Pretest

Background and Diagnosis

Arthrogryposis multiplex congenita is a nonprogressive disease that consists of two or more different joint contractures present at birth. There are more than 150 different conditions that are classified under the term arthrogryposis. Causes of arthrogryposis may include abnormalities of muscle, nerve, connective tissue, or limitation of movement in utero. The majority of this tutorial will focus on the most common form of arthrogryposis, amyoplasia. Other disorders in the arthrogrypotic syndromes include Larson’s syndrome, distal arthrogryposis syndrome, and multiple pterygium syndrome.

In 1841, Adolf Wilhelm Otto named the disease congenital myodystrophy. He described the patient as a "human wonder with curved limbs." In 1923, Stern coined the term arthrogryposis multiplex congenita. In 1983, Hall and colleagues named the most common type of the disease amyoplasia.

Amyoplasia consists of multiple joint contractures, which are symmetrical in positioning of the limbs. The etiology does not have a genetic basis but is sporadic in nature. There have been reports of epidemics in the 1960s in areas of eastern Europe and Great Britain. There seems to be an association with a decrease of anterior horn cells and other neural elements of the spinal cord. There is also a questionable relationship to oligohydramnios.

Some of the conditions commonly listed among the arthrogrypotic syndromes include the following:

• Larson’s syndrome is similar to arthrogryposis but with less rigidity. It is mostly associated with multiple joint dislocations such as congenital knee dislocations. Larson’s syndrome also involves abnormal (flattened) facies and congenital vertical talus, neither of which is present in amyoplasia. This syndrome may also involve scoliosis and cervical kyphosis.
• Distal arthrogryposis syndrome, which is an autosomal dominant disorder, predominantly affects the hands and feet. Clubfoot and vertical talus are common findings with distal arthrogryposis.
• Multiple pterygium syndrome, an autosomal dominant disorder, involves cutaneous flexor surface webbing (knee and elbow), congenital vertical talus, and scoliosis. The vascular bundles run within the web areas away from the joint surfaces. This makes release of the contractures and webs extremely difficult.

Clinical Features

A prenatal ultrasound with absence of fetal movement and oligohydramnios may be indicative of amyoplasia. Patients who present with amyoplasia have certain characteristic criteria. The patient will have normal intelligence, no visceral abnormalities, no dysmorphic facies, and no family history of the condition. Patients with amyoplasia patients have characteristic limb positions. The upper extremities will have the shoulders in adduction and internal rotation, the elbows in extension, the wrists in flexion and ulnar deviation, and the fingers flexed clutching the thumb. The lower extremities will have teratologic hip dislocations. The hips can be in flexion, abduction, or external rotation. The knees are usually in extension, although flexion is also possible. Patients may also have a clubfoot deformity.

Amyoplasia is a nonprogressive disease present at birth. Patients have normal sensation. The limbs are featureless and tubular with a lack of normal skin creases, but deep dimples may be present over the joints. It is a pain-free condition with a firm elastic block to movement. Two-thirds of patients have all four limbs equally involved. One-third of patients have predominately lower limbs affected. There tends to be more rigidity and increased severity in the distal portions of the limbs. There may be unilateral or bilateral dislocation of the hips. A characteristic C-shaped scoliotic curve may be present in up to one-third of patients with amyoplasia. Feeding difficulties can result from amyoplasia secondary to a stiff jaw and immobile tongue. At 5 years of age, 85% of patients with amyoplasia are ambulatory and independent.

The diagnosis of amyoplasia is based on clinical findings. Early radiographic studies of patients with amyoplasia only show loss of subcutaneous fat and muscle. The joints are normal until adaptive changes occur or unless dislocations are present. Histological studies, such as muscle biopsies, are not impressive. There is small muscle mass with fibrosis and fat between muscle fibers.

Treatment

The goals of treatment entail maximizing upper extremity motion for self-care and lower limb alignment and stability for shoe wear, sitting, and ambulation.

Early passive range of motion of all involved joints with physical therapy is beneficial. Although improvement in range of motion is minimal, most success with physical therapy is achieved if started before 1 year of age. Twenty-five percent of patients born with amyoplasia will have fractures of some type at birth. This is a result of several factors. First, the joint contractures cause difficulty during birth resulting in neonatal fractures. Second, the skeleton is osteopenic due to decreased loading. Finally, stress is concentrated on the long bones due to the joint contractures, and they may fracture during dressing or other daily care. Therefore, an examination for diaphyseal fractures should be performed before beginning physical therapy in the nursery. If a fracture is present, it should be splinted in a functional position.

