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Syndactyly (Fused Fingers)

Syndactyly (Fused Fingers)

Syndactyly is a congenital condition in which two or more fingers are fused together, either by skin, soft tissue, or bone. It is one of the most common congenital anomalies of the hand, occurring in approximately 1 in every 2,000–3,000 live births. Syndactyly can affect one or both hands, and while it may appear as an isolated anomaly, it is sometimes associated with genetic syndromes or other limb abnormalities.

The condition not only impacts the appearance of the hand but can also interfere with normal growth and function. Because the hand plays such a critical role in grasping, holding, and fine motor skills, syndactyly can significantly affect a child’s development and quality of life if not treated appropriately.

Anatomy and Development

During normal embryonic development, the fingers form as separate structures around the 6th to 8th week of pregnancy. Initially, the hand is shaped like a paddle, and the fingers gradually separate through a process known as apoptosis (programmed cell death). Syndactyly occurs when this process is incomplete, leading to persistence of webbing or fusion between digits.

The condition most commonly affects the middle and ring fingers, but any fingers can be involved. It may occur unilaterally (one hand) or bilaterally (both hands).

Pediatric Hand Problems

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Causes and Risk Factors

Syndactyly develops during fetal growth when the fingers, which normally separate by a process called apoptosis (programmed cell death), fail to divide fully. This failure results in persistent fusion of adjacent digits. The exact cause is not always known, but several factors contribute:

  • Genetic Influence – Syndactyly can be inherited in families, often following an autosomal dominant pattern. Mutations in certain genes that regulate limb development, such as HOX genes, play a role.
  • Sporadic Cases – Many instances occur without a family history and are considered isolated.
  • Syndromic Associations – Syndactyly is sometimes part of syndromes such as Apert syndrome, Poland syndrome, or Carpenter syndrome. In such cases, it may be accompanied by craniofacial, cardiac, or skeletal anomalies.
  • Environmental Factors – Less commonly, external influences during pregnancy, such as exposure to harmful substances or maternal illnesses, may contribute to abnormal hand development.

Types of Syndactyly

  • Simple Syndactyly – Fusion involves only soft tissues like skin and connective tissue, without bone connection. This is the most common form.
  • Complex Syndactyly – Fusion extends deeper, involving bones, tendons, or nails. In these cases, the fingers may share joints or bone segments.
  • Complete Syndactyly – The fingers are fused along their entire length up to the fingertips.
  • Incomplete Syndactyly – Fusion occurs only along part of the finger length, with the tips remaining separate.
  • Complicated Syndactyly – Associated with abnormal bones or digits, such as extra fingers (polydactyly) or twisted bone formations (synostosis).

Clinical Features

  • Visible webbing or fusion between fingers.
  • Limited range of motion in affected fingers, especially in complex cases involving bones or joints.
  • Differences in finger length or shape if abnormal growth occurs.
  • Functional difficulties with fine motor tasks, grip, or dexterity, particularly when multiple digits are involved.
  • Cosmetic concerns, which may affect self-esteem in older children and adults.

Diagnosis

  • X-rays – To determine whether bones, joints, or tendons are involved.
  • Genetic testing – If syndactyly is suspected to be part of a syndrome, genetic evaluation may be recommended.
  • Functional assessment – To evaluate how the fusion impacts grip, finger mobility, and hand function.

Treatment

1. Timing of Surgery –

  • Surgery is typically performed between 12–24 months of age. Early intervention prevents abnormal growth patterns, especially if the fusion involves fingers of unequal length.
  • In severe cases affecting thumb-index or ring-little finger fusion, surgery may be prioritized earlier because these pairs are crucial for grip and hand function.

2. Surgical Techniques –

  • Skin Flaps and Grafts – After separating the fingers, surgeons use local skin flaps or skin grafts (often from the groin or inner arm) to cover the exposed areas.
  • Z-plasty or Geometric Flaps – Techniques designed to minimize scarring and contracture while providing adequate skin coverage.
  • Bone and Tendon Correction – In complex syndactyly, additional procedures may be required to realign bones or separate tendons.

3. Postoperative Care –

  • Splints or casts are applied to protect the separated fingers during healing.
  • Physical or occupational therapy helps restore movement, strength, and coordination.

Prognosis

With timely and appropriate surgical treatment, most children achieve good functional and cosmetic outcomes. Simple syndactyly generally has excellent results, while complex cases may require multiple surgeries and may still leave some limitations in motion or appearance. Scarring, recurrence of webbing (known as “web creep”), and differences in finger length or nail appearance are potential complications.

Psychosocial Considerations

Beyond physical function, syndactyly can affect a child’s confidence and social interactions. Visible hand differences may draw unwanted attention, especially in school-aged children. Counseling and supportive care, alongside surgery, can help improve emotional well-being.

Conclusion

Syndactyly, or fused fingers, is a relatively common congenital hand anomaly that ranges from simple soft tissue connections to complex bone fusions. While the condition may seem primarily cosmetic in mild forms, it can significantly impact hand function when multiple or complex fusions occur. Early diagnosis and timely surgical intervention are key to achieving the best outcomes. Advances in surgical techniques have made it possible for most children with syndactyly to lead normal, active lives with good hand function and appearance.

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