Nonprogressive congenital disorder involving multiple rigid joints (usually symmetric) leading to severe limitation in motion
Epidemiology
incidence 1:3000 live births
Mechanism
symmetry of contractures due to immobilization in utero
neurogenic (90%)
myopathic (10%)
Pathophysiology
exact mechanism unknown
some mothers have serum antibodies inhibiting the fetal acetylcholine receptors leading to a decreased number of anterior horn cells
Associated conditions
orthopaedic manifestations
upper extremity deformity (see below)
teratologic hip subluxation and dislocation
knee contractures
foot conditions
clubfoot
vertical talus
neuromuscular C-shaped scoliosis (33%)
fractures (25%)
Prognosis
nonambulatory (25%)
Classification
Type
Characteristics
Type I
Single localized deformity (e.g., forearm pronation)
Type II
Full expression (absence of shoulder muscles, thin limbs, elbows extended, wrists flexed and ulnarly deviated, intrinsic plus deformity of hands, adducted thumbs, no flexion creases)
Type III
Full expression (type II) with polydactyly and involvement of non-neuromuscular systems
Presentation
Physical exam
inspection & palpation
shoulders adducted and internally rotated (absense of shoulder muscles)
elbows extended (no flexion creases)
wrists flexed and ulnarly deviated
hands with intrinsic plus deformity
thumb adducted
hips flexed, abducted, and externally rotated
subluxation or teratologic dislocation common
knees extended (classical), most of the time flexed
clubfeet
normal intelligence, facies, sensation, and viscera
range of motion
severely limited usually involving all four extremities
Studies
Perform at 3-4 months of age
neurologic studies
enzyme tests
muscle biopsies
Upper Extremity Deformity
Treatment
goals
allow optimal function to increase ability to drive an electric chair and use computer assisted devices
one elbow in extension for positioning and perianal care and one elbow in flexion for feeding