Congenital hand and arm deformities can be any abnormalities or differences that affect the shape and/or functionality of the shoulder, arm, elbow, forearm, hand, or fingers when a baby is born. Hand and arm differences or deficiencies include missing, incomplete or malformed limbs, extra fingers, an incomplete separation of the fingers, or various other differences in upper extremity growth.
The cause of most congenital hand and bone malformations is unknown. Some, however, are known to be hereditary and may be identified with genetic testing and/or genetic counseling of parents. Some others result from systemic diseases such as Holt-Oram Syndrome, arthrogryposis multiplex congenita, or multiple hereditary exostosis. Advances in molecular biology and genetics have helped doctors better understand some of these conditions, as well as redefine previous classification systems, even if not all causes have been identified.
There are numerous types of upper extremity deficiencies: growth in the arms or hands may be halted, leading to shortened or missing fingers; duplicated, leading to extra fingers (known as polydactyly); or malformed, leading to problems such as conjoined fingers (syndactyly) or abnormally curved fingers (clinodactyly). In the forearm, longitudinal deficiencies – in which all or part the radius or ulna bone are missing – causes upper limb length discrepancies and/or inward or outward angling of the hand.
The most common congenital difference in the upper limbs is syndactyly, where the fingers do not separate. HSS treats the following congenital hand and upper limb differences:
This is an abnormal curvature of one finger towards an adjacent finger. This most commonly affects the small finger, also known as the “little finger” or “pinky.” Most cases involve mild clinodactyly in the small finger, and even moderate curvature of the fingers are well tolerated. Severe deformity can get in the way of gripping and even getting hands in the pockets.
Camptodactyly means “bent finger” in Greek. Children with camptodactyly are unable to straighten their finger(s) completely. This can happen from birth, or can develop later on in life, typically during adolescence. The cause of camptodactyly is unknown.
Also referred to as split hand or cleft hand, in ectrodactyly, a child will be missing at least the long, middle finger. In other cases, more fingers or even all them may be absent.
In the sixth to seventh weeks of embryogenesis, the developing embryo grows a hand paddle. That hand paddle then typically cleaves over time in four places to give us four fingers and a thumb. If the center cleavage is too deep, the web space between the index and ring fingers will be so deep that the middle finger will not form. In more severe cases, the cleft will be so extensive that only the small finger, or no fingers, will remain. Cleft hand is a condition that tends to run in families, but new mutations in people with no family history are also common. Children with cleft hands often have other congenital differences, including a cleft foot and/or a cleft lip and palate. Children with a condition known as ectrodactyly ectodermal dysplasia cleft lip/palate syndrome (sometimes shortened to EEC syndrome) also have problems in ectodermal (outer portion of the embryo) elements as well, such as with hair, nails, sweat glands, and skin.
Also known as constriction ring syndrome or amnionic band, constriction band occurs when an egg’s amnion (a thin membrane that lines the) breaks loose during development in the uterus and gets tangled around the developing fetus’s legs or arms. In mild cases, this just leads to a crease (or “band”) in the skin. When such bands occur around the developing fingers or toes, it can cause them to become stuck together. In rare, severe cases, the amnionic bands can strangulate a limb, requiring an amputation after birth.
Constriction bands are less common than is usually reported, because many children diagnosed with the condition in fact have a different condition that shares visual similarities, such as symbrachydactyly or cleft hand.
This is a spectrum of conditions ranging from a short but otherwise normal thumb, to one that is absent of tendons or ligaments, to a completely missing thumb and even a small or missing radius bone of the forearm.
All children with a small or absent thumb should be screened for heart, kidney, spine, tracheal, esophageal, and anal abnormalities, which are associated with VACTERL syndrome (Vertebral defects, Anal atresia, Cardiac defects, Tracheo-esophageal fistula, Renal anomalies, and Limb abnormalities). Genetic testing and a chromosomal challenge test should be performed to rule out inheritable causes such as Holt-Oram (HOS) and Diamond-Blackfan Syndromes and Fanconi Anemia.
If both thumbs are small and the radius bones are absent in the forearm this can be associated with thrombocytopenia, which can make clotting of the blood difficult. This condition is called thrombocytopenia absent radius (TAR).
In some cases of hypoplastic thumb, the radius bone in the forearm may also be small or missing, and the entire forearm may be short with a medial (inward) angle of the wrist. This is known as radial longitudinal deficiency or radial club hand.
This is a spectrum of conditions in which part or even all the ulna bone of the forearm is missing. Ulnar longitudinal deficiency is also known as ulnar dysplasia or ulnar club hand. Frequently the small and the ring fingers will be missing as well, and the elbow may be fused. The thumb can be affected as well.
Macrodactyly is an abnormal enlargement of the finger. Children with macrodactyly often have hemihypertrophy, or enlargement of the entire limb as well. Children should be screened for Wilms tumors of the adrenal glands and other abdominal tumors with ultrasounds every three months until six years of age.
Also known as Madelung’s disease or Madelung deformity, this is a decreased or complete failure of growth in one corner of the distal radius at the wrist (the end of the radius bone that is closer to the hand).
Madelung causes deformities as well as pain in the wrist. It is more common in females than in males, and it is often associated with Leri Weill dyschondrosteosis, also with mesomelic (forearm) shortening and short stature. The ulnar bone can become prominent and look like a tumor on the pinky side of the wrist. The entire radius can be affected and in severe cases the hand can look like it is attached to the side of the forearm.
Polydactyly is where extra fingers grow in the hand. Some are functional but most are just in the way. Most cases of polydactyly run in families and can be present on both sides and both the hands and feet. Learn more by reading Polydactyly (Extra Fingers or Toes) and Corrective Surgery.
Symbrachydactyly is a hand difference resulting in short fingers, webbed fingers, and/or missing fingers. This condition may be associated with other upper limb differences, including absence of chest wall musculature called Poland Syndrome. Most children diagnosed with constriction bands actually have symbrachydactyly.
Syndactyly is webbed or conjoined fingers. This condition occurs in about 7 out of every 10,000 live births and most commonly affects the middle and ring fingers. Simple syndactyly is fusion only of soft tissue, while complex syndactyly is when finger bones are conjoined. Learn more by reading Syndactyly (Conjoined Fingers or Toes) and Corrective Surgery.
Surgical procedures vary widely, depending on the particular problem. Limb lengthening surgery may be an option for some longitudinal deficiencies. Surgeries for the hand and fingers include building a new thumb out of the index finger(pollicization), creating thumbs and fingers out of toes, removing extra fingers, straightening the wrist, separating fingers, and closing gaps in the hand.