Swan Neck Deformity

Swan neck deformity is a deformed position of the finger, in which the joint closest to the fingertip (DIP) is permanently bent toward the palm while the nearest joint to the palm (PIP) is bent away from it.

There are several causes of swan neck deformity, the most common causes are:

• Arthritis.
• Untreated Mallet finger.
• Direct trauma to the PIP joint.
• Nerve damage.
• Jammed fingertip. 
• Tightened hand muscles.
• Loose finger ligaments.
• Ruptured finger tendon or tendons.
• Genetic conditions like Ehlers-Danlos syndrome.
• Muscle spasms caused by nerve damage.

Swan neck deformity is easy to recognize the symptoms in the later stages.

   Symptoms include:

• Pain while bending the knuckle.
• Locking of the joint.
• Stiffness.
• Snapping sound when bending the finger.
• Two outer joints of the finger are bent, which resemble a swan's neck.
• Difficult to grasp an object or make a fist.
• Limited movement and loss of some fundamental functions of the fingers and hands.

Pathology

This Deformity arises from the DIP, PIP, or even the MCP joints. Swan neck deformity occurs due to abnormal stress on the ligament around the PIP joint of the finger. The stress causes the ligament to loosen, resulting in hyperextension of the PIP joint, causing the PIP joint to bow in towards the palm. And the joint furthest from the palm (DIP joint) forces the fingertip to point towards the palm. There is a stretching of the volar plate at the PIP joint that causes hyperextension and some damage to the attachment of the extensor tendon to the base of the distal phalanx which produces a hyper-flexed mallet finger. 

Physical examination:

The examiner does the visual examination of the hands, looks for a hyperextended middle joint (PIP), and checks whether the tip of the finger is flexing inwards to point towards the palm. Active and passive movements are assessed at the MCP, PIP, and DIP independently. In addition, to determine if a patient has a swan neck deformity, the examiner looks for other causes like rheumatoid arthritis.

Bunnell’s test:

To determine whether a patient is present with an intrinsic tightness or capsular restriction, Fianchetto-Bunnell littler test is performed by holding the MCP in an extended position while passively flexing the PIP, noting the available ROM. The same test is then repeated with the MCP flexed, if there is no change in motion between the two tests, then capsular restriction at the PIP joint is suggested. In case the motion increases when the MCP is flexed, then intrinsic muscle tightness is suggested.

X-ray:

An X-ray of the finger or fingers is used to determine if an acute injury may be the cause. X-ray is ordered to evaluate for articular disruption, even carpal collapse, or severe arthritis in the later stages.

Medication: NSAIDs, Disease-modifying anti-rheumatic drugs (DMARDs), analgesics, glucocorticoids, etc.

Note: Medication should not be taken without a doctor's prescription.

Surgery:

Severe cases of deformity that do not respond to conservative treatment, are most likely recommended for surgery. Surgical options available for swan neck deformity are soft tissue surgery, finger joint fusion, PIP joint arthroplasty, etc. 

Splints:

Extension block splints help to correct the hyperextension at the PIP joint. A progressive extension splint can help improve the DIP flexion deformity. A ring splint, also called a figure eight splint, is placed around the PIP joint to correct deformity in the initial stages for a few weeks. The advantage of a ring splint is that the finger can be bent down freely.

Stretching Exercises:

Hand therapy for passive stretching can be combined with splinting. This combination of treatments may increase flexibility and mobility at both the DIP and the PIP joints. Gently straighten the affected finger and hold for 5 secs at the apex of this finger extension. Perform 1 set of 10 repetitions 3 to 5 times per day to promote flexibility in the finger joints.

Strengthening Exercises:

Strengthening exercises help to maintain the range of motion, strengthen weak muscles, and improve function in the fingers and hands.

Range of motion Exercises:

Finger passive range of motion is recommended to maintain flexibility and range of motion in the fingertips.

Finger Flexion:

Place the affected hand's elbow on a flat surface, such as a table, and lift the forearm straight up. Slowly bend the fingers to the middle of the palm, one at a time. Hold for 5 secs at the apex of each finger flexion. To improve flexion and range of motion in the fingers, do 1 set of 10 repetitions 3 times a day.

Finger Extension:

Stand in front of the table, and place the affected hand on the table's surface with the palm flat and the fingers extended. Lift each finger as far off the table as possible, one at a time, hold for 5 secs at the apex of the finger extension, and then relax. Perform 1 set of 10 repetitions 3 times per day. Pick up small objects such as coins and marbles with the injured finger and thumb promotes joint health and flexibility in addition to finger extension, squeeze a rubber ball, and hold each squeeze for 5 secs will help the injured hand's range of motion and flexibility.

Finger Adduction and Abduction:

Stand tall and bend the elbow to a 90° angle. Spread the fingers as wide as possible by bringing the arm of the affected finger to the side of the body. Hold for 5 seconds before reuniting the fingers. Perform 1 set of 10 repetitions 3 times a day to increase the circulation of oxygenated blood to the fingers and improve joint health.

The patient is advised to restore the balance in the structures of the hand and fingers. Care should be taken to align the PIP joint and prevent hyperextension and restore the DIP extension. If it doesn't work then surgery may be needed.