bubble_chart Overview

Arthrogryposis multiplex congenita is a syndrome characterized by the fibrosis of muscles, joint capsules, and ligaments, leading to stiffness in multiple joints throughout the body.

bubble_chart Etiology

It is generally believed that the loss of fetal limb movement within the uterus is the fundamental mechanism of this disease. It has been demonstrated that many factors, such as the injection of certain drugs during pregnancy or viral infections, can cause the fetus to lose limb motor function and develop this condition. Drachman injected curare into the blood vessels of the chorioallantoic membrane of chicken embryos, creating an animal model of multiple joint contractures. Moessinger also injected curare into the uterus of rats, resulting in multiple joint contractures, pulmonary hypoplasia, micrognathia, and a short umbilical cord, among other deformities. Jago reported a case where a mother, during the 10th to 12th weeks of pregnancy, was injected with muscle relaxants due to tetanus, leading to the birth of an infant with multiple joint contractures. Certain viruses, such as Newcastle virus, Akabane virus, and Coxsackie virus, have been proven to play a pathogenic role in this disease through animal experiments.

bubble_chart Pathological Changes

Pathologically, it can be divided into two entirely distinct pathological changes: the neural type and the muscular type. In the pathological changes of the neural type, the most significant features are the disappearance, degeneration, or reduction in size of the anterior horn cells of the spinal cord. Other pathological changes include thinning of the cervical and lumbar spinal cord and a reduction in the number of anterior spinal nerve roots. However, the posterior horn, lateral horn of the spinal cord, or dorsal root ganglion cells show no abnormalities. Brain damage includes cerebral hypoplasia, incomplete sulcus formation, lateral ventricular enlargement, and reduction in the size of Betz cells in the cortex. The severity of these neurological lesions determines the pathological changes in the muscles of the affected limbs. The volume, color, and texture of the limb muscles may appear entirely normal, or the volume may decrease or even disappear completely. Microscopically, a reduced number of muscle fibers and a decrease in muscle fiber diameter can be observed, though striations are often preserved. The articular cartilage in the initial stage [first stage] may appear entirely normal, but in older children, destruction of the articular cartilage occurs, accompanied by degenerative changes. The joint capsules of the affected joints also thicken due to fibrosis.

The muscular type shows no primary lesions in the anterior horn of the spinal cord, nor any abnormalities in the brain or motor branches of the nerves. The affected muscles appear grayish-white in color, with a tough, fibrous texture. Microscopically, the affected muscles exhibit fibrous and fatty degeneration, with a disorganized distribution of both thick and thin muscle fibers, and an increase in intramembrane fibrous components. The pathological changes in the articular cartilage and joint capsules are similar to those seen in the neural type.

bubble_chart Clinical Manifestations

The clinical manifestations of this disease are very complex. Hall classified the disease into three major categories based on the extent of the lesions. The first category involves only the limb joints, accounting for about 50%; the second category is arthrogryposis accompanied by visceral and craniofacial deformities; the third category is arthrogryposis accompanied by neurological abnormalities.

**First Category**: This can be further divided into two subtypes: muscular hypoplasia and distal limb arthrogryposis. The former is the typical form of arthrogryposis. Usually, shortly after birth, symmetric stiffness of the limb joints can be observed, often fixed in a flexed position, though sometimes in an extended position, with a few degrees of residual flexion or extension movement. The affected limbs show significant muscle atrophy and cylindrical deformities of the knees and elbows. Due to the loss of normal skin texture, the skin appears shiny and taut, giving the patient a puppet-like appearance. When joints are fixed in flexion, the skin and subcutaneous tissues may form webbed deformities. Skin sensation is normal, but deep tendon reflexes are often weakened or absent. Although all limbs may be affected, involvement of all four limbs occurs in 46% of cases, lower limbs alone in 43%, and upper limbs alone in 11%. When the lower limbs are affected, the feet often exhibit metatarsus adductus varus, knee flexion or extension, hip flexion with external rotation and abduction, or hip flexion-adduction contracture with dislocation. Additionally, 20% of patients develop advanced-stage C-shaped scoliosis. Upper limb deformities include internal rotation of the shoulders, flexion or extension of the elbows, radial head dislocation, forearm pronation, and wrist flexion contracture. The thumbs are often adducted and flexed against the palm, with proximal interphalangeal joint flexion contractures.

