Swan neck deformity is a hand deformity in which your fingers are bent abnormally. Your finger’s middle joint bends back more than usual. The tip of your finger is bent down.
Swan neck deformity only affects your fingers. Your thumb isn’t affected, as it has one less joint than your fingers.
Swan neck deformity should not be confused with boutonniere deformity. In this condition, your finger’s middle joint won’t straighten, and your fingertip bends backward. The middle joint is “buttonholed” or pushed out like a button through a buttonhole between the bands of tendon that run along your finger.
What Are the Signs of Swan-Neck Deformity?
Signs that you have swan neck deformity finger include:
- Stiff finger
- Snapping feeling when you move your finger
- Problems bending your middle joint
Your doctor may classify your swan neck deformity according to its severity:
- Type I - Proximal interphalangeal (PIP) or middle joint is flexible in all positions.
- Type II - Middle joint can be bent in certain positions.
- Type III - Middle joint bending is limited in all positions.
- Type IV - Middle joint is stiff and there’s extreme damage to the joint cartilage.
What Are the Causes of Swan-Neck Deformity?
Swan neck deformity is usually caused by weakness or tearing of the ligament in the middle joint. In some cases, the tendon is torn and weakened. Over time, it gets harder for your tendons to straighten the joint. This causes the joint to bend abnormally.
Rheumatoid arthritis can lead to swan neck deformities (and boutonniere deformity) over time. In this autoimmune disorder, joints become inflamed, leading to pain and deformity of the joints.
Other possible causes of swan neck deformity include:
- Ruptured finger tendon
- Fracture in your finger that heals poorly
- Muscle spasm caused by nerve damage (muscle spasticity)
- Loose fibrous plate inside your hand
- Loose finger ligaments
- Untreated mallet finger
- Other types of arthritis
What Is the Treatment for Swan-Neck Deformity?
Swan neck deformity treatment depends on the severity of your condition. There are nonsurgical treatments such as:
- Hand therapy
- Extension block splints that may correct the excessive movement of your middle joint
- Progressive extension splinting that may help with the flexibility of your distal interphalangeal joint (DIP), the joint closest to your fingertip
Surgical treatment may involve replacing the joint or repositioning your tendons. It may include:
Soft tissue surgeries. If you’re at the early stages of the deformity, soft tissue surgeries may be done. These soft tissues include your ligaments and tendons.
One type of soft tissue procedure is flexor digitorum superficialis (FDS) tenodesis. This surgery helps stabilize the ligament that joins your finger bones (volar plate). This prevents your joint from hyperextending, or moving beyond what is normal.
Joint arthroplasty. This surgery involves the replacement of your finger joint with an implant. These implants may be made of special types of plastic, metal or carbon-coated materials. The implants will help your finger move with little to no pain.
Arthrodesis. This is also known as joint fusion surgery. Your surgeon will fuse the joint in your finger so it won’t move. Some flexible wire may be inserted into your finger to stabilize it. This surgery may be needed when your swan finger deformity and joint cartilage damage are severe.
You may need months to recover from hand surgery. After surgery, your hand may need to be immobilized in a splint. It’s likely that you may need to have hand therapy for several weeks or months.
Even after therapy and surgery, however, you may still have some limitations in your range of motion. Some people may still have some degree of deformity.
