
The most common treatments include various types of surgical procedures, such as corner joint fusion, capitolunate joint fusion, radial styloidectomy, proximal row carpectomy, and scaphoidectomy. This condition was first identified by Watson and Bellet after reviewing 4000 wrist x-rays and noticing a frequent pattern of arthritis in 210 of these wrists.
What Causes Scapholunate Advanced Collapse?
Chronic injuries to the SLIL, which is a ligament in the wrist, usually happen because of some sort of trauma. But, they also can be associated with other conditions that cause the wrist to break down over time or become inflamed. A condition called SLAC wrist can even happen in both wrists at once without any previous injuries, and it has been linked to a long-term condition called pseudogout.
Many times, these wrist issues aren’t properly identified at the beginning and might just be diagnosed as a simple “wrist sprain.” This is especially common among football linemen who are very likely to repeatedly injure their SLIL. This is because of the high-impact, bending movements they make with their wrists over several years.
These injuries can change how the wrist joint functions, which can cause arthritis in the wrist. If SLAC arthritis gets worse and an untreated injury to the SLIL continues to get worse, one of the bones in the wrist, the scaphoid, changes its shape and position. This can lead to more pressure on another bone in the wrist, the capitate, which ends up moving between the lunate and scaphoid bones over time.
Risk Factors and Frequency for Scapholunate Advanced Collapse
SLAC, which stands for Scapholunate Advanced Collapse, is the most frequently occurring age-related condition affecting the wrist. Damage to a particular ligament in the wrist, called the scapholunate ligament, happens in about 10% to 30% of events when the lower part of the radius bone in the wrist breaks.
- SLAC is the most frequent degenerative wrist condition.
- 10% to 30% of distal radius fractures (wrist fractures) involve damage to the scapholunate ligament.
- Studies show that patients with SLAC are often male, have had wrist trauma, engage in manual labor, and tend to be younger in comparison to patients with other joint conditions, like carpometacarpal osteoarthritis.
Signs and Symptoms of Scapholunate Advanced Collapse
If someone falls onto their hand with it stretched out, they might injure a part of their wrist called the SLIL, or Scapholunate Interosseous Ligament. This injury can occur on its own or accompanied by a fracture in the radius bone in the forearm or the scaphoid bone in the wrist. In fact, about 30% of fractures in the radius bone also involve damage to the SLIL region. But wrist trauma isn’t the only cause; SLIL injuries can also happen from falls onto other parts of the same arm – such as the elbow – from inflammatory arthritis, or due to accidental damage during surgery to remove certain types of cysts.
Patients with an injured SLIL might feel some pain, but not always. When they do feel pain, it often gets worse with heavy use and can be accompanied by a weird clunking sensation during movement. Other signs might include a decrease in the range of movement in the wrist and a weaker grip.
Looking at the wrist won’t necessarily reveal a SLIL injury; even with fresh injuries, there might not be a lot of swelling. However, when the ligament damage has led to something called scapholunate advanced collapse, any provocative movements will usually cause pain. In such cases, a health professional might use a test called the scaphoid shift test to check for abnormal movement of a bone in the wrist, which recreates the patient’s pain. A positive result indicates a likely SLIL injury.
The scaphoid shift test involves applying firm pressure to a particular part of the scaphoid bone while moving the wrist from side to side. In a normal wrist, the scaphoid can’t bend because of the pressure from the tester’s thumb. A positive result comes when the scaphoid snaps back into place when the tester stops applying pressure.
Another test called the scapholunate ballottement test can also be performed. This involves holding the lunate bone firmly in place while the other hand moves the scaphoid bone. If the test brings about pain, a grinding sensation, or too much movement of the scaphoid, it’s a positive result, indicating a possible SLIL injury.
