Definition

Arthrogryposis multiplex congenita (AMC) is a congenital anomaly in the newborn involving multiple curved joints (see Fig. 674-1 on the Nelson Textbook of Pediatrics website at www.expertconsult.com ). Arthrogryposis is a descriptive term and not an exact diagnosis, as there are as many as 300 possible underlying causes.

Figure 674-1 Arthrogryposis multiplex congenita. A 32-wk premature boy with severe multiple congenital contractures and severe congenital neuropathy.

(From Hosalkar HS, Moroz L, Drummond DS, et al: Neuromuscular disorders of infancy and childhood and arthrogryposis. In Dormans J, editor: Pediatric orthopedics: core knowledge in orthopedics, Philadelphia, 2005, Mosby, pp 454–482.)

The incidence of classic AMC is approximately 1/3,000 live births, and the three main groups include classic AMC, in which the limbs are primarily involved and the muscles are deficient or absent (amyoplasia) (Fig. 674-2); arthrogryposis in association with major neurogenic (brain, spinal cord, anterior horn cell, or peripheral nerve) or myopathic (congenital muscular dystrophy, myopathy, toxic myopathy) dysfunction; and arthrogryposis in association with other major anomalies and specific syndromes such as diastrophic dysplasia and craniocarpotarsal dystrophy (Table 674-1).

Figure 674-2 Child with amyoplasia. In the upper extremity, the shoulders are internally rotated, the elbows are extended, the wrists are flexed and ulnarly deviated, the fingers are stiff, and the thumbs are positioned in the palm. In the lower limbs, the hips may be dislocated, the knees are extended, and the feet have severe equinovarus contractures.

(From Bamshad M, Van Heest AE, Pleasure D: Arthrogryposis: a review and update, J Bone Joint Surg Am 91[Suppl 4]:40–46, 2009.)

Clinical Features

Multiple rigid joint deformities are present with defective muscles and normal sensation. There is rigidity of several joints in each case, resulting from both short tight muscles and capsular contractures. Pterygium may be present on the flexor aspects of contracted joints (Fig. 674-3). There is often an absence or fibrosis of muscles or muscle groups. There is normal intellectual development in most cases. All four limbs are involved in the classic form (AMC), but the condition can also occur in the upper or lower limbs. An autosomal dominant variant called distal arthrogryposis involves the hands and feet with severe deformation but with only minor contractures more proximally; scoliosis is a possible development. To date, 10 different distal arthrogryposes have been described. They are classified according to the proportion of features they share (Table 674-2). In addition to the multiple joint contractures, the lack of skin creases (cylindrical or tubular limbs) and deep dimples over the joints are very characteristic (Fig. 674-4). There is dislocation of joints, most commonly the hip but occasionally the knee; the trunk is rarely affected. Other congenital anomalies such as cryptorchidism, hernias, and gastroschisis can occur.

Figure 674-3 Fixed flexion of the knees in a boy with arthrogryposis multiplex congenita.

(From Hosalkar HS, Moroz L, Drummond DS, et al: Neuromuscular disorders of infancy and childhood and arthrogryposis. In Dormans J, editor: Pediatric orthopedics: core knowledge in orthopedics, Philadelphia, 2005, Mosby, pp 454–482.)

Table 674-2 CURRENT LABELS AND OMIM NUMBERS FOR THE DISTAL ARTHROGRYPOSIS SYNDROMES

Figure 674-4 Characteristic lack of skin creases and tubular limbs.

(From Hosalkar HS, Moroz L, Drummond DS, et al: Neuromuscular disorders of infancy and childhood and arthrogryposis. In Dormans J, editor: Pediatric orthopedics: core knowledge in orthopedics, Philadelphia, 2005, Mosby, pp 454–482.)

Etiology

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