Symphalangism is a condition where there is congenital ankylosis [fusion] of the interphalangeal joints of the phalanges of the hand or foot.
The condition may involve metacarpophalangeal joints as well.
The condition occurs because of the failure of the interphalangeal joint to differentiate during the development.
Symphalangism leads to the functional impairment and unsightliness of the affected finger. Ulnar digits are more commonly involved.
The condition was first described by Harvey Cushing. The proximal interphalangeal joint is most commonly involved. It can be hereditary or nonhereditary.
It could be a hereditary or nonhereditary condition. Hereditary symphalangism is usually inherited as a dominant trait.
It is most frequently seen in Caucasians. It is less common in Orientals and even lesser in blacks.
Symphalangism can result in can be functional impairment in the grip and pinch actions of the affected hand as well as cosmetic issues.
The proximal interphalangeal joint of the hand is the most common site of involvement.
Causes, Pathophysiology and Grading of Symphlangism
Symphalangism occurs due to the failure of separation of the phalanges which then remain in fused condition. 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.
NOG gene or noggin gene has been related to the most cases of symphalangism. Mutations in GDF 5 [growth and differentiation factor 5] have also been associated.
An Attempt has been made to classify symphalangism based on radiographic appearance.
This classification is as follows
- Grade I or Fibrous – Mild joint space narrowing in the affected joint
- Grade II or Cartilaginous Symphalangism – Only a line of joint space is observed.
- Grade III or Bony Symphalangism- Visible bony ankylosis
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.
The congenital stiffness of the digits is the main presentation.
It could be spotted by the parents when the child attempts to grasp something. The patient would not make a fist properly. Older children have difficulty in difficulty picking up small objects.
On examination, there would be 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 x-rays are used to grade the symphalangism as marked by the narrowing of the interphalangeal joints. But as mentioned before, the age of the child needs to be considered too as the grade of the symphalangism may progress as the child grows older.
So it possible that one is not even able to detect the condition radiographically at birth because of a 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 needs to be individualized.
Very young children should not be operated. Most of the children have limited functional hampering and may not need surgery at all.
Soft tissue procedures provide maximum benefit when performed before 3 years of age. Arthrodesis and interphalangeal joint arthroplasty should only be considered after the skeletal maturity has been reached.
The various surgical options are
- Operative capsulectomy – It has limited success
- Angular osteotomy- For example, the digits that are fixed in extension will be functionally improved by flexion osteotomy.Rarely needed
- During adolescence only
Other procedures that may be required are correction In symbrachydactyly [ associated shortening of the fingers].
The digits may be needed to be lengthened 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.
- Takahashi T, Takahashi I, Komatsu M, et al. Mutations of the NOG gene in individuals with proximal symphalangism and multiple synostosis syndrome. Clin Genet. 2001;60(6):447–451.
- Baek GH, Lee HJ. Classification and surgical treatment of symphalangism in interphalangeal joints of the hand. Clin Orthop Surg. 2012;4(1):58-65. doi:10.4055/cios.2012.4.1.58. Link