Symphalangism – Causes, Classification and Treatment

Symphalangism is congenital stiffness of the digits which occur due to the fusion of the joints of the fingers or toes leading to functional impairment and unsightliness of the affected finger. The condition was first described by Harvey Cushing. The proximal interphalangeal joint is most commonly involved. It can be hereditary or nonhereditary and the association has been found with syndromes like Apert and Poland.

Symphalangism occurs due to the failure of separation of the phalanges and results in the fusion of one phalanx to another within the same digit. It may occur as a simply isolated malformation or it may be associated with other deformities of the hands or feet, and it may also occur in numerous congenital syndromes such as Apert’s, Poland and Mobius syndrome.

When hereditary, symphalangism is usually inherited as a dominant trait.

It is most frequently found in Caucasians, occasionally in Orientals, and hardly ever in blacks.

Grades of Symphalansim

An Attempt has been made to classify symphalangism based on radiographic appearance.

This classification is as follows

Grade I or Fibrous Symphalangism

is present when there is mild joint space narrowing in the affected joint

Grade II or Cartilaginous Symphalangism

Only a slit of joint space is observed.

Grade III or Bony Symphalangism

There is bony ankylosis visible

In a very young child, over the involved joint,  volar skin crease may be absent or faint. Joint capsule and ligaments may be tight, allowing minimum motion of the affected joint. As the joint grows, it may fuse.

Thus, the same joint can be classified as fibrous, cartilaginous, or bony symphalangism according to the child’s age at diagnosis.

Presentation of Symphalangism

The congenital stiffness of the digits is the main presentation.

The disorder is characterized by a lack of motion of the affected joint in the finger. The skin overlying the fused articulation is smooth, and the transverse skin creases are absent.

This condition can be easily detected at birth.

Usually, more than one finger is affected. When the proximal interphalangeal joint is affected, the digit is usually fixed in extension. At the level of the fused joint, the soft tissues are narrowed.

The patient cannot make a fist and has difficulty picking up small objects.

Imaging

The x-ray may reveal any of the above-mentioned grades of symphalangism, depending on the age of the child. One cannot detect it radiographically at birth because of lack of ossification of the phalanges around the affected joint. With growth and maturation, when the bones ossify, there is a decrease in the joint width with eventual fusion.

Treatment of Symphalangism

Treatment is individualized.

The digits that are fixed in extension will be functionally improved by flexion osteotomy.

In symbrachydactyly, when there is an associated shortening of the fingers, one may gain relative length by recessing the interdigital webs into the spaces between the metacarpal heads.

Also, one may lengthen digits surgically.

Recent reports have suggested that the early release of the fusion when it is in fibrous stage may restore some motion. The child should be operated for this as early as possible.

The management of symphalangism with associated anomalies is complex. One should individualize the care; often it is difficult to improve function.

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