Scapholunate dissociation is a wrist condition that is not widely known. It is often missed because it tends to occur with other injuries including wrist sprains and wrist fractures (broken bone). However, it can lead to chronic instability and pain if not treated. Read on to learn more about scapholunate dissociation. Let’s start with anatomy!
The wrist
The wrist is made up of 3 joints. These include the distal radioulnar joint, radiocarpal joint, and the midcarpal joint. The distal radioulnar joint is made up of the ends of the forearm bones, the radius and ulna, at the wrist. This joint is essential for supination and pronation. Pronation is rotating the forearm, so the palm faces downward, and supination is forearm rotation where the palm faces upward.
The radiocarpal joint is made up of the radius and the first row of carpals. Carpals are the small wrist bones in between the forearm bones and the hand bones. The first row of carpals is called the proximal row and includes the scaphoid, lunate, and triquetrum. This row is more mobile than the distal row. The radiocarpal joint is the dominant joint for wrist extension. It assists in wrist flexion, radial deviation, and ulnar deviation.
Wrist extension is when the back of the hand moves toward the back of the forearm. Wrist flexion is when the palm of the hand moves toward the forearm. Radial deviation is when the hand moves to the thumb side. Ulnar deviation is when the hand moves towards the little finger side.
The midcarpal joint is the joint made up of the first and second row of carpals. The second row of carpals is also called the distal row and includes the trapezium, trapezoid, capitate, and the hamate. This row is more stable than the proximal row of carpals. The midcarpal joint assists in wrist extension and ulnar deviation. It is the dominant joint for wrist flexion and radial deviation.
What is scapholunate dissociation?
Scapholunate dissociation is a widening gap that occurs between the scaphoid and lunate bones of the wrist. It is the result of an injury to the ligaments that hold the scaphoid and lunate in position. This is most likely the result of a fall on an outstretched hand. This is called a FOOSH injury.
Scapholunate dissociation occurs in up to 40% of all wrist fractures and in 5% of wrist sprains. The incidence of scapholunate dissociation is unknown because it is often overlooked by the more obvious wrist sprain or fracture that occurred during the injury.
This injury can also occur while gripping the steering wheel during a car accident. Those with hypermobile wrists and rheumatoid arthritis have an increased risk of of scapholunate dissociation.
Older adults are also more at risk for scapholunate dissociation. The ligaments that stabilize the wrist can have degenerative tears that occur over time. These tears are present in the ligaments that stabilize the scaphoid and lunate bones in 50% of people over the age of 80.
What are the symptoms of scapholunate dissociation?
There are several symptoms associated with scapholunate dissociation. These include:
- Pain in the anatomical snuff box – When the thumb is in the “thumbs-up” position, the scaphoid is located in the little hollow at the base of the thumb. This is called the anatomical snuff box.
- Clicking and/or catching at the thumb side of the wrist
- Pain at the thumb side of the wrist
- Pain with loading of the wrist – This includes pushing off of a chair or in push-up position.
- Weakness of the wrist with gripping
- Swelling and tenderness in the wrist
- Feelings of instability of the wrist
What are the complications of scapholunate dissociation?
There are two main complications of scapholunate dissociation. These include:
- Arthritis – This refers to general osteoarthritis that tends to occur over time to joints that have suffered previous injuries. Arthritis will occur if the scapholunate condition was or was not treated. Arthritis can cause stiffness, pain, and swelling at the wrist.
- Scapholunate advanced collapse (SLAC) – This refers to degenerative arthritis and deformity that can occur if the scapholunate dissociation was never treated. This can lead to chronic pain and severe disability at the wrist.
Will l need surgery?
The answer is probably. If the injury is recent, the ligament is only partially torn, and the scaphoid and lunate are not displaced, then it is possible that surgery can be avoided. The wrist will be in a splint or cast for several weeks. However, the majority of scapholunate dissociation will need surgery to correct the wrist instability.
Who should I see?
- Orthopedic hand specialist – If you have had a previous wrist injury (whether recent or in the past) and you suspect that you have scapholunate dissociation, then it is best to see an orthopedic hand specialist. Because of the potential complications, this injury should be treated quickly. The orthopedist can order imaging and inspect the wrist to determine the extent of the injury and advise on the best course of treatment.
- Physical therapist – Physical therapy will be needed to regain mobility and strength in the wrist after surgery. Because of the extended time in a cast or splint, the wrist will be stiff and sore when trying to move or use it. Your PT can evaluate you to determine the extent of your mobility and strength deficits and use manual therapy, as well as, stretching and strengthening to help address all problems in and around the wrist.
What can I do?
- Relative rest – Resting the area to decrease further pain and damage from occurring is one of the best ways to allow the wrist to heal. If you are not able to participate in your activity or sport, then you can supplement with non-irritating activities such as walking or jogging while your wrist is healing.
- Ice – Ice can help decrease pain and symptoms at the wrist. Ice the painful area for 15 to 20 minutes at a time. I would recommend using an ice pack several times per day if the pain is constant or is preventing you from participating in an activity. Ice immediately after activity.
- The following are activities that you can do after the cast or splint is removed and you are cleared by your surgeon.
- Wrist flexion and extension stretching – You will need to stretch out the wrist flexors and extensors. This will feel very tight and sore at first. Begin with a gentle stretch. You can stretch more aggressively as the soreness subsides. See the video below.
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- Wrist strengthening – It is important to strengthen the wrist after a long period of immobilization. Begin with low to no resistance and slowly increase as it becomes easier. You should have minimal pain when performing the exercise and no pain afterwards. Below is a video showing how to strengthen the wrist using resistance bands.
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- Grip strengthening – Strengthening the muscles for gripping is important since a scapholunate dissociation can affect this action. Performing gripping exercises is helpful for recovering hand strength. See the video below.
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- Strengthening the muscles around the elbow and shoulder – Strengthening the muscles around the elbow and shoulder are also important in being able to return to your activity. Decrease your resistance or number of repetitions if you are having pain in the wrists. Using loop resistance bands, dumbbells, or resistance bands can increase strength and difficulty. See the videos below.
In review
- The wrist is made up of 3 joints.
- These include the distal radioulnar joint, radiocarpal joint, and the midcarpal joint.
- Carpals are the small wrist bones in between the forearm bones and the hand bones.
- The scaphoid and lunate are one of the 8 carpal bones.
- They are in the proximal row of carpals and are important in wrist motion and stability.
- Scapholunate dissociation is a widening gap that occurs between the scaphoid and lunate bones of the wrist.
- It is the result of an injury to the ligaments that hold the scaphoid and lunate in position.
- This is most likely the result of a fall on an outstretched hand.
- There are several symptoms of a scapholunate dissociation including pain at the wrist, tenderness at the anatomical snuff box, and decreased wrist motion.
- This is a frequently missed diagnosis which could lead to long-term disability and pain.
- There are several complications that could occur including arthritis and SLAC.
- Surgery will probably be required.
- There are things that you can do.
- Rest
- Ice
- After surgery or cast is removed
- Wrist flexion and extension stretching
- Wrist strengthening
- Grip strengthening
- Elbow and shoulder strengthening
As always, If you have questions about the content of this post or any other musculoskeletal questions, please e-mail me.
Additional resources
https://www.physio-pedia.com/Scapholunate_Dissociation
https://www.orthobullets.com/hand/6041/scapholunate-ligament-injury-and-disi