A contracture occurs when a joint becomes stiff and fixed in a bent or straight position, limiting movement of that joint. Why AMC happens is not fully understood, although some arthrogryposis causes are known. Others, including genetic influences, remain under study.
This article explains arthrogryposis, some potential causes for the disorder, and its symptoms. It will help you to understand how AMC is diagnosed and treated, as well as what to know during pregnancy.
Is Arthrogryposis Rare?
Arthrogryposis develops before birth (it is a congenital defect) and in the U.S., it occurs about once per every 3,000 to 5,000 live births, affecting both males and females of all ethnic backgrounds.
More than one body part has to be affected for the disorder to be referred to as arthrogryposis multiplex congenita (AMC). Clubfoot, for example, is a congenital contracture affecting only the foot. It is an isolated congenital contracture and not arthrogryposis.
There are more than 150 types of AMC, with amyoplasia being the most common and accounting for more than 40% of all AMC cases.
Arthrogryposis Causes
Arthrogryposis is usually caused by decreased fetal movements in the womb. The fetus needs movement in the limbs to develop muscle and joints. If the joints don’t move, extra connective tissue develops around the joint and fixes it in place.
Some of the causes of decreased fetal movements are:
Malformations or malfunctions of the central nervous system, such as spina bifida, brain malformations, or spinal muscular atrophy An inherited neuromuscular disorder such as myotonic dystrophy, myasthenia gravis, or multiple sclerosis Maternal infections during pregnancy such as German measles (rubella) or rubeola Maternal fever above 102. 2 Fahrenheit for an extended period, or increased maternal body temperature caused by prolonged soaking in hot tubs Maternal exposure to substances that can cross the placenta and harm the fetus, such as drugs, alcohol, or an anti-seizure medication called phenytoin (Dilantin) Too little amniotic fluid or chronic leaking of amniotic fluid, which may limit space for the fetus to move around
Symptoms of Arthrogryposis
The particular joint contractures found in an infant with arthrogryposis vary from child to child, but there are several common characteristics:
The legs and arms are affected, with wrists and ankles being the most deformed (think of the fetus folded up inside the uterus, then locked in that position)The joints in the legs and arms may not be able to move at allMuscles in the legs and arms are thin and weak or even absentThe hips may be dislocated
Some infants with arthrogryposis have facial deformities, a curvature of the spine, genital deformities, cardiac and respiratory problems, and skin defects.
Diagnosing Arthrogryposis
Making a diagnosis of arthrogryposis multiplex congenita (AMC) is difficult when a fetus is still developing. There is no prenatal test for the disorder. Some AMC changes may be detected during ultrasound examinations, but the majority of them (about three-fourths) can be seen only after 24 weeks of gestation.
However, people with a history of AMC during previous pregnancies can be monitored more closely. There is a genetic link in some but not most cases. An obstetrician-gynecologist (OB-GYN) may recommend genetic testing as part of a diagnosis in specific cases.
An AMC diagnosis is confirmed when a newborn has joint contractures in two or more places. Part of the diagnosis will include testing for other conditions that may be the cause, or related to, the development of AMC, including brain, heart, and eye disorders.
Some of these conditions will involve severe and potentially fatal outcomes, including stillbirth, but many children who receive treatment for AMC will have generally normal life expectancy.
Arthrogryposis Treatment
Arthrogryposis cannot be cured, but treatment is directed towards specific symptoms. For example, early vigorous physical therapy can help stretch out the contracted joints and develop the weak muscles.
Splints can also help stretch joints, especially at night. Orthopedic surgery may also be able to relieve or correct joint problems.
Ultrasound or computed tomography (CT) scans can identify any central nervous system or other abnormalities. These may require surgery to treat, such as congenital heart defects that may need to be repaired.
Keep in mind that AMC is not a progressive disease. This means it will not get worse over time, and people born with it often experience lives that are full, self-sufficient and successful.
In fact, one long-term study of 65 adults born with AMC found that 38 of them went to college, the same number were married, 34 had children of their own, and only 10 lived lives that were fully dependent on others.
Arthrogryposis Prognosis
The lifespan of an individual with arthrogryposis is usually normal but may be altered by heart defects or central nervous system problems. In general, the prognosis for children with amyoplasia is good, though most children require intensive therapy for years. Almost two-thirds are eventually able to walk (with or without braces) and attend school.
