Swan neck deformity is a condition that affects the joints in the fingers. It can lead to serious physical impairment.
It typically develops due to unusual stress on the volar plate, which is the ligament around the middle joint of the finger, or the proximal interphalangeal (PIP) joint. However, sustaining damage to any of the three finger joints can cause swan neck deformity.
The resulting shape looks similar to that of a swan’s neck, which is how the condition got its name.
In this article, learn more about swan neck deformity, including causes, symptoms, and treatments.
For swan neck deformity to occur, there must be unusual stress on the ligament around the PIP joint of the finger.
Simultaneously, the joint farthest from the palm, called the distal interphalangeal (DIP) joint, goes into flexion. This means that the finger bends at the joint, forcing the fingertip to point downward.
The bent fingers may make it difficult for a person with swan neck deformity to grasp objects or make a fist. A doctor may classify the limited motion as a disability, as the person has lost some fundamental function in the fingers and hand.
Some people may mistake similar finger malformations for swan neck deformity. These similar malformations include the duckbill deformity, which causes the thumb or fingers to form a 90-degree angle.
Although it is related to other deformities, swan neck deformity is distinct in that it can only affect the fingers, as the thumb lacks a middle joint.
Some other possible causes may include:
- untreated mallet finger
- a poorly healed fracture in the finger
- nerve damage that causes muscle spasms
- tightened hand muscles due to injury
- looseness of the fibrous plate inside the hand
- loose finger ligaments
- ruptured finger tendons
- some genetic conditions, such as Ehlers-Danlos syndrome
As a result, people who have recently received a diagnosis of rheumatoid arthritis may wish to contact a doctor to discuss some steps they can take to prevent swan neck deformity.
Swan neck deformity exclusively affects the fingers of the hand.
A person’s symptoms will typically change depending on the stage of their condition. They can include:
- Finger bending: Swan neck deformity may start with the bending of just one finger joint or a slight change in both.
- Joint pain: Another early symptom of swan neck deformity may be pain when bending the finger joints.
- Finger deformity: In the later stages of swan neck deformity, the symptoms are clearly recognizable. As the PIP joint hyperextends and the DIP joint flexes, the finger begins to resemble a swan’s neck.
Swan neck and Boutonniere deformities both affect the finger joints, but they do so in different ways.
Boutonniere deformity causes an extension at a person’s knuckle, flexion at their PIP joint, and extension at their DIP joint. This causes the finger to extend upward from the knuckle, downward at its central joint, and upward again at the fingertip.
Visually, Boutonniere deformity is the inverse of swan neck deformity.
Doctors can classify Boutonniere deformity in different types and stages. These are as follows:
- Type 1: The finger is flexible with a complete range of motion.
- Type 2: The finger is flexible with a restricted motion according to knuckle position.
- Type 3: The finger is stiff with normal PIP joint articular surfaces.
- Type 4: The finger is stiff with the destruction of PIP joint articular surfaces.
Rheumatoid arthritis is a common cause of both conditions.
Swan neck and Boutonniere deformities may both require surgery to correct.
Doctors diagnose swan neck deformity with a visual examination of the hands and a review of the person’s medical history. The doctor
They will also assess both the active and passive range of motion of the knuckle, PIP joint, and DIP joint. Active range of motion relates to what finger movements a person can perform on their own. Passive range of motion is the full range of the joint when under outside pressure.
The doctor may order an X-ray of the finger or fingers to determine the extent of any damage.
In addition to determining whether or not a person has swan neck deformity, the doctor will look to diagnose any underlying conditions and causes, such as rheumatoid arthritis.
A variety of treatment options exist for swan neck deformity. There are two broad categories of treatment: surgical and non-surgical.
The sections below look at these options in more detail.
Non-surgical treatment focuses on restoring flexibility to the PIP joint and aligning the hand and fingers. Fixing the PIP joint can also fix the DIP joint.
In some cases, a person
In addition to therapies or as a stand-alone treatment, a doctor may also prescribe special finger splints. These produce the best results when the PIP joints are most supple.
Due to the progressive nature of the condition, non-surgical treatments
Severe cases of swan neck deformity, as well as those that do not respond to therapies and splints, will likely require surgery.
- Soft tissue surgery: This involves releasing, aligning, and
balancing the ligamentsaround the PIP joint. After surgery, most people will receive physical therapy to aid recovery.
- Finger joint fusion: A doctor
may fusean affected joint to reduce its movement. Fusing a finger joint can stabilize it, reduce pain, and avoid further deformity. However, joint fusion can limit joint mobility.
- PIP joint arthroplasty: This involves
replacing part or allof the PIP joints in the affected fingers. A surgeon will remove and replace both ligament sections around the joint. Once the new ligaments are in place, the surgeon will typically reconstruct some of the soft tissue to help restore movement to the finger.
After surgery, a person may undergo continued physical and occupational therapies. These can help them gradually regain strength and mobility in the fingers.
Typically, a full recovery from swan neck deformity is
Swan neck deformity is the result of ligament and joint damage. Hyperextension of the middle finger joint forms a shallow “V” shape, while a flexion in the joint farthest from the palm points the fingertip downward. The resulting shape may resemble that of a swan’s neck.
Swan neck deformity can severely affect a person’s ability to carry out everyday tasks and may require surgery. In mild cases, a doctor may prescribe physical therapy and static supports to help treat the condition.
Rheumatoid arthritis, cerebral palsy, and physical trauma are the leading causes of swan neck deformity.