Swan neck deformity refers to a deformity of the hand or foot. It affects the tendons and therefore the individual joints.
In the hand, the proximal and distal interphalangeal joints (middle and end finger joints) are affected. In swan neck deformity, the middle joint of the finger is hyperextended and the end joint of the finger is flexed at the same time. The metacarpophalangeal joint of the finger also often remains in a flexed position.
The swan neck deformity of the foot leads to the so-called claw position or claw toe due to the flexed position of the toe joint.
The deformity of the fingers is caused by a defect in the finger and flexor tendons in the area of the middle joint. The cause is often an accident or trauma that leads to a tear in the palmar tendon plate. The palmar tendon plate is located at the metacarpophalangeal joint.
As a result, normal joint function is no longer possible.
A swan neck deformity on the fingers also tends to occur in patients with rheumatoid arthritis. This chronic systemic disease affects the inner lining of the joints and causes inflammation there.
The swan neck deformity is primarily caused by destruction of the joint and a resulting flexor tendon injury. Caking of the flexor tendons due to inflammation is also a possible cause of swan neck deformity.
The main cause of the deformity of the toes is mechanical stress.
Overview of the bones of the hand © bilderzwerg / Fotolia
The early signs of deformity include
- Pain when bending the fingers and
- a slight, often only slightly noticeable bending of the finger joints in the wrong direction.
At an advanced stage, the typical appearance of swan neck deformity is easy to recognize.
In stages I and II, the deformity can still be corrected actively or passively with splints. In the third stage, the deformity is fixed. Patients can then no longer clench their hand into a fist and the pincer grip is also impaired. This significantly restricts them in their everyday life.
Many patients also perceive the deformity as a cosmetic blemish and feel extremely uncomfortable with it.
Swan neck deformity of the fingers in connection with rheumatoid arthritis © bilderzwerg / Fotolia
The deformity of the fingers or toes is quite noticeable, especially at an advanced stage. The doctor can therefore quickly make a suspected diagnosis. In a detailed consultation, he or she will also determine the possible causes of the swan neck deformity.
The doctor then examines the hands and feet for swelling. Checking joint and visual function is also part of the physical examination.
An X-ray or MRI examination and a blood count can provide further indications of the underlying disease. In the case of rheumatoid arthritis, for example, the blood count will show a positive rheumatoid factor (RF).
The type of treatment depends primarily on the cause of the deformity.
If the swan neck deformity is due to an injury, treatment by a trauma surgeon may be necessary. In this case, the trauma surgeon corrects the tendon injury using tendon sutures . Such tendon sutures can be performed up to 14 days after the actual trauma.
In the case of more recent injuries, however, the doctor performs a so-called tendonplasty (tendon replacement surgery). The doctor replaces or stabilizes the damaged tendon with the body's own (autologous) or artificial tendon replacement material.
In the case of a mild deformity caused by a rheumatic disease, the orthopaedist or rheumatologist prescribes a flexor splint and physiotherapy for conservative treatment. More serious grade II or III deformities, on the other hand, require surgical intervention.
Various surgical interventions are possible here. For example, the doctor can remove the synovial membrane in the affected joint (synovectomy) or loosen adhesions in the area of the flexor tendons. Tendon reconstruction or artificial joint replacement are also possible surgical procedures.
In cases of advanced joint destruction, arthrodesis, i.e. surgical stiffening of the joint, is the therapeutic method of choice.
