Scapholunate Dissociation

What is scapholunate dissociation?

Scapholunate (SL) dissociation is when the small bones in your wrist (scaphoid and lunate) move out of alignment. During SL dissociation, a gap forms between the bones. When you use your wrist, these bones move apart (dissociate) from each other.

Scapholunate dissociation usually occurs from an injury to the ligament connecting your scaphoid and lunate bones (scapholunate interosseous ligament).

You may need surgery to treat scapholunate dissociation. But proper treatment followed by physical therapy can help you recover fully.

Who might get scapholunate dissociation?

Scapholunate dissociation can affect anyone no matter their gender, ethnicity or race. But you’re at greatest risk of this condition if you fall on your hand.

How common is scapholunate dissociation?

Scapholunate dissociation occurs in about 5% of all wrist sprains. About 40% of all distal radius fractures, especially chauffeur fractures, include SL dissociation.

What causes scapholunate dissociation?

SL dissociation most often occurs from falling on an outstretched hand. This type of fall can tear your scapholunate interosseous ligament (SLIL).

Other causes of SL dissociation may include:

• Gripping a steering wheel during an auto accident.
• Hereditary spastic paraparesis.
• Loose ligaments (congenital ligament laxity).
• Rheumatoid arthritis.

What are the symptoms of scapholunate dissociation?

The main symptoms of SL dissociation include:

• Pain in the back of the wrist with strong gripping motion.
• Weakness in grip strength.
• Swelling and tenderness in the wrist.
• Wrist pain (when extending your wrist).

How is scapholunate dissociation diagnosed?

Your healthcare provider will ask about symptoms and examine your wrist for pain, swelling and tenderness. They may also do the following:

• Scaphoid shift test: Your provider puts pressure on your scaphoid and moves your wrist. This movement tests the stability of your scaphoid bone.
• X-ray: This diagnostic imaging X-ray shows the size of the scapholunate gap. SL dissociation gaps may be 5 millimeters (mm) or more. Normal gaps are 2 mm or less. Your provider may also see a “ring sign” on an X-ray due to the repositioning of your scaphoid.
• Magnetic resonance imaging (MRI): An MRI makes detailed images to help your provider confirm an SLIL tear.
• Arthroscopy: Arthroscopy uses a scope inserted in small incisions to look inside your joints.

How is scapholunate dissociation treated?

Scapholunate dissociation treatment first includes:

• Analgesics (painkillers).
• Splinting your wrist with a thumb splint to keep it from moving.

Your provider may refer you to a hand specialist. You will likely need hand surgery within six weeks of your injury.

Your surgeon may perform surgery while you’re asleep under general anesthesia. Or they may do it after numbing your entire upper extremity (regional anesthesia). They will:

1. Make an incision in the back of your wrist.
2. Clean out any damaged tissue.
3. Use your tendon or suture or a metal screw to close the gap between the scaphoid and lunate bones.
4. Close the incisions.

How can I reduce my risk of scapholunate dissociation?

You can reduce your risk of scapholunate dissociation by taking steps to prevent falls. These steps may include:

• Doing activities to improve your balance, coordination and strength.
• Keeping your home safe from tripping hazards (rugs, loose cords, poor lighting).
• Using assistive devices such as a cane or walker if needed.
• Wearing flat, sturdy shoes with good traction.

What can I expect if I have scapholunate dissociation?

If you don’t get prompt treatment for SL dissociation, complications may include:

• Chronic pain.
• Inflammatory arthritis.
• Joint instability.
• Reduced grip strength.
• Scapholunate advanced collapse (SLAC) wrist (when your wrist develops degenerative arthritis).

What is the outlook if I have scapholunate dissociation?

If you have surgery for SL dissociation, you’ll need to wear a cast for a few weeks. Once your provider removes your cast, physical therapy can help restore strength to your wrist. You can usually return to your normal activities within a few months.

How do I take care of myself with scapholunate dissociation?

After treatment for SL dissociation, talk to your doctor about what activities you can safely perform. Specific exercise programs can help you regain strength and range of motion in your wrist.

A note from Cleveland Clinic

Scapholunate (SL) dissociation happens when small bones in your wrist (scaphoid and lunate) misalign. SL dissociation occurs when you injure the ligament connecting these bones. Falling on an outstretched hand usually causes this condition. Symptoms include wrist pain, swelling and tenderness. Providers diagnose scapholunate dissociation with a scaphoid shift test, X-rays, MRI and arthroscopy. Treatment usually includes surgery. With proper treatment, most people with SL dissociation can return to their regular activities in a few months.