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.
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.
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
- manipulating coins and other small objects
- pouring liquids
- playing instruments such as guitar that requires wrist manipulation
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.