The improperly formed ulna may cause the wrist to deviate toward the little finger. This may cause the radius to bow. There may be deformities in the fingers and thumbs as well.

In most forms of ulnar club hand - which can present itself in a wide range of severity - not only is the bone abnormal but the soft tissues and flesh of the forearm are also abnormal. The arrangement of muscles and nerves may be unbalanced and some muscles and nerves may even be absent. The condition is sometimes called "ulnar dysplasia" which simply means abnormal development of the ulna.

As with the majority of birth defects, scientists do not know why ulnar club hand occurs, but information that is known about the condition indicates that it does not result from the mother's lifestyle or anything the mother did during her pregnancy.

Type 1: This is the mildest form of ulnar club hand. Although the ulna is underdeveloped, both ends of the bone (epiphyses) are present. The growth plates at both the distal (hand side) and proximal (elbow side) are in tact, but growth is slowed. Deviation of the wrist and bowing of the radius is minimal. Sometimes there are other malformations of the hand.

Type II: 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. There is an abnormal bar of fibrous tissue, known as anlage, extending from the distal (wrist side) end of the partial ulna to the wrist. Bowing of the radius may also occur.

The presence of the ulna in Type 2 cases is usually sufficient enough that the elbow is functional and stable. There may be some degree of deformity in the fingers or thumb.

Type III: This type involves complete absence of the ulna. The elbow is unstable. Hand and wrist malformations are common.

Type IV: This type involves an abnormal connection between the humerus and radius (synostosis). There is an ulnar anlage present from the distal (hand side) humerus to the wrist, with considerable bowing of the radius and ulnar deviation of the hand. Hand anomalies are common.

• your child's age, overall health, and medical history
• the severity of the condition
• any other deformities or syndromes associated with the problem
• your child's tolerance for specific medications, procedures, or therapies
• your opinion or preference

In more severe cases, surgery is necessary. If your child's doctor recommends surgery, keep in mind that range of motion exercises are still extremely important. Even if wrist therapy alone doesn't resolve problems with the wrist, you should not be discouraged from continuing the exercise regimen. Remember that any improvement in range of motion achieved through exercise will make subsequent surgery more effective and perhaps less complex.

• Surgical excision of anlage to reduce or eliminate deviation of the hand.
• A procedure to correct the bowing radius called osteotomy, in which a surgeon cuts the radius into wedges and refits them into a straight position.
• Osteotomy of the humerus (upper arm bone) to better position the wrist and hand
• Repair of digital and thumb deformities, such as: