Arthrogryposis/Arthrogryposis Multiplex Congenita (AMC)
At SSM Health Cardinal Glennon Children’s Hospital, we are leaders in the treatment of individuals with AMC.
Arthrogryposis multiplex congenita (AMC), or simply arthrogryposis, is a rare congenital condition where babies are born with multiple stiff and contracted joints. It is diagnosed in approximately one out of every 3,000 births.
Arthrogryposis is sometimes found during pregnancy by ultrasound, but more often it is diagnosed after a baby is born, with babies having different levels of contracture. Such contractures impact both flexibility and range of motion and can affect the ability to sit and walk. Arthrogryposis is not a progressive disorder and with prompt medical care and physical therapy, children can lead productive and independent lives long into adulthood.
Babies with mildly contracted joints respond well to simple stretching. In severe cases, there is limited range of motion in all joints. Because of the contractures, infants also may have lung and brain problems that need to be treated.
There are hundreds of conditions or diagnoses that have symptoms that are like arthrogryposis. That’s why an early medical evaluation is so important. One thing all these conditions have in common is that the developing baby does not move appropriately in utero. As a result, there is shortening and tightening of the muscles and tendons around one or more joints, leading to contractures. The longer that a joint does not move or is stiff, the more severe the contracture.
Types of Arthrogryposes
There are several types of arthrogryposes, some are caused by the lack of movement in the womb, others are caused by a gene mutation passed down by a mother and/or father, and still others are the result of an infection during pregnancy. Illnesses such as myasthenia gravis or multiple sclerosis have been associated with arthrogryposis in rare cases. Zika virus, rubella, and rubeola are some of the diseases that are linked to arthrogryposis.
Broad Types Include:
Amyoplasia
This is the most common type and accounts for at least half of the children diagnosed with AMC. It results in a lack of muscle development in the upper and/or lower limb joints — the hands, wrists, elbows, or shoulders, or the hips, knees, or feet. More than half of the children diagnosed with amyoplasia will have all four extremities involved. A smaller percentage will have only their legs involved and about 10% will have just arms involved. In more severe cases, contractures also can occur in the jaw or spine. Once born, babies may have a midline congenital hemangioma (red spot) on the forehead, nose, or chin, which usually fades over time. The arm and leg contractures usually look the same from side to side, with the shoulder turned inwards, the elbows usually straight but sometimes bent, and unusually stiff fingers. Hips are usually flexed and turned out and knees either have contractures or are straight and stiff. Clubfeet are extremely common in children with amyoplasia, but the feet are stiffer than usual.
Distal arthrogryposis (DA)
These are caused by a gene mutation and result in contractures that affect primarily the hands and feet (the “distal” joints). Currently, there are 19 recognized types of DA. Some of them also affect the face, and babies may have a small mouth opening and deep-set eyes. A severe curvature of the spine (scoliosis) also may be noticed.
Escobar syndrome/Pterygium syndrome
Also genetic, this is caused by a gene mutation carried by both parents. The word pterygium means “winging” or “webbing” of a joint. Not only do the joints have contractures which make them stiff to move, but some joints also will have excess skin that tethers or “wings” from one joint to another, preventing full movement. For example, a severe knee pterygium would have the skin from back of the upper thigh run in a straight line to the heel, instead of curving in behind the knee.
Treatment Options
A multidisciplinary team approach to treating children and adults with AMC can improve function, decrease pain, and enhance overall quality of life.
- Physical therapy often begins within weeks of birth, first emphasizing stretching of the contracted joints and then adding strengthening and mobility exercises.
- Occupational therapy focuses on fine motor skills, such as grasping food or objects and tasks of daily living.
- Speech therapy may be needed to address swallowing issues and any problems with talking.
