This is the second of my series of blog posts in response to questions presented to me at the 2014 Williams Syndrome Association National Convention. See Q1 here.
Q2: Is Radio-ulnar synostosis related to WS?
One of the clinical symptoms related to WS is radio-ulnar synostosis or an issue where the radius and ulna are fused in a person's lower arm(s). A typical forearm is designed in a way to allow the hand to maneuver in a variety of ways in order to manipulate objects in the hand. When you extend your arm out with the palm facing downward (pronation) and then twist your palm to face upwards (supination), the bones in the lower arm direct that motion.
In the pictures above, the radius is highlighted on the left drawing and the ulna is highlighted in the right drawing.
The lower arm is made up of two bones, the ulna and the radius. The ulna is the bone that makes up the elbow. Touch your elbow, you are touching a large protrusion on the superior portion of the ulna, called the trochlea. The ulna also articulates or creates a joint at the outer most edge of the wrist but in a much less pronounced way. The second bone of the lower arm is the radius. The radius articulates or connects to the majority of the bones in the wrist and extends to the elbow where it ends with a small concave circular notch that allows it to turn. The radius is named for this motion. Place your hand on your ulna (elbow) and follow that bone down the outside of your arm. Now twist your palm up and down and notice that bone moves very little. The other bone, the radius, moves quite a lot! The radius is on the inside of the arm and it rotates around the ulna. Watch this short youtube video to see an "insider's" view of how these bones twist the hand.
Now, imagine the radius and ulna bones are connected. Would you still be able to twist your palm up and down? No! This is what happens during radial-ulnar synostosis or the fusion of the radius and ulna. It affects 26% of individuals with WS. My daughter has this in her right arm and it restricts the amount of motion and actions she can do with her right hand.
In the photos above, the left is an x-ray view of a typical bone arrangement in the elbow. This is in supination position (palm rotated upwards). The photo on the right is one of an individual with radial-ulnar synostosis. Their radius and ulna are fused at the elbow making it impossible for them to rotate their lower arm.
If your child has radial-ulnar synostosis, there isn't much you can do, medically, to treat it. Even if the bones were surgically separated, they will not have the same bone structure, vascular supply and ligament/muscle attachment that would allow the bones to rotate properly. You would be hard pressed to find a surgeon to do this type of treatment unless the fusion very severely limits any use of the arm.
The best way to handle this condition is to modify surroundings and teach the affected individual adaptations they can use to manipulate objects. You may often find that they have a harder time manipulating small objects and holding writing utensils, such as pencils and crayons. My daughter shows preference in her left hand for writing but that wasn't always the case. She often manipulates items with her right and then will switch to the left. This may be her way of adapting to her environment since she has more movement in the left than her fused right arm. Many find that being ambidextrous out of necessity is the case for those with radial-ulnar synostosis. Other actions that may be difficult if they have a fused arm includes:
The best way to handle this condition is to modify surroundings and teach the affected individual adaptations they can use to manipulate objects. You may often find that they have a harder time manipulating small objects and holding writing utensils, such as pencils and crayons. My daughter shows preference in her left hand for writing but that wasn't always the case. She often manipulates items with her right and then will switch to the left. This may be her way of adapting to her environment since she has more movement in the left than her fused right arm. Many find that being ambidextrous out of necessity is the case for those with radial-ulnar synostosis. Other actions that may be difficult if they have a fused arm includes:
- holding spoons/forks during feeding
- manipulating buttons, belts and zippers
- sports that require wrist rotation such as catching a ball
- turning a doorknob
- handwriting
- manipulating coins and other small objects
- pouring liquids
- playing instruments such as guitar that requires wrist manipulation
Coupled with the visuospatial issues and motor control that individuals with WS have, the tasks listed above can be even more difficult. You will find that if your child has radioulnar synostosis, they will adapt on their own but there are many ways you can help. For example, you can chose clothing that doesn't require buttons or replace knobs on doors with handles. There are also many adaptive technology apps that are available to help your child with academics and self help skills. This was a major topic of interest at the convention. To access the WSA's list of useful apps visit the website here.
If you have specific ways you have helped your loved one or students adapt to radioulnar synostosis, I'd love for you to share. Please feel free to leave your experiences with this in the comments section of the blog or on the WS support group thread!
Source:
Radio- ulnar synostosis and its occurance in WS; 1991 *Note this was published prior to the use of FISH testing for WS diagnosis so information is clinical.
