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7. Ulnar Deficiency

Ulnar Longitudinal Deficiency

What is Ulnar Longitudinal Deficiency?
Ulnar Longitudinal Deficiency (ULD) is a lack of formation of the pinky side of the upper extremity. It usually affects the forearm but can affect the hand, forearm, and upper arm. It can affect bone, muscle, tendon, nerves, and blood vessels. The severity is different in each affected child.

What specific abnormalities are seen?
Hand: The entire hand may be affected. The thumb can be affected and the webspace between the thumb and the index finger is often narrowed. The hand can have syndactyly between other digits. In more severe cases, a variable number of digits may be absent. There can abnormal bony connections between the bones of the wrist and/ or bones of the hand (typically, the metacarpals).
Forearm: The ulna is most commonly short. It can be absent. The radius bone may be affected as well but usually is normal. Sometimes the radius is fused to the humerus (radioulnar synostosis).

What are other names for ULD?
The most common other name is ulnar clubhand. It is also sometimes called ulnar deficiency for short.

How does ULD happen?
The arm forms between 4 and 8 weeks of gestation, sometimes before a mom even knows she is pregnant. By 8 weeks the arm is fully formed although obviously really small. If there is some insult to the developing arm, part of it may not form normally. There are different types of insults- some are genetic and some may be caused by outside influences (“environmental factors”).

Are there medical problems associated with ULD?
The short answer is no. The only associated medical abnormalities are to the musculoskeletal system. Specifically, there can be abnormal development of the fibula (at the ankle) or even more rarely other bones in the lower extremity.