The distal contracture subtype affects only the hands and feet, with the thumbs flexed and adducted across the palm, while the other four fingers are flexed into a fist-like position, overlapping each other. Foot deformities commonly include metatarsus adductus varus, though calcaneovalgus deformities may also occur, accompanied by toe flexion contractures.

**Second Category**: In addition to arthrogryposis, deformities in other areas are present, such as Marfan syndrome, Freeman-Sheldon syndrome, and pterygium syndrome.

**Third Category**: Arthrogryposis is accompanied by severe neurological abnormalities, such as trisomy 18, 9, or 8, brain malformations, and meningocele. These are typically autosomal abnormalities and can be diagnosed through peripheral blood karyotyping, though most infants die early.

bubble_chart Treatment Measures

The treatment of this disease faces many challenges, as multiple affected joints often require repeated surgeries. The postoperative recurrence rate is high, necessitating recurrent surgical interventions. However, most affected children exhibit higher intelligence than average, and with effective treatment, they can achieve remarkable self-care abilities. Therefore, both physicians and parents should maintain confidence. The treatment goals are to increase the range of motion in affected joints, enable independent or assisted walking, and maximize the functional use of the upper limbs and hands. To achieve these objectives, the following principles must be followed: 1. Early soft tissue release is essential. Incising or excising joint capsules, ligaments, or contracted muscles that restrict joint movement can restore a functional range of motion. Since contracted soft tissues are often tough and rigid, physical therapies such as passive stretching or manual tuina are not only ineffective but may also increase joint pressure, leading to cartilage necrosis. 2. Although physical therapy alone often lacks corrective effects, when combined with soft tissue release, persistent physical therapy can help maintain surgical outcomes and delay recurrence. 3. Orthotic devices provide supplementary support. Nighttime wear helps maintain surgically corrected positions, while daytime use assists in walking. 4. Due to the tendency for postoperative recurrence, muscle-tendon transfers can be employed to replace fibrotic or weakened muscles, achieving muscle balance and improving limb function. However, the outcomes of such procedures are inferior to those seen in similar surgeries for poliomyelitis.

Guided by these principles, the surgical method should be selected based on the specific nature and severity of the deformity, as well as the patient's age. Clubfoot and calcaneovalgus foot are common foot deformities in this condition and require early surgical treatment. Typically, infants can undergo surgery at 3 months of age, with preoperative Gypsum fixation to stretch the tight skin. During surgery, the contracted joint capsules and ligaments should be excised. For clubfoot deformity, thorough peritalar release and central reduction of the talocalcaneonavicular joint should be achieved. If the lateral column of the foot hinders reduction, the anterior part of the calcaneus (Lichtblau procedure) or the calcaneocuboid joint (Evans procedure) may be excised. Postoperatively, the foot may become stiff but can bear weight on the metatarsus for walking. If open reduction for calcaneovalgus foot proves difficult, excision of the navicular bone can facilitate the formation of a ball-and-socket joint between the talus and the first to third cuneiform bones, while also preventing talar avascular necrosis. Knee flexion contractures are relatively common. Grade I flexion (<20°) does not affect function and can be managed with nighttime bracing to prevent worsening with age. Grade II knee flexion deformities (20°–60°) should be treated early with surgery, primarily involving posterior capsulotomy and hamstring lengthening. If collateral ligaments and the anterior cruciate ligament contracture hinder knee extension, these ligaments can be lengthened in young children. For older children, supracondylar femoral extension osteotomy is preferred. For flexion deformities exceeding 60°, soft tissue release may risk injury to the sciatic nerve and popliteal vessels, necessitating bone shortening and extension osteotomy. Another option is anterior epiphysiodesis of the distal femur and proximal tibia, though results are often unsatisfactory. Knee extension deformities are less common. In neonates, manual stretching and bracing may suffice. If the deformity persists beyond 6 months of age, quadricepsplasty can yield satisfactory results, with long-term nighttime bracing to reduce recurrence rates. Hip deformities are more complex and can be categorized into: 1. Hip deformities with dislocation and 2. Hip deformities without dislocation. Hip dislocation may be unilateral or bilateral. Bilateral dislocations with joint stiffness are best left untreated, as surgical intervention may result in stiff hips without or with partial dislocation, which are functionally worse than stiff dislocated hips. For unilateral dislocations with stiffness, combined soft tissue release, open reduction, and femoral shortening osteotomy can improve hip function. Bilateral dislocations without stiffness should undergo surgical release and open reduction, followed by abduction bracing for 3–6 months. Hip deformities without dislocation include: ① abduction, external rotation-flexion deformity; ② pure abduction deformity; ③ pure extension deformity; and ④ pure flexion deformity. Among these, abduction, external rotation-flexion deformity is most common. Unilateral cases often lead to scoliosis, while bilateral cases result in clumsy gait. Treatment may involve iliotibial band release, tensor fasciae latae and iliopsoas tenotomy or lengthening. Abduction deformity is rare and may require release of the gluteus medius, minimus, and fascia. Pure hip flexion deformity is more common but usually mild, manageable with bracing or prone sleeping; severe cases may need surgical release of hip flexors. Pure hip extension deformity is very rare and may require release of the gluteus maximus, posterior fascia, and ligaments.

