What causes ulnar club hand?
Ulnar club hand is a birth defect. As with the majority of birth defects, researchers do not know why it occurs, but information that is known about ulnar club hand indicates that it doesn’t result from anything the mother did (or didn’t do) during her pregnancy.
Ulnar club hand develops early in pregnancy — sometime between the 28th and 56th day of gestation — when the bones of the hand and forearm are being formed.
It is sometimes, but not always, picked up on a prenatal ultrasound.
Even if it is detected prenatally, the condition cannot be treated until after your baby is born.
How common is ulnar club hand?
It’s less common than radial club hand. It’s present in about 1 in 100,000 babies.
How is this going to affect my child?
It really depends on the severity of the problem.
In the mildest cases, the ulna is merely slightly smaller than normal and there is minimal deviation at the wrist. This won’t cause many problems in your child’s development.
This is the most common form of ulnar club hand. It involves a partial absence of the ulna and the hand appears deviated toward the ulnar side. Bowing of the radius may also occur.
Your child’s ulna is completely absent, leading to limited range of motion at the wrist.
- The elbow joint may also be disturbed or even fused with no motion.
- There may also be underdevelopment or absence of the thumb, which interferes with hand function.
Here, there’s an abnormal connection between your child’s radius and humerus, resulting in bowing of the radius and hand deformations.
A tethered wrist?
The severity of ulnar club hand is also affected by the presence of an abnormal bar of fibrous tissue that may appear when the part of the ulna near the hand is absent. This fibrous tissue has a very limited ability to grow. It is attached to the ulnar side of the hand and wrist.
As the radius grows in the mothers' womb, the lack of growth in the ulnar side draws the hand into a deviated "club" position.
What other symptoms might my child have?
The most severe cases lead to significant problems in the function of the hand, fingers and elbow.
- Your child’s entire arm will be shorter, with curving of her forearm and stiffness of her elbow and fingers.
- Your child’s thumb will either be very small or missing.
The arrangement of muscles and nerves may be unbalanced and some muscles and nerves may even be absent.