Testing for Scapholunate Advanced Collapse
If your doctor suspects that you may have an issue with your wrist, such as SLAC (Scapholunate Advanced Collapse), they will likely begin with standard X-ray images. X-rays can show the bones and joints in your wrist; sometimes the doctor may ask you to make a fist to compare both hands. This can reveal abnormalities such as a ‘DISI’ (Dorsal Intercalate Segment Instability) – meaning that some of the bones in your hand may be unevenly spaced or angled. The changes in the wrist bones positioning are better spotted in the early stages of the disease.
As SLAC progresses, it goes through various stages that can be seen on an X-ray:
- Stage I – Arthritis starts to develop at the base of the thumb side of the wrist (near the ‘styloid’ bone).
- Stage II – Arthritis affects the entire region of the wrist where a small, boat-shaped bone called the ‘scaphoid’ connects to the wrist (the scaphoid fossa).
- Stage III – Arthritis extends to the joint between two other hand bones, the ‘lunate’ and ‘capitate’.
At this point, you may hear your doctor refer to a ‘Terry Thomas sign’ – where the space between the bones in your wrist is wider than usual, similar to the gap in the British comedian Terry Thomas’s teeth. As the disease progresses, you might notice your wrist bones changing position, but the main wrist joint (the ‘radiolunate’ joint) usually remains in good shape until the later stages.
The fourth stage (Stage IV) is when the disease has spread to all wrist bones. Initially, it was thought that the disease does not progress to this stage, but recent studies have found that up to 80% of SLAC patients may experience this widespread arthritis.
The doctor might prefer not to use CT scans, and MRI scans are usually not necessary either, as X-rays can typically provide sufficient information. However, in more difficult cases, an MRI might be ordered. This can reveal further details, such as thinning of the bone surfaces, inflammation in the joints of the wrist, and other abnormal changes in the bones of the wrist.
Treatment Options for Scapholunate Advanced Collapse
Treating Scapholunate Advanced Collapse (SLAC), a type of wrist condition, can be complex and is not always straightforward. For milder cases, non-operative treatments can include anti-inflammatory medications, wearing wrist splints, and possibly receiving corticosteroid injections which can help to reduce inflammation and pain.
There are also multiple surgical options for this condition, which are generally chosen based on the severity or ‘stage’ of the condition. These options include radial styloidectomy, proximal row carpectomy, scaphoid excision and four-corner fusion, full wrist fusion, and wrist joint replacement.
In early-stage SLAC (Stage I), surgery can include removal of part of the wrist bone (Radial Styloidectomy) and procedures to stabilize the small wrist bone known as the scaphoid. In mid-stage SLAC (Stage II), a procedure called a proximal row carpectomy, which involves removing some of the wrist bones, may be used. It’s important to note that this procedure is typically not effective for later stage disease (Stage III).
For late-stage SLAC (Stage III), options include removing the scaphoid bone and connecting four wrist bones together (4-corner fusion), which tends to have equally good outcomes as the proximal row carpectomy used in stage II SLAC. Another option is a wrist fusion, a procedure used when the disease has affected most or all of the wrist and involves fusing all the wrist bones together. While this can relieve pain, it does affect the range of wrist motion.
There are various ways to fix the bones in the 4-corner fusion procedure. A recent review showed no difference in healing rates or significant difference in range of motion and grip strength among the various fixation options. Meanwhile, long-term outcomes of 4-corner fusion generally show good satisfaction and a low probability of needing further surgery.
There has been ongoing debate about whether proximal row carpectomy or 4-corner fusion is the better treatment for mid to later stage(II/III) SLAC wrists. Some reviews suggest that outcomes are similar for these two procedures. However, in some cases, the type of procedure chosen may be based on patient factors, such as smoking history or age.
New procedures are actively being researched to preserve wrist motion in patients with SLAC wrists. For example, a recent study described a successful new procedure that uses tendon grafts to replace the affected row of wrist bones. Other new techniques being explored include 3-corner fusion, arthroscopic tendon interposition and 2-corner fusion.
It’s important to note that the decision about which treatment to use will depend on the individual patient’s condition, preferences, and overall health, and should be made with the advice of an experienced healthcare provider.
What else can Scapholunate Advanced Collapse be?
