bubble_chart Overview

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

bubble_chart Etiology

It is generally believed that the loss of limb movement ability in the fetus within the uterus is the fundamental mechanism of this disease. It has been proven 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 induced multiple joint contractures, pulmonary hypoplasia, micrognathia, and a short umbilical cord in mice by injecting curare into the uterus. Jago reported a case where a mother, during the 10th to 12th week of pregnancy, was injected with muscle relaxants due to tetanus, resulting in the birth of an infant with multiple joint contractures. The pathogenic effects of certain viruses, such as Newcastle virus, Akabane virus, and Coxsackie virus, on this disease have been demonstrated in 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 decrease in the number of anterior spinal nerve roots. However, the posterior horn, lateral horn, or dorsal root ganglion cells show no abnormalities. Brain damage includes cerebral hypoplasia, incomplete sulcus formation, lateral ventricle 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, on the other hand, 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, with a tough, fibrous texture. Microscopically, the affected muscles exhibit fibrous and fatty degeneration, with a disorderly 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 highly 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; and the third category is arthrogryposis accompanied by neurological abnormalities.

**First category**: This can be further divided into two subtypes: muscle hypoplasia and distal limb joint contractures. The former is the typical arthrogryposis. Usually, symmetrical stiffness of the limb joints can be observed shortly after birth, often fixed in a flexed position, though it may also be fixed in an extended position, but usually retains the last few degrees of flexion or extension. The affected limbs show significant muscle atrophy and cylindrical changes in the knees and elbows. Due to the loss of normal skin texture, the skin appears shiny and tight, giving the patient a puppet-like appearance. When the joints are contracted in a flexed position, the skin and subcutaneous tissue 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, the lower limbs alone in 43%, and the upper limbs alone in 11%. When the lower limbs are affected, the feet often exhibit metatarsus varus deformities, flexion or extension of the knees, and flexion-external rotation or abduction of the hips, or flexion-adduction contractures of the hips 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, dislocation of the radial head, pronation of the forearms, and flexion contractures of the wrists. The thumbs are often adducted and flexed against the palm, with flexion contractures of the proximal interphalangeal joints.

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

**Second category**: In addition to joint contractures, there are deformities in other areas, 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, cerebral malformations, and meningocele. These are usually autosomal abnormalities and can be diagnosed through peripheral blood karyotyping, but infants often die early.

bubble_chart Treatment Measures

The treatment of this disease faces many challenges, as multiple affected joints often require multiple surgeries. The postoperative recurrence rate is high, necessitating repeated operations. However, children with this condition typically have higher IQs 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 the child to walk independently or with assistance, and maximize the functional use of the upper limbs and hands. To achieve this, the following principles must be followed: (1) Early soft tissue release is essential. Incising or removing certain joint capsules, ligaments, and contracted muscles that restrict joint movement can restore some 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 pressure on the joint cartilage, leading to necrosis. (2) Although physical therapy alone often lacks corrective effects, when combined with soft tissue release, persistent physical therapy can help maintain surgical results and delay recurrence. (3) Orthotic devices provide supplementary support. Wearing them at night helps maintain surgically corrected positions, while daytime use assists with walking. (4) Due to the tendency for postoperative recurrence, muscle-tendon transfers can be used to replace fibrotic or weakened muscles, achieving muscle balance and improving limb function. However, the outcomes of such procedures are less effective compared to 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, surgery can be performed when the child is 3 months old, with preoperative Gypsum fixation to stretch the tight skin. During surgery, the contracted joint capsules and ligaments should be excised. For clubfoot deformity, complete 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, although the foot may remain stiff, it 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, also preventing avascular necrosis of the talus. Knee flexion contracture is 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 deformity (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 knee flexion deformity 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 deformity is rare. 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 postoperatively to reduce recurrence rates. Hip deformities are more complex and can be categorized as: 1. Hip deformity with dislocation 2. Hip deformity without dislocation Hip dislocation may be unilateral or bilateral. Bilateral dislocation with joint stiffness should not be treated surgically, as it may result in stiff hips without or with partial dislocation, which functionally perform worse than bilateral dislocated stiff hips. For unilateral dislocation with stiffness, comprehensive soft tissue release, open reduction, and femoral shortening osteotomy can improve hip function. For bilateral dislocation without stiffness, surgical release and open reduction are recommended, followed by 3–6 months of abduction bracing. Hip deformities without dislocation include: (1) Abduction, external rotation-flexion deformity (2) Pure abduction deformity (3) Pure extension deformity (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 an awkward gait. Treatment may involve iliotibial band release, tensor fasciae latae and iliopsoas tenotomy or lengthening. Abduction deformity is rare and may require surgical 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 require surgical release of hip flexors. Pure hip extension deformity is very rare and may necessitate surgical release of the gluteus maximus, posterior fascia, and ligaments.

