Achondroplasia is the most common congenital dwarfism characterized by shortening of the long bones, especially the proximal ones, leading to an abnormal gait. The hands have a distinctive trident appearance caused by widening between the third and fourth digits. It results from a failure of normal cartilage growth at the growth plates of bones.

1. Achondroplasia
Term used by Parrot
Synonyms are Chondrodystrophia fetalis, chondrodystrophic dwarfism,
and micromelia.
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2. •Most common congenital dwarfism
•The long bones are markedly shortened,
especially the more proximal ones (rhizomelia).
•The upper extremity is affected more than the
lower.
•The cranium is large, with a prominent
forehead and depressed nasal bridge.
•The base of the skull is constricted, and the
foramen magnum is small
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3. •A characteristic rolling gait is caused by
the posterior tilt of the pelvis and
posterior angulation of the hip joints
•The characteristic trident hand is
caused by a widening of the space
between the third and fourth digits
and the inability to approximate them
in extension
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4. Pathology
Failure of normal
enchondral cartilage
growth at the physis
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5. Radiological Features
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6. Splayed and cupped metaphysis
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7. Short thick tubular bones
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8. Trident Hand
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9. Increased disc height and bullet
shaped vertebrae
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10. Short and thick
pedicles contributing
to lumbar canal
stenosis with
posterior vertebral
body scalloping
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11. Differential Diagnosis
•Trisomy
•Mucopolysaccharidosis
•Spondyloepiphyseal dysplasia
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