What is Radial Dysplasia?
Radial club hand is a name for a range of different birth defects that affect the side of the forearm where the thumb is. These conditions can range from a too-small thumb to a missing bone called the radius that’s normally part of your forearm. The condition might also mean that muscles, ligaments, tendons, nerves, and blood vessels on that side of the arm haven’t fully developed. Radial club hand is also known by other names, such as radial dysplasia, radial longitudinal deficiency, and radial ray deficiency.
The first recorded case of radial club hand was described by Jean-Louis Petit in 1733, when he documented a newborn boy who had no radius bone in either arm. The first comprehensive study of this condition was done by a researcher named Kato in 1923, when he reviewed 250 cases of radial club hand.
What Causes Radial Dysplasia?
The exact genetic reason for radial dysplasia, a condition that affects the development of the forearm, is still not known. However, experts believe it could be due to a decrease in the functioning of something called ‘fibroblast growth factor’. This decrease might happen because of changes in a gene known as ‘sonic hedgehog’.
There have been several possible reasons suggested for what’s known as ‘radial club hand’, a deformity of the hand and forearm. These include problems with blood supply, compression while the baby is still in the womb, environmental factors, exposure to certain drugs before birth, and genetic reasons.
Risk Factors and Frequency for Radial Dysplasia
Radial dysplasia is a rare condition that happens to be the most common type of congenital longitudinal deficiency. This means it is a defect that kids are born with, affecting the growth of their arms. It occurs more often in boys than girls, with about 3 boys affected for every 2 girls. Radial dysplasia is estimated to happen in about 1 out of every 55,000 births. However, a study from Finland suggests it might be more common there, affecting nearly 1 in every 5,000 live births.
Signs and Symptoms of Radial Dysplasia
Radial dysplasia is a condition in children that causes unusual development in the thumb and forearm. The presentation and severity of this condition can vary greatly. Some common signs include a hand that turns outward at an angle to the forearm, and a thumb that is either underdeveloped or missing. Not only bones are affected by this condition, but also muscles, tendons, nerves, and joints. In most cases, the arm bone on the side of the little finger (the ulna) is shorter and curved in line with the level of radial deficiency. It’s important to note that these abnormalities often occur in both arms and an in-depth examination of both upper limbs is recommended if radial dysplasia is suspected in one.
- Hand turns outward at an angle to the forearm
- Underdeveloped or missing thumb
- Affected muscles, tendons, nerves, and joints
- Shortened and curved ulna
- Potential bilateral occurrence
Testing for Radial Dysplasia
In medical terms, radial club hand refers to a deformity of the arm characterized by the underdevelopment or absence of the radius bone (one of the two main bones in the forearm). This condition can be observed through medical imaging (like X-rays), and can range in severity. It has been classified into four types by Bayne and Klug in 1987.
Type I radial club hand is characterized by a shortened distal radius bone (the end of the radius bone closest to the wrist is present, but it’s shorter than normal).
In Type II, the radius bone is considerably smaller and thinner compared to the other forearm bone, the ulna, and there’s no growth plate (an area of growing tissue near the ends of long bones in children and adolescents) present at the end of the radius.
In Type III, a major portion of the radius is missing, but a small segment closer to the elbow still remains.
In Type IV, the radius is totally absent.
Only a third of patients with underdeveloped or absent radius bone (radial dysplasia) have this as the only abnormality. A total body check-up is necessary as radial dysplasia often appears alongside other congenital (present at birth) medical conditions. Some common ones include VACTERL Association, VATER syndrome, Holt-Oram syndrome, TAR syndrome, and Fanconi anemia. Tests such as spine X-rays, renal ultrasound, complete blood count, and heart ultrasound (echocardiogram) can help identify these associated conditions.
VACTERL Association is a group of birth defects that includes spinal abnormalities, anal abnormalities, heart defects, abnormal connection between the trachea and esophagus, kidney abnormalities, and limb abnormalities. This condition is usually caused by developmental defects that occur during the formation of the baby within the womb.
Holt-Oram syndrome is another condition that is associated with heart defects and limb abnormalities (also known as heart-hand syndrome). This disorder is a result of mutations in a specific gene on chromosome 12.
In individuals with TAR syndrome, the radius bone is completely absent alongside a condition known as thrombocytopenia, which is a deficiency of platelets in the blood causing bleeding into the tissues, bruising and slow blood clotting after injury. The thumb may be present but usually underdeveloped.
