Arthrogryposis is a name given to a large group of medical conditions in which multiple joints are severely fixed and immobilized by the formation of contractures present at birth, but not progressing thereafter. The term contracture refers to the formation of fibrous connections across joints, which results in very limited or absent joint mobility. When only one joint is affected by a contracture, the condition is not called arthrogryposis.
Arthrogryposis is by definition non-progressive, affects multiple joints, and is present at birth. Also called arthrogryposis multiplex congenita (AMC), it is a disabling condition. It may affect joints in the arms or legs, though the latter are more commonly affected. Both large and small joints are likely to show contractures. The parents of the affected child are usually normal, but the condition itself is due to a defect in any of over 125 genes, caused by a fresh mutation. It is therfore possible for AMC patients to pass the defective gene on to their offspring.
The most common condition presenting with AMC is called amyoplasia, and is responsible for 40% of cases. In these children, the contractures may force the affected joints into either a bent or straight position.
How arthrogryposis occurs
The joints of the body form early in embryonic life, but they need to be moved normally throughout intrauterine life in order to attain their full development and range of mobility. Lack of this normal joint movement in fetal life, which is called fetal akinesia, is responsible for the formation of contractures. Fetal akinesia is associated with several conditions:
- a very low liquor volume (oligohydramnios)
- amniotic bands
- cord entanglement
- maternal alcohol abuse
- the use of drugs like phenytoin
- multiple pregnancies
- certain nervous system conditions
- muscle or connective tissue abnormalities
- high body temperatures during pregnancy
Risk factors for arthrogryposis
AMC occurs in 1 in 3,000 births, and shows a wide spectrum of severity. It is more common in infants born to older parents or to parents with a history of consanguinity, which increases the risk of rare autosomal recessive diseases.
An autosomal recessive condition is inherited from both parents, each having one abnormal copy and one normal copy of the same gene. Neither parent shows any signs or symptoms of the disease condition, since the normal copy compensates for the abnormal. However, when each passes the abnormal copy of the same gene to the baby, the child will inherit two defective copies of the gene and express the disease.
The risk of having a baby with AMC is enhanced if there is any history of similar contractures, even if only in infancy, on either side of the family.
The risk is also higher if the mother has a history of myasthenia gravis, myotonia dystrophica or multiple sclerosis. Certain ethnic communities such as the Israeli Bedouins also have a higher incidence.
Diagnosis is by observing multiple fixed contractures in the infant. At birth, multiple joints such as the baby’s elbows, knees, wrists, ankles, shoulders and/or hips are fixed or dislocated. There are wing-shaped membranes spanning the neck, fingers, knees and elbows, or ankles, and these are called pterygia.
The presence of multiple, bilaterally symmetrical contractures is the hallmark of this condition. A characteristic feature is that the more distal the contracture is, the more severe it will be.
X-rays and other advanced imaging techniques may be useful in showing the extent of involvement. There may be many other associated malformations and deformities of the skull, heart or kidneys, among other organs. Intelligence is normal in many affected children.
The family of the affected child needs to be tested for suspicious features such as the presence of hyperextensile joints, joint dislocation, or bilateral club feet, or a history of congenital contractures in infancy. This will help to screen for the presence of the abnormal gene in any other members of the family.
Most patients survive the period of infancy, except in some cases when the brain and spinal cord are also affected as well as the joints. Half the babies in this latter group die within the first year.
Treatment is aimed at helping the patient and family through the phases of accepting the diagnosis and supporting them through rehabilitation. A long course of physical therapy is needed to restore the range of motion of the joints and stretch the tight tissues. At the same time, serial casts or splints may be applied every week to help maintain the joints in the new position. Surgery is often required to release very tight or dense fibrous adhesions, reduce hip dislocations, lengthen the bones or to stabilize the spine if it is damaged.
Physical and occupational therapy is essential to find alternative ways for the child to perform necessary movements such as rolling over, sitting up, crawl and walk. At the same time the baby is trained to be as independent as possible. This training will eventually cover most aspects of life, whether it is eating, dressing or moving from his chair. It is also important to use the right tools to increase the child’s mobility and independence. A wheelchair or walker, for instance, may be used to help the child to get around on his own. Arm braces help support the child’s arm so he can feed himself.
An effective curative treatment of Arthrogryposis does not yet exist. Even after remarkable corrections have been made, the unpredictable demands of the growth spurt can cause contractures to recur after therapy. Thus the child often requires long-term therapy to make him as mobile and independent as possible.