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Swan-Neck Deformity (SND) is a deformity of the finger, in which the distal interphalangeal joint (DIP) and the metacarpal phalangeal (MCP) is in flexion. While the proximal interphalangeal (PIP) is in hyperextension; it is caused by abnormal stress on the volar plate, the ligament around the middle joint of the finger (PIP joint), plus some damage to the attachment of the extensor tendon. The resulting shape looks similar to a swan’s neck, which is how the condition got its name. The boutonniere deformity can be mistaken for a swan-neck deformity. It is important to recognize that boutonniere deformity consists of hyperextension of the DIP and flexion of the PIP. Swan-neck deformity is just the opposite. SND can be caused by a variety of conditions such as rheumatoid arthritis (The most common), untreated mallet finger, various disorders such as cerebral palsy, stroke, Parkinson’s disease, psoriatic arthritis, scleroderma and hand trauma.
Signs and Symptoms
Symptoms include inflammation of the joints, stiffness in the fingers, and a gradual difficulty in bending the middle joint because of the location of the tendons. A snapping sensation can happen during bending.
There are many treatments available for this deformity, depending on the condition’s severity. There are two categories of treatment: surgical and nonsurgical.
Hand therapy for passive stretching combined with corrective splinting may benefit even chronic conditions. This combination of treatment may increase mobility and flexibility at both the DIP and the PIP joints. Extension block splints may help correct the hyperextension at the PIP joint. Progressive extension splinting can help improve the DIP flexion deformity. Although stretching and splinting may increase mobility, severe or long-standing deformities will not likely achieve true correction without surgery.
Surgical treatments are many and varied. They mainly involve the prevention of the abnormal middle joint extension. Some involve repositioning of the tendons on the side of the middle joint. If the middle joint is stiff or arthritic, the joint may be replaced or fused in a slightly bent position.
Postoperative and Rehabilitation Care
The hand should be immobilized in a plaster splint with the MCP joints in full extension and PIP joints flexed. Active flexion exercises should begin within the first 4 to 5 days if flexor tenosynovectomy has been performed. Dorsal extension blocking should be placed until 4 to 6 weeks postoperatively.
This video details how to use an Oval-8 Finger Splint for Swan Neck Deformity injuries.
- MedicalNewsToday. What's to know about swan neck deformity. Available from: https://www.medicalnewstoday.com/articles/318642.php (accessed 15 February 2019)
- Lane R, Nallamothu SV. Swan-Neck Deformity. InStatPearls [Internet] 2018 Sep 10. StatPearls Publishing.
- ASSH. Swan Neck Deformity. Available from: http://www.assh.org/handcare/hand-arm-conditions/swan-neck-deformity (accessed 15 February 2019)
- 3 Point Products. How to Treat Swan Neck Deformity with an Oval-8 Finger Splint. Available from: https://youtu.be/Dv_fTqEeFGQ