Ulnar Deficiency

Ulnar Longitudinal Deficiency: The Basics

What is Ulnar Longitudinal Deficiency (dysplasia)?
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 are 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.  


  1. First off, I am so very thankful to have found this blog. Our son is 5 months old, we learned at our 18 week scan that he would have an absent fib/shortened femur on the right, malpositioned left foot (layed against shin) and an absent pinky finger on the right hand. When he was born we learned more. In total, his issues are 1) R Absent fib/shortened femur, missing pinky toe 2) L caling FH bilateral because of dynamic valgus ankle and tib measures 72% of femur 3) Ulnar defiency in right with radial head dislocation, elbow contracture of 20%, missing pinky finger, hypoplastic thumb and first finger 4) Ulnar defiency in left, less prominent radial head dislocation but 20% elbow contracture and slightly hypoplastic thumb and first finger. So we have good resources for the lower extremities but there's not a lot of info for the upper. He has a 3mm lld between r and l arm. Right ulna meausure 65mm (1mm shorter than radius) and left ulna measures 68mm. We understand that he's on the milder spectrum for all these issues. His arms are shorther than another child his same age, but he's very functional and not dirastic. It was suggested at a consult on his legs that we lengthen the ulnas to reduce the radial head dislocation. What are your thoughts on that? Also, is there anyway to tell me what a child without ulnar defiency ulna length should measure at 5 months. I guess I'm trying to understand more how far off from average he is. I'm so, so happy to find this site to learn more about his issues and what other parents have asked and had answered. Sorry for the very long comment but thank you in advance for your feedback. Melanie from Michigan

  2. Melanie- I responded to part II first- sorry for confusion. Unfortunately, while there are average ulna lengths, those data are just not that helpful in these situations for a number of reasons. Feel free to contact me off line if I can answer other specific questions. Again, sorry to be vague in my responses.

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