Introduction
Symbrachydactyly is a rare, non-hereditary condition affecting both sexes. It is prevalent in 1 out of 32000 babies. Usually, one side of the body is affected. In the place of fingers, there can be a small, stunted bump (nubbins) containing elements like nail plate, cartilage, and bone. Symbrachydactyly may be associated with 'Poland Syndrome'. Poland Syndrome is a condition wherein there are underdeveloped or missing muscles on one side of the body, especially the primary muscle of the chest called 'pectoralis major.' These individuals have unilateral (one side) chest, shoulder, hand, and arm abnormalities.
What Are the Causes of Symbrachydactyly?
The exact cause is unknown, and no specific genes have been known to cause the condition. However, the subclavian artery is a blood vessel that supplies blood mostly to the arms, neck, and chest. During fetal development, around the sixth week, there might be a disturbance in the blood vessels that forms the subclavian arteries (subclavian artery supply disruption sequence). This leads to failure in the development of the upper limbs and fingers.
The cells present at the distal (far end) of the limb bud in the fetus are responsible for early limb development. These cells are called the 'apical ectodermal ridge.' Disruption in the formation of the apical ectodermal ridge also contributes to symbrachydactyly. There can be a regeneration of certain distal (far end) limb buds following damage to the apical ectodermal ridge, which results in underdeveloped fingers or small, stunted bumps called nubbins.
How Can Symbrachydactyly Be Diagnosed?
Symbrachydactyly can be diagnosed before birth using ultrasound. If the doctors diagnose the condition after birth, X-rays might be taken to check the bones that are joined to decide the mode of the treatment.
Symbrachydactyly might mimic another condition called amniotic band syndrome (ABS). In amniotic band syndrome, a strand of amniotic tissue limits the external growth of the finger, toe, or limb. Symbrachydactyly affects the inner parts of the hand, like nerves, bones, and muscles.
What Are the Types of Symbrachydactyly?
Based on the appearance, symbrachydactyly can be classified as
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Short Finger Symbrachydactyly: This is the most common and less severe type. The thumbs appear and function normally, but the other fingers might be short and webbed.
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Bidactylous Symbrachydactyly: The thumbs and little fingers appear normal, but the other fingers might lack proper function and development.
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Monodactylous Symbrachydactyly: Only the thumbs appear to be properly developed and functional.
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Adactylous or Peromelic Symbrachydactyly: This is the most severe form wherein all the fingers may be partially developed (stunted or underdeveloped) or non-developed. These individuals might also have difficulty moving their wrists.
Based on the severity, symbrachydactyly can be classified as
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Mild Symbrachydactyly: The fingers are slightly short and movable with considerable webbing. The hand, a few finger bones, and the thumb are present.
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Moderate Symbrachydactyly: The finger bones are completely absent or partially present. The missing area can have minimal growth or projection of skin or soft tissue.
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Severe Symbrachydactyly: The fingers are absent, and the thumb may be partially or completely absent.
What Are the Clinical Manifestations of Symbrachydactyly?
The following are the clinical manifestations of symbrachydactyly:
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The hands and fingers appear short due to short bones.
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The fingers look like they are joined together (webbed) and can be stiff. This webbed appearance is called syndactyly.
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The bones in the fingers and hand can be completely absent.
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The presence of small thumbs is called thumb hypoplasia, while thumb aplasia denotes missing thumbs.
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Fingers might be replaced by small, stunted bumps of skin or tissue called nubbins.
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It usually affects only one hand.
What Are the Treatments for Symbrachydactyly?
The main aim of the treatment is to normalize the hand's appearance and function and enable the child to understand certain limitations. Treatment is based on clinical, radiological (X-ray) findings and the severity of the condition. Surgery might be required in severe cases. Non-surgical treatment modes include:
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Use of artificial limbs or body parts (prosthetics).
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Support by a physical therapist (these therapists help improve hand movement and function).
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Support by an occupational therapist (these therapists help individuals carry out day-to-day activities easily and focus on improving fine motor skills).
What Does Symbrachydactyly Surgery Include?
Symbrachydactyly surgery for severe cases includes:
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The surgery is performed in an operation theater by administering general anesthesia (sedating the child). Cuts are made in the area and stitched together after the surgery.
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The child should not be sick during surgery.
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The surgery targets to remove finger webbing and loose knuckle joints to allow the fingers to move freely. This helps the child to hold an object with ease.
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One or more bones or multiple toes might be transplanted from the toe to the affected hand through a process called toe transfer or toe-to-hand transfer to lengthen the fingers.
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After the surgery, the child might require a cast above the elbow to prevent it from moving for at least three weeks. Once the cast is removed, a splint (a material that supports the broken bone and keeps it in place) is placed and slides between the fingers, keeping them separate. The child might require a splint for six weeks.
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The physical or occupational therapist will guide the child to prevent stiffness and swelling and enhance function.
Though the complications following surgery are minor, long-term complications include:
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Poor bone healing.
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Stiff knuckle joints.
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Infection.
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Finger dislocation.
How Will the Progress Be in a Child With Symbrachydactyly?
Surgery has been very successful in children with symbrachydactyly. Few children can notice a difference following the first surgery, but few may require further surgeries. They can learn to adapt to new movements with the help of physical or occupational therapists. As the child grows, artificial hands (prosthetics) might be required to carry out daily tasks and sports activities. Even with surgery, the hands and fingers might look different and psychological management is required to help the child accept the condition. Long-term follow-up is necessary to ensure proper healing and function and to assess if additional surgery is required to enhance the function or appearance.
Conclusion
Symbrachydactyly is a rare condition, and its treatment requires a multidimensional analysis. Careful clinical and radiological (X-ray) evaluation helps decide the appropriate treatment method to boost the child's quality of life. With various surgery options, the function and appearance of the affected part can be improved but not completely restored. The child might need psychological help to accept the condition. The parents must be educated about the surgery's outcome, after which an informed decision can be taken.
