KEY FACTS
Terminology
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Spectrum of anomalies, including absence or hypoplasia of radius, radial carpal bones, &/or thumb
Imaging
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Single forearm bone
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Radial deviation of hand
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Fixed on prolonged scanning, not positional
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Abnormal thumbs: Use cine clips, 2D and 3D imaging
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Absent or hypoplastic
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Proximal implantation
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Adducted (rolled onto palm)
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Triphalangeal (normal thumb has only 2 phalanges)
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Scanning Tips
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Distinguish from arthrogryposis, which also has abnormal hand position
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Global lack of fetal movement
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Abnormal positioning of hands and feet
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All bones and digits present in arthrogryposis
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Look for other findings: 86% of patients with hypoplastic thumbs have other anomalies
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Multiple anomalies increase likelihood of aneuploidy/syndrome
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44% have either Holt-Oram or VACTERL association
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Obtain formal fetal echocardiogram in all cases
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Atrial septal defect is most common abnormality in Holt-Oram; very difficult fetal diagnosis
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Monitor for fetal growth restriction
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Aneuploidy, especially trisomy 18
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Cornelia de Lange syndrome (diaphragmatic hernia, abnormal facies)
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Fanconi anemia (severe growth restriction, abnormal thumbs/eyes/kidneys)
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Use 3D US for facial detail/thumb morphology
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May lead to specific syndromal diagnosis (e.g., Cornelia de Lange syndrome)
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, malpositioned, hypoplastic, or triphalangeal. The hand position is often abnormal 
. The hand is deviated toward the side of the radius, which is either absent 
or hypoplastic. The condition is also known as radial clubhand and radial dysplasia.
