Radial aplasia is a

congenital defect A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can r ...

which affects the formation of the

radius bone The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is usually slightly longer tha ...

in the arm. The radius is the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

bone (thumb side) which connects the humerus of the upper arm to the wrist via articulation with the carpal bones. A child born with this condition has either a short or absent radius bone in one or both of his or her arms. Radial aplasia also results in the thumb being either partly formed or completely absent from the hand, which can result in difficulties performing

activities of daily living Activity may refer to: * Action (philosophy), in general * Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may s ...

. Radial aplasia is connected with the condition

VACTERL association The VACTERL association (also VATER association, and less accurately VACTERL syndrome) refers to a recognized group of birth defects which tend to co-occur (see below). This pattern is a recognized association, as opposed to a syndrome, because th ...

, under the 'L' for limb malformations. Radial aplasia is not inherited. The cause for radial aplasia is unknown, but it widely believed to occur within the first ten weeks of gestation. The incidence is reported to be between 1 in 30,000 and 1 in 100,000 live births, bilateral in half, slightly more common in boys than girls. Most cases are sporadic, with only about 20% familial.

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Skeletal disorders {{congenital-malformation-stub