When a doctor is trying to find out what’s causing wrist pain and believes it could be SLAC (Scapholunate Advanced Collapse) wrist or SLIL (Scapholunate Interosseous Ligament) injury, they consider many possible diseases or conditions that could be causing the pain. These include:
- Broken or fractured scaphoid bone (one of the wrist bones)
- Fracture of the lower end of the radius bone (near the wrist)
- Dorsal ganglion cyst (a noncancerous lump filled with jelly-like fluid)
- Septic arthritis (joint inflammation due to a bacterial or fungal infection)
- Avascular necrosis of the scaphoid (death of bone tissue due to lack of blood supply)
- Gout (a type of arthritis caused by too much uric acid in the blood)
- Pseudogout (a type of arthritis caused by calcium pyrophosphate dihydrate crystal deposits in the joints)
- Rheumatoid arthritis (a long-term autoimmune disorder that primarily affects joints)
- Tearing of the triangular fibrocartilage complex (a cartilage structure located on the side of the wrist away from the thumb)
- Kienbock’s disease (a condition where the blood supply to one of the small bones in the wrist is interrupted)
- Tenosynovitis (inflammation of the fluid-filled sheath that surrounds a tendon)
- Lunate fracture or dislocation (damage to another wrist bone)
- Dorsal intercalated segmental instability (a condition that results in the abnormal alignment and motion of the wrist bones)
Conditions like gout and pseudogout, which are known as crystalline arthropathies, can actually lead to SLAC wrist.
What to expect with Scapholunate Advanced Collapse
Scapholunate advanced collapse generally starts with a gradual loss of stability in the carpal bones that surround the lunate bone in the wrist. This typically happens after an injury where the wrist is excessively extended, bent towards the side of the pinky, and the middle part of the wrist is twisted. Despite the complex nature of this condition, the outcome after surgery is usually positive. Based on one study, a great majority of the patients, specifically 91% were satisfied with their surgery results and said they would undergo the procedure again. Furthermore, 80% of them were able to return to work.
Possible Complications When Diagnosed with Scapholunate Advanced Collapse
There can be complications from surgical procedures such as possible infection, failed bone fusion, and the need for additional procedures. In a study conducted by Ashmead and his team on 100 patients who underwent surgery for SLAC (Scapholunate Advanced Collapse) of the wrist, they found that on average, patients had a 53% range of motion in flexion and extension, and 80% grip strength compared to the uninjured wrist.
Around 3% of patients did not have successful bone fusion, but all of these cases were cured after performing bone graft revision surgery. Other studies have shown a nonunion rate of 4.3%.
In another comprehensive review, the top complication reported was dorsal radiocarpal impingement. This happened in 4.4% of the cases, contributing to an overall complication rate of 13.5% for SLAC surgeries.
Some Common Complications to be Aware of:
- Potential infection
- Failure of bone fusion
- Need for additional procedures
- Dorsal radiocarpal impingement
Recovery from Scapholunate Advanced Collapse
After a surgery called a 4-corner fusion, patients need to wear a special support, known as a short-arm volar splint, for two weeks. After this period, a personalized splint is worn for another six weeks or until X-rays show that the area is healed.
Gentle finger exercises and strengthening can begin after two weeks, but exercises for the wrist and strengthening should not start until X-rays confirm the area has fully healed. Patients should be aware that they may experience a 50% loss in wrist movement compared to their other wrist. Also, the strength of their grip should return to about 80% of their unaffected hand’s strength.
Preventing Scapholunate Advanced Collapse
SLAC, which stands for Scapholunate Advanced Collapse, is a condition that usually affects the wrist due to a slow buildup of damage to a particular ligament known as the scapholunate ligament. When a person first visits their doctor for this, especially after the injury is identified using medical imaging (like an X-ray or MRI), it’s crucial for the doctor and patient to have a thorough talk. It’s important to explain that over time, this condition can lead to serious long-term problems, including the eventual structural breakdown, or collapse, of the wrist.