Fanconi anemia is a genetic disorder that impacts the bone marrow causing decreased production of all types of blood cells, leading to anemia (reduction in number of red blood cells), leukopenia (reduction in white blood cells), and thrombocytopenia (reduction in platelets). Everyone with radial dysplasia who doesn’t have a known identifiable syndrome is advised to be tested for this potentially life-threatening blood disorder. An early diagnosis allows for time to find a bone marrow match that can potentially save the child’s life. Research studies that evaluate the effect of radiation and chemicals on chromosomes are recommended for all children with thumb and arm abnormalities.
Treatment Options for Radial Dysplasia
If your child has radial dysplasia, a condition where the radius (one of the two bones in the forearm) is malformed or missing, treatment should start soon after they’re born. This usually involves gentle stretching, manipulation, and splinting of the affected arm to help straighten it. This stretching can help make any future surgery more successful and should be continued right through to the time of surgery. You can do this with the help of specially designed splints or casts.
In some cases, a device that applies gentle external pressure might be used to help to stretch the tight tissues in your child’s arm. This device, often used before surgery, can be especially useful for children with more severe stages of radial dysplasia.
Surgery isn’t required for every child with radial dysplasia. If your child’s case is mild and their joints are stable, they may only need stretching and splinting. This is also the case for children whose other medical conditions could make surgery risky. Surgery is also avoided for children who have stiff elbows since the side bending of the wrist is necessary for these children to bring their hands to their face.
But if surgery is necessary, the aim is to straighten the forearm and increase its length. The doctor might need to remodel or remove the thumb and replace it with the index finger, a process known as pollicization. This surgery is usually done in two steps: first, the hand and wrist are aligned with the end of the forearm bone (ulna); this is generally done before your child turns one. After about six months, the next stage – thumb reconstruction or removal and index finger replacement – is performed.
The two main surgical methods to align the wrist with the end of the ulna are ‘wrist centralization’ and ‘radialization’. Both these methods help to increase the stability and functional use of your child’s hand and wrist, and results have been found to be similar in terms of correcting the deformity long term. They may also require transferring tissue, reshaping the ulna or wrist bones, or sometimes, using an external fixator and completing the realignment in a later procedure.
If your child’s affected arm is noticeably shorter than their unaffected one, the surgeon may use techniques to lengthen the ulna or other bones in the arm. However, these procedures can affect growth, so repeated procedures may be needed to ensure the length stays correct.
In cases where your child’s thumb is mildly abnormal but still functional, surgical correction may not be needed. For severe thumb abnormalities, surgery may be needed to remodel the thumb or, in some cases, remove it entirely and replace it with the index finger to create a functioning ‘thumb’.
What else can Radial Dysplasia be?
There are several other conditions doctors need to consider when trying to make a diagnosis. These include:
- TAR syndrome (a condition characterized by low platelet count and absence of the radius bone in the arm)
- Fanconi anemia (a rare genetic disorder that affects the bone marrow)
- Aneuploidy (particularly trisomies 13 and 18 – chromosomal disorders resulting in extra chromosomes)
- VACTERL (a non-random association of birth defects that affects multiple parts of the body)
- Diabetic embryopathy (birth defects caused by maternal diabetes)
- Impact of teratogens (substances that can cause birth defects)
- Ectrodactyly (a rare form of a congenital disorder where the development of the hand is disturbed)
- Amniotic band syndrome (a condition where strands from the amniotic sac separate and entangle digits, limbs, or other parts of the fetus)
What to expect with Radial Dysplasia
People may experience some degree of reoccurrence of wrist radial angulation, which refers to the twisting or bending of the wrist. Long-term studies have shown that even though children with radial dysplasia (a condition where the radius bone in the forearm is either absent or malformed) may deal with significant limitations in strength and joint mobility, they don’t usually have restrictions on their activity levels. Despite their physical challenges, these children’s participation in societal activities remains unaffected.
Possible Complications When Diagnosed with Radial Dysplasia
Studies indicate that the most common issues following wrist realignment surgeries are stiffness and the wrist returning to its previous incorrect alignment. Reconstruction surgery, another method of treating wrist issues, often has complications such as pin tract infections. Although seldom, there might also be blood circulation complications. These rare circumstances could cause long-term growth problems for the bones that were moved during surgery.
Common post-surgery complications include:
- Stiffness in the wrist
- Recurrence or return to the misaligned position
- Pin tract infections from reconstruction surgery
- Vascular, or blood circulation, complications (rare)
- Long-term growth issues in the repositioned bones due to vascular complications
Preventing Radial Dysplasia
Teaching the patient’s family about radial club hand is key to achieving the best results. Initial meetings should aim to build a strong relationship of trust, discuss what radial club hand is and any other related conditions, and give a realistic outlook for the long term. Families should also be told about other options that don’t involve surgery, as well as potential improvements in function and appearance that could come from surgery.
