What is swan neck deformity?
Swan neck deformity is a permanent joint disorder that occurs in finger(s). In such case the uppermost joint of the finger that is nearer to the finger tip is bent inward whereas the joint present at the base of the finger is deformed and bent out ward and produce distance from palm.
The two joints of finger which deformed in swan neck deformity are proximal interphalangeal (PIP) joints and distal interphalangeal joints (DIP).
- Proximal interphalangeal (PIP) joints are present at the base of the finger.
- Distal interphalangeal (DIP) joints are present at the end of finger.
Anatomically, bending of the Proximal interphalangeal (PIP) joint is termed as hyperextension and distal interphalangeal (DIP) joints deformity is termed as flexion. Both these deformity is linked with each other and can result in any part either at PIP or at DIP.
The hyperextension of PIP occurs due to rapture of the major ligaments of the palm known as volar plate. Volar plate is a thick ligament which controls the extension and prevents hyperextension. While any blunt force which causes injury in extensor digitorum tendon at the distal interphalangeal joint (DIP) of the fingers is the origin of hyperflexion.
Combination of mallet deformity with extensor digitorum tendon rapture leads to hyperextension in PIP which causes swan neck deformity.
In general, swan neck deformity can be explained in following ways:
- extension of the volar plate at PIP joint causes permanent constriction;
- abnormal contraction of collateral ligament
- DIP lacks its rigor.
Causes of Swan neck deformity
Different degenerative joint disorders which cause swan neck deformity are:
- rheumatoid arthritis
- Without proper medical treatment for mallet finger
- At the finger ligament, formation of fibrous plate at the base of the fingers,
- chronic muscle spasticity which lead to nerve damage at the hand
- psoriatic arthritis
- cerebral palsy
- Parkinson’s disease
- Tearing of finger ligament, and
- Facture of the PIP joints in the middle bone of the finger causing misalignment and not cure properly
Inflammatory diseases like rheumatoid arthritis or other injury causes pain and tenderness in the PIP joint. This may lead to extensive bending and causes hyperextension to PIP joint. Eventually deformed DIP joint and downward bending leads to hyper-flexion. Both these bending cause imbalance between the adjoining ligaments and results to a typical shaped finger which is termed as swan neck deformity.
Physical examination is the prime diagnostic approach for swan neck deformity. Sometimes physician also recommended conducting X-ray to examine the condition related to the alignment of joint, ligament tearing or analysis of the joint surface and also to check any traumatic injury which may causes finger fracture. Usually no other test is conducted for swan neck deformity.
Swan neck deformity can be treated by nonsurgical and surgical procedures. Doctors take the decision for treating swan neck deformity depending upon the flexibility and stiffness of the PIP joint.
The approach of nonsurgical treatment is the restoration of balance in the structures of the fingers and palm. In treatment, the target is to fixation of correct alignment and reduction of stiffness of the PIP joint which avert hyperextension. Prevention of hyperextension assists to repair DIP extension.
Skilled and experienced physiotherapist consultation with proper infrastructure healthcare system helps to proper rehabilitation. The different techniques which include in physical therapy are
- Stretching exercise
- joint mobilization
These may allow maintaining the balance.
To maintain the proper elasticity in the PIP joint, application of a device which is shaped like jewellery ring and made with gold, sterling silver or stainless steel is the newer approach. Extension obstructing splint and similar type of approaches are usually provide authentic results may gives relaxation from inflammation but unable to balancing the ligaments attached with PIP.
However, many hand surgeons will try six weeks with the splint and exercise to improve PIP joint mobility before performing surgery.
Various surgical approaches can help to maintain the elasticity and repair the adjoining tissue to modify the swan neck deformity.
Adjoining Tissue restoration
Surgery in the adjoining tissues helps to repair or rearrange them in such a way that imbalance or deformity will be resolved. Adjoining soft tissues surrounded with PIP are skin, tendons and ligaments. The surgical procedures which can reconstruct or repair adjoining soft tissues are:
- Dermadesis: This surgical procedure is based on the concept of producing a skin scarcity to the palm of the hand for prevention of the hyperextension in PIP.
- Tenodesis: In this surgery, the holding of tendon is reconstructed.
- Mobilization: Surgical correction of immobility of PIP or DIP joint.
Arthroplasty in PIP Joint
In arthroplasty, the replacement of rigid PIP is performed to regulate the Swan neck deformity.
Finger Joint Fusion
Finger Joint fusion is a surgical procedure that attaches the two planes of the finger joint, and maintains their movement. Combining the two joint planes together removes pain, the joint becomes stable, and assists to put off added joint abnormality. This type of surgical process is mainly applied when rheumatoid arthritis causes the PIP joint supply due to mallet deformation of the DIP joint.
Image 1 – Swan neck deformity anatomy
Image 2 – Swan neck deformity picture
Source – images.rheumatology.org/
Image 3 – Splint for Swan neck
Source – ncmedical.com