If the middle joint of a finger is in extended (bent back) position more than normal and also the end joint is in flexed (bent down) position, than it is known as swan neck deformity.
Pathophysiology: The intercalated joint collapse in the concept of Landsmeer which means that collapse of a joint in one direction and it will result in deformity of the next distal joint in the opposite direction. It’s kind of “Z” deformity.
Swan neck classification:
- I: PIP joint flexible in all positions
- II: PIP motion limited.
- III: Fixed PIP joint contracture but x-ray is okay
- IV: X-ray shows arthritic changes
Causes:
The most common cause of swan neck deformity is rheumatoid arthritis. Other possible causes are given below-
- Other types of arthritis.
- Untreated mallet finger – a condition often caused by injury.
- Poorly healed fracture in the finger.
- Other direct trauma to finger that has weakened the ligaments surrounding the PIP joint.
- Nerve damage that causes muscle spasms.
- Severely jammed tip of finger.
- Tightened hand muscles due to injury.
- Looseness of the fibrous plate inside the hand located at the base of the fingers.
- Loose finger ligaments.
- Ruptured finger tendon or tendons.
- Some genetic conditions, such as Ehlers-Danlos syndrome.
Sign & Symptoms:
- Pain
- Swelling of the PIP joint
- Laxity of the volar plate
- Snapping and locking of the fingers
- Hyperextension of the PIP and flexion of the DIP
Diagnosis:
- Rheumatoid arthritis (RA)—most common cause of swan neck deformity
- Chronic inflammation loosens the volar plate, making PIP susceptible to hyperextension
- As a result, extensor tendon tightens causing DIP to pull into flexed position
- Other findings: X-ray.
Treatment:
Manual:
- Restore flexibility to the PIP joint.
- Aligning the hand and finger.
- Should fix the DIP joint.
- Joint mobilization.
- Stretching exercises
Using splints.
Electrical:
- TENS
- UST
- IRR
- HIL
Surgical:
- Soft tissue surgery
- Finger joint fusion
- PIP joint arthroplasty