Upper limb joint contractures commonly manifest as deformities of the elbow, wrist, and fingers. In elbow flexion contractures, the biceps brachii and brachioradialis often retain some function, while the triceps are weak, with thickened and contracted joint capsules and ligaments on the flexor side. Mild cases are treated with passive stretching and Gypsum fixation in elbow extension, supplemented by nighttime orthotic use to maintain correction. More severe elbow flexion contractures require surgical release and lengthening of the biceps brachii and brachialis, followed by orthotic fixation to prevent recurrence. Elbow extension contractures are more complex, often accompanied by forearm pronation, wrist flexion, and finger deformities. Here, the triceps are relatively strong, while the biceps are weakened or entirely absent. Passive stretching and Gypsum correction not only fail to address extension deformities but may also lead to articular cartilage necrosis and intra-articular adhesions, exacerbating elbow stiffness. Since elbow extension deformities significantly impair upper limb function—such as eating and toileting—surgical intervention is necessary. Procedures include triceps tendon lengthening, posterior elbow joint capsule and ligament release, and triceps or pectoralis major transfer to reconstruct elbow flexion. Triceps lengthening and posterior capsule release can markedly improve elbow flexion, but due to weak flexor muscles, recurrence is common. Therefore, for children over 5 years old who can participate in rehabilitation, triceps or pectoralis major transfer for flexion reconstruction is preferred. However, in cases requiring crutch use or wheelchair mobility, maintaining elbow extension may be more functional. If bilateral extension deformities exist in such patients, only one elbow should undergo flexion reconstruction to avoid compromising assistive device use. Wrist flexion contractures are not only common but often severe (up to 90°) and accompanied by ulnar deviation. Early correction significantly improves function, with some advocating passive stretching and Gypsum splinting starting days after birth, alongside thumb and finger deformity correction. Fixed wrist flexion contractures respond well to serial Gypsum casting. However, weak wrist extensors increase recurrence risk; early transfer of the flexor carpi ulnaris to restore extension may be warranted. Williams recommends internal fixation with intramedullary nails after age 6 to stabilize the wrist, fixing the metacarpophalangeal joint at 5° flexion until skeletal maturity, followed by wedge resection and Gypsum fusion. Tachdjian employs dorsal wedge osteotomy of the distal radius and ulna for severe wrist flexion stiffness, correcting deformity while relatively lengthening flexor muscles and soft tissues. Forearm pronation contractures are effectively treated by pronator teres release or transfer to restore supination. Thumb adduction-flexion deformities often stem from hypoplasia or absence of the extensor pollicis longus, brevis, and abductors, leading to adductor contractures, purlicue soft-tissue tightness, and interphalangeal joint limitations that severely impair opposition and grasp. Passive stretching and splinting are used in infancy; purlicueplasty, adductor release, and extensor pollicis lengthening or transfer improve function in early childhood. Flexion contractures of the fingers, though common, are usually mild. Early passive stretching and nighttime splinting prevent progression. Severe cases require release of the flexor digitorum superficialis and collateral ligaments, with temporary K-wire fixation. If dorsal release improves extension but induces wrist flexion, fractional lengthening of the flexor digitorum profundus and superficialis at the musculotendinous junction is performed. Postoperative Gypsum or prolonged nighttime orthotic use minimizes recurrence.

bubble_chart Differentiation

Patients with typical signs, such as limb muscle atrophy and symmetric joint contractures, while maintaining normal skin sensation, are easily diagnosed. However, for the distal limb contracture type, where hand and foot deformities gradually worsen—especially in those who seek medical attention late—it is necessary to differentiate from rheumatoid arthritis and congenital bone and joint deformities. Nonetheless, the hand and foot deformities in such patients are also symmetrically distributed, which is a characteristic of this disease. Additionally, laboratory tests often show no abnormal findings.