If joint surgery is performed before any adaptive intra-articular changes occur, then there are better outcomes. Osteotomies must be performed closer to completion of growth to decrease the rate of recurrence.

When treating the upper extremity in patients with amyoplasia, think about the entire arm and not just individual joints. The goals of upper extremity management are:

• Self-care skills that allow patients to perform feeding and toileting activities.
• Mobility skills that allow patients to push out of a chair and use crutches.

The shoulder joint is often adducted and internally rotated. This position allows for satisfactory function of the upper extremity without surgical intervention. The elbow joint is usually fixed in extension. If there is bilateral elbow contractures, one elbow should be left in extension for positioning and perineal care whereas the other elbow should be placed into flexion for feeding. Osteotomies of the distal humerus may be performed after the first decade of life. Prior to the first decade, elbow capsulotomy and triceps lengthening have shown fair success. Passive flexion to 90° is needed before tendon transfers for active elbow flexion. The thumb is often flexed and adducted into the palm of patients with arthrogryposis. The thumb responds to surgery much better than other digits of the hand.

The treatment goals of the lower extremity can be categorized by joint, but the ultimate overall goal is to improve ambulation. Approximately two-thirds of patients with amyoplasia develop hip dysplasia or frank dislocation. Patients with hip dislocations have poor success with closed reduction. Patients with unilateral hip dislocations have poor functional outcomes if left untreated. Treatment options for patients with bilateral hip dislocations are more controversial. If left untreated, patients maintained satisfactory range of motion. Bilateral dislocations did not prevent these patients from walking. Open reduction with the medial approach has demonstrated promising results. If the patient requires mobilization for the knees, these approaches should be performed first to allow flexion and help maintain the hip reduction.

The classic presentation for knee contractures is one of extension, but many patients with amyoplasia present with flexion contractures. Hyperextension contractures respond better than flexion contractures about the knee to physical therapy. Flexion contractures larger than 30° cause poor ambulation as a result of muscle weakness. Prior to 2 years of age, patients should undergo capsulotomy with soft tissue releases. Supracondylar osteotomies allow for significant correction but are associated with recurrence in children secondary to remodeling at a rate of 1° per month and often require repeat procedures.

Foot deformities are common in patients with amyoplasia. The majority of deformities are clubfeet. In patients with amyoplasia, the clubfoot deformity is unresponsive to stretching and casting. Circumferential releases with resection of tendon insertions are necessary, including surgery on the plantar aspect of the foot. These releases should be performed at approximately 1 year of age or later. Talectomy can be performed with fairly good success rates for late recurrence. Once patients reach their late teens, a triple arthrodesis may be the most appropriate option. The goal of correction should be to obtain a stiff plantigrade foot for shoewear and possible ambulation. Vertical talus is not common in amyoplasia. The patient with a vertical talus most likely does not have amyoplasia but may have distal arthrogryposis or multiple pterygium syndrome.

The sequence of lower extremity procedures is to mobilize the knees, treat hip dislocations, and correct clubfoot deformities.

Scoliosis is a common finding in patients with neuromuscular dysfunction. The incidence of scoliosis in arthrogrypotic patients is approximately 50%. Scoliosis in infants with arthrogryposis is a result of contractures and responds to stretching and orthotic bracing. In children and adolescents, the scoliosis may be a result of an anterior horn cell defect occurring in utero. Lumbar and thoracolumbar curves are most typical. Children and adolescents respond poorly to orthoses. Indications for surgical correction of scoliosis are similar to that of other neuromuscular scoliosis.

Bibliography

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Sarwark J, MacEwen GD, Scott CI. Amyoplasia: A common form of arthrogryposis. J Bone Joint Surg. 1990; 72:465-469.

Staheli LT, Hall JH, Jaffe KM, Paholke DO. Arthrogryposis: A Text Atlas. Oxford, United Kingdom: Cambridge University Press; 1998.

Staheli LT, Chew DE, Elliott JS, Mosca VS. Management of hip dislocations in children with arthrogryposis. J Pediatr Orthop. 1987; 7:681-685.

Zimbler S, Craig C. The arthrogrypotic foot: Plan of management and results of treatment. Foot Ankle. 1983; 3:211-219.