Amniotic Band Syndrome (ABS)

What is Amniotic Band Syndrome?

Amniotic Band Syndrome (ABS) is a congenital condition caused by fibrous bands from the amniotic sac entangling fetal limbs or other body parts, leading to deformities or amputations. The incidence is estimated at 1 in 1,200 to 15,000 live births.

Causes

The exact cause of ABS is unclear, but the most accepted theory is the extrinsic theory, which suggests early rupture of the amnion without damage to the chorion. This results in fibrous strands that encircle and constrict fetal parts, disrupting normal development.

Clinical Features

• Limb constriction bands causing distal swelling
• Intrauterine amputations leading to missing fingers, toes, or limbs
• Syndactyly or fused digits due to abnormal tissue connections
• Clubfoot and joint contractures due to restricted movement
• Craniofacial abnormalities, including cleft lip/palate and asymmetric facial development in severe cases

Associated Conditions

• Vascular disruption leading to limb ischemia and necrosis
• Neuromuscular deficits if nerves are affected
• Amputation-like limb deficiencies, which may require prosthetic fitting and rehabilitation

Evaluation and Diagnosis

ABS is diagnosed clinically based on characteristic deformities and imaging studies like prenatal ultrasound or postnatal X-rays to assess bone involvement. Treatment depends on severity, ranging from observation to surgical interventions for functional improvement.

References

1. Poeuf B, Samson P, Mary P. Amniotic Band Syndrome: A Review. Orthop Traumatol Surg Res. 2008;94(5): 450-454.
2. Goldfarb CA, et al. Congenital Hand Differences: Principles and Management. J Hand Surg Am. 2009;34(7):1351-1359.
3. Martínez-Frías ML. Epidemiological characteristics of amniotic band sequence. Am J Med Genet. 1997;73(1):81-86.