Running down from the muscles of the forearm to the fingers are tendons that eventually flatten and branch out over the top of the finger to connect with the middle and end bones of each finger. When the extensor muscles in the forearm contract they pull on the extensor tendon and straighten the finger.
Within each finger joint are ligaments, bands of strong, elastic tissue that hold bones in position and allow for limited movement. The strongest ligament in the PIP joint is the volar plate, which prevents the PIP joint overextending and getting damaged. If the volar plate does become damaged or weakened, Swan Neck Deformity can occur.
Causes:
Any condition that loosens the PIP joint can lead to Swan Neck Deformity. Rheumatoid arthritis is a common culprit as the chronic inflammation of the joint stretches the volar plate. The more the volar plate stretches, the more the joint can hyperextend. This causes the DIP joint to be pulled downwards, leading to the characteristic bent finger shape of Swan Neck Deformity.
Other causes can include trauma to the muscles of the hand and fingers, or conditions such as Parkinson's disease, stroke, or cerebral palsy.
Symptoms:
Pain and swelling of the PIP joint
Bent base of finger, straight middle joint, and bent fingertip
Diagnosis:
A diagnosis of Swan Neck Deformity is usually apparent from a physical examination. To check the condition and alignment of the finger joints, or to rule out a fracture, an X-ray may be taken.
Treatment:
If the PIP joint is supple, non-surgical treatment may be successful. The finger must be properly realigned and the joint restored to its normal range of motion.
Treatment normally consists of wearing a splint for six weeks that prevents the joint hyperextending while still allowing it to bend. Physical therapy to restore joint flexibility is also important. If these measures fail to resolve the condition, surgery may be considered.
Surgery for Swan Neck Deformity is not always successful but consists of releasing the tissues around the PIP joint and realigning them in balance with all the finger structures. Occasionally, if the PIP joint is stiff, the joint has to be completely replaced. Another option for chronic Swan Neck Deformity is fusion of the DIP joint. This makes the joint stable, but obviously eliminates the ability of the joint to move.
Stretching and strengthening exercises are important components of rehabilitation. After surgery you would wear a splint for 3-6 weeks, and then begin therapy to gradually increase the joint's range of motion, followed by stretching and strengthening exercises.
Exercises:
Finger Abduction and Adduction:
Standing up, bend your elbow to a 90-degree angle. Rest the arm of the affected finger against your body. Spread your fingers as wide as you can. Hold for 5 seconds then bring them back next to each other. Do 10 repetitions for 1 set. Do 3 sets a day.
Finger Flexion:
Place the elbow of the affected arm on a flat surface, for instance a table, and lift your forearm straight up. Slowly bend one finger at a time to touch your palm, holding for 5 seconds as each finger is fully bent. Do 10 repetitions for 1 set. Do 3 sets a day.
