Causes / typical injury mechanism: Radial clubhand, also known as radial deficiency or radial dysplasia, is usually congenital. The etiology is uncertain but thought to be due to fibroblast growth factor deficiency due to issues with sonic hedgehog genes. Birth defects can be inherited, sporadic, or environmental.

Classic history and presentation: Classically, an infant presents with an abnormal or absent thumb and a radially angulated hand. This is bilateral in about half of cases; if unilateral, the defect is more likely to be on the right side.

Prevalence:

• Sex / gender – 3:2 male-to-female ratio

Risk factors:

• Genetic abnormalities (can be sporadic)
• Drug exposure (such as thalidomide)
• Intrauterine compression

Pathophysiology: The disruption of radioulnar growth in varying degrees leads to mild-to-severe deficits.

Grade / classification system: Bayne and Klug –

• Type 1: mild hypoplasia of radius, growth plate present
• Type 2: hypoplastic radius, no growth plate
• Type 3: partial absence of radius
• Type 4: complete absence of radius