Achondroplasia

  • Etiology: congenital defect in enchondral bone formation (bone lengthening)
  • Imaging: flared iliac wings, champagne glass pelvis, trident pelvis, trident hand, progressive interpediculate distance narrowing at lower lumbar vertebrae, pedicles are short leading to spinal stenosis, posterior scalloping of vertebral bodies, anterior beaking of vertebral bodies, long bones short + flared, brachycephaly, frontal bossing, small face bones due to dysplastic skull bone, normal cranium, keyhole foramen magnum, constricted jugular foramina causing intracranial venous hypertension + communicating hydrocephalus, prominent emissary veins as collaterals
  • Clinical: rhizomelic dwarfism, most common dwarf

Radiology Cases of Achondroplasia

Radiograph of trident hand in achondroplasia
AP radiograph of the hand shows diffuse shortening of the phalanges and metacarpals, giving the hand the appearance of a trident. There is also metaphyseal flaring of the distal radius and ulna.
Radiograph of rhizomelic shortening in achondroplasia
AP radiograph of the upper extremity shows proximal (rhizomelic) shortening of the humerus along with flaring of the distal metaphysis of the radius and ulna.
Radiograph of interpedicular narrowing and spinal stenosis in achondroplasia
AP radiograph of the lumbar spine (left) shows progressive narrowing of the distance between the pedicles descending through the lumbar spine (interpediculate narrowing). The lateral radiograph of the lumbar spine (right) shows shortened pedicles leading to narrowing of the anterior-posterior diameter of the spinal canal (spinal stenosis) and that the vertebral bodies have some anterior wedging and posterior scalloping.
