Swan Neck Deformity of the Finger

How swan neck deformity develops

Each finger has three joints. Straightening and bending are balanced by tendons on the back (extensor) and front (flexor) of the finger, held in place by ligaments. The volar plate, a strong ligament on the palm side of the middle joint, stops it from bending backward.

A swan neck deformity develops when this balance is lost:

• the middle joint hyperextends (bends backward)
• the extensor force shifts away from the fingertip, so the tip droops into flexion

The original problem can start at any of the three joints:

Causes and risk factors

• rheumatoid arthritis: the most common cause; joint lining inflammation stretches ligaments
• hand injuries, including mallet finger and jammed fingers
• generalized joint laxity: Ehlers-Danlos syndrome and hypermobility
• spasticity from cerebral palsy, stroke or brain injury
• lupus and psoriatic arthritis
• previous hand surgery

Symptoms

• a finger shaped like a swan's neck: middle joint bent backward, tip bent down
• difficulty starting to bend the finger, sometimes with a painful snap or catch as the middle joint "flips" into flexion
• weak grip and pinch
• difficulty with fine tasks such as buttons and writing
• pain and swelling with inflammatory arthritis

Stages (for rheumatoid arthritis, Nalebuff classification)

Diagnosis

A hand specialist examines how much each joint can move actively and passively, checks for tight intrinsic muscles, and looks for snapping. X-rays show arthritis or joint damage. Blood tests may be done if rheumatoid arthritis has not been diagnosed.

Treatment

Non-surgical

• Ring splints (figure-of-eight or silver ring splints) block the middle joint from hyperextending while allowing it to bend. They are often worn long term.
• Hand therapy: exercises to maintain motion and strengthen the hand, and guidance on joint protection.
• Treat the cause: splinting for mallet finger; disease-modifying medicines to control rheumatoid arthritis and reduce further joint damage.
• Pain relief with NSAIDs or acetaminophen, following the label, and steroid injections for inflamed joints.

Surgery

Considered when the deformity is fixed, painful or limits hand function:

• tendon and ligament rebalancing (such as reconstruction of the oblique retinacular ligament or tightening the volar plate)
• release of tight intrinsic muscles
• correction of the original mallet finger
• fusion of the middle or fingertip joint for damaged joints
• joint replacement of the middle joint in selected cases

Outlook

Flexible deformities often respond well to splints and therapy, especially when treated early. With rheumatoid arthritis, good disease control helps prevent progression. Fixed deformities can be improved with surgery, though full normal motion may not be restored.

Frequently asked questions

What causes swan neck deformity?

It is caused by imbalance of the tendons and ligaments around the finger joints. Rheumatoid arthritis is the most common cause. Others include untreated mallet finger, injury to the ligament at the front of the middle joint, loose joints and spasticity after stroke or cerebral palsy.

Can swan neck deformity be corrected without surgery?

Flexible deformities can often be managed with ring splints that stop the middle joint from bending backward, plus hand therapy. Splints do not cure the problem but improve function and comfort. Fixed deformities usually need surgery to correct.

What is the difference between swan neck and boutonniere deformity?

They are opposite positions. In swan neck deformity, the middle joint bends backward and the tip bends down. In boutonniere deformity, the middle joint bends down and the tip bends backward. Both are common in rheumatoid arthritis.

Is swan neck deformity painful?

It can be, especially when caused by inflammatory arthritis or when the finger snaps or catches during movement. Some people have little pain but find it hard to grip or pinch. Splints, medicine and therapy help reduce discomfort.