achondroplasia
most common type of short limbed dwarfism; caused by defect in
enchondral bone formation => shortening of tubular bones with
normal shaft caliber
- hereditary: auto-dominant, > 90% sporadic
x-ray features:
- short extremities and ribs v. trunk length
- "ball-in-socket" epiphyses
- pelvis:
squared iliac wings and narrow
sacrosciatic notch ("champagne glass")
- hands: fingers widely opposed and equal length
("trident hands")
- skull: enlarged vault and mandible, small f. magnum
- spine:
- narrow AP diameter with concave posterior
surface and spinal canal only
1/2 normal depth
- decreased lumbar interpediculate distance
- hypoplastic ("bullet nose") T-L vertebrae
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© 2002, C.E. Kahn, Jr.
2002-04-18