Upper limb contractures commonly manifest as deformities of the elbow, wrist, and fingers. In elbow flexion contractures, the biceps brachii and brachioradialis often retain some function, but the triceps is weak, and the anterior joint capsule and ligaments become thickened and contracted. Mild cases are treated with passive stretching and elbow extension cast immobilization, supplemented with nighttime orthotic use to maintain correction. More severe elbow flexion contractures require surgical release and lengthening of the biceps brachii and brachialis, followed by postoperative orthotic fixation to prevent recurrence. Elbow extension contractures are more complex, often accompanied by forearm pronation, wrist flexion, and finger deformities. In these cases, the triceps is relatively strong, while the biceps is weakened or completely absent. Passive stretching and cast 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—affecting daily activities like eating and toileting—surgical intervention is necessary. Surgical options 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/ligament release can markedly improve elbow flexion range. However, due to weak flexor muscles, recurrence is common. Therefore, for children over 5 years old who can cooperate with rehabilitation, triceps or pectoralis major transfer for flexion reconstruction is preferred. In some cases, such as those requiring crutch walking or wheelchair use, 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 mobility. Wrist flexion contractures are not only common but often severe (up to 90°) and accompanied by ulnar deviation. Early correction significantly improves upper limb function, with some advocating passive stretching and splinting shortly after birth, alongside thumb and finger deformity correction. For fixed wrist flexion contractures, serial casting yields good results. However, if wrist extensor weakness exists, recurrence is likely; early flexor carpi ulnaris transfer for extensor reconstruction may be considered. Williams recommends intramedullary nail fixation after age 6 to stabilize the wrist, fixing the metacarpophalangeal joint at 5° flexion with nails in the third metacarpal and distal radius until skeletal maturity, followed by wedge resection and cast fusion. Tachdjian employs dorsal wedge osteotomy of the distal radius/ulna for severe wrist flexion stiffness, correcting deformity while relatively lengthening flexor muscles and soft tissues. Forearm pronation contractures are satisfactorily corrected by pronator teres release or transfer to restore supination. Thumb adduction-flexion deformities often result from hypoplasia or absence of the extensor pollicis longus, brevis, and abductor muscles, leading to adductor pollicis, purlicue soft tissue, and interphalangeal joint contractures that severely impair opposition and grip. Passive stretching and splinting are used in infancy, while purlicue plasty, adductor release, and extensor pollicis lengthening or transfer improve function in early childhood. Finger flexion contractures, though common, are usually mild. Early passive stretching and nighttime splinting prevent progression. Severe cases require superficial flexor and collateral ligament release, with temporary K-wire fixation. If dorsal release improves extension but induces wrist flexion, fractional lengthening of the flexor digitorum profundus/superficialis at the musculotendinous junction is performed. Postoperative casting or long-term nighttime splinting prevents or delays recurrence.

bubble_chart Differentiation

Patients with typical signs, such as limb muscle atrophy and symmetrical joint contractures but 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. Nevertheless, the hand and foot deformities in this type of patient are also mostly symmetrically distributed, which is a characteristic of the disease. Additionally, laboratory tests often show no abnormalities.