Treating AWC Orthopedic Problems
Pediatric orthopedic surgeons will evaluate and treat problems related to joint stiffness and contractures. Options to minimize or correct contractures in the feet, knees, hip, or spine include:
- Progressive bracing or casting (Ponsetti method)
- Use of orthotics
- Releasing and lengthening of tight muscles and tendons
- Changing the rotation of a malformed bone or joint
- Lengthening of bones
- Muscle or tendon transfers
Hip Contractures
Hip contractures are the most important issue to fix so that a child has a chance at functional walking. With severe foot deformities or knee contractures, a child can still get the foot underneath the body to stand or walk, but with hip contractures it may not be possible to position the body over the feet. Hip contractures can vary from mild to severe, and treatment needs to be individualized. The important concept is to not weaken the hip muscles when improving the hip motion. In mild or moderate cases, the contracted structures can be released through a small ½-inch incision just to the outer edge of the groin. More severe hip deformities may require a “proximal femoral re-orientational osteotomy,” a procedure where the top of the thigh bone (femur) is cut and the leg realigned appropriately with the body.
Congenital Hip Dislocations
Approximately one-third of hips with contractures also will be dislocated at the time of birth. The difference with these dislocations associated with AMC is that they are stiffer and more displaced. In the past there were concerns that surgery to correct the problem would lead to stiffness, but many follow-up studies have shown that putting the hips back into their sockets early improves walking efficiency with little impact on hip motion. Our own studies found on average that only 4 degrees motion was lost compared to hip motion before the operation, which is far too small of a change to have any effect on how the hip functions.
Flexion Contractures
Bent knees (flexion contractures) are more common than straight knees (extension contractures) at birth in children with AMC. Flexion contractures can be mild (< 30 degrees), moderate (30–50 degrees), or severe (> 50 degrees). Mild to moderate contractures can be treated with “growth guidance” – slowing down the front of the growth plate just above the knee joint to guide the femur bone to grow in such a way that the knee becomes straighter. This is done by placing small metal plates along the front of the growth plate, which are removed once the knee is straight. Moderate contractures can be treated with growth guidance, but children may also need releases of the soft tissues behind the knee (tendons, ligaments, and joint capsule) to better allow the knee to undergo its correction. In severe contractures, the stiff tissues behind the knee prevent full correction using the guided growth procedure. Instead, a release is done, followed by placing an external fixator across the knee. An external fixator is an apparatus where pins are inserted through skin into bone and are connected outside the leg by a frame with hinges at the knee. This allows the knee contracture to be gradually straightened over the course of weeks, so that the skin, nerves, arteries, and other tissues can be slowly stretched out. Regardless of how the knee contracture is corrected, a Knee Ankle Foot Orthosis (KAFO) is used at nighttime for many years to maintain the correction.
Extension Contractures
Extension contractures sometimes respond well to serial casting in young children, followed by loosening up the tight tissues in front of the knee. Older children with more rigid contractures likely require a more extensive procedures, including release of the tight tissues and possibly a shortening of the thigh bone (femur). Maintaining knee flexion range in the months after surgery can difficult, requiring an emotionally mature patient and diligent physical therapy.
Spine deformities such as scoliosis can occur in 1:4 or 1:5 children with arthrogryposis, with some conditions at a much higher risk than others (e.g., Escobar syndrome, Freeman-Sheldon syndrome). Some babies are born with spinal curves, called “prenatal” scoliosis. Others can develop scoliosis as infants or as much older children.
In the young child with severe curve, body casting can decrease the size of curves, making later bracing treatment more successful. In the older child with a curve too large for a brace, orthopedic surgeons can implant expandable rods next to the spine, which then allows the rods to be lengthened over time to keep up with the growth of the spine. Spinal fusion for arthrogrypotic scoliosis is common and effective for large curves in older children. The goal is to stop the curve from continuing to worsen during adulthood.
Orthopedic Outcomes
It is important for new parents of a baby with arthrogryposis to appreciate how well most adults can handle many daily living activities. According to research, the majority (between 49% and 88%) can walk well. Many also can drive a car (between 48% and 86%). It is still a challenge for many adults to live fully independently; however one-third to one-half of adults say they do, and they are usually limited if hand contractures make self-care tasks difficult to do. As treatment protocols and assistive technologies continue to develop, the ability to live independently should continue to improve.
For more information about the treatment of children and adults with AMC, call 314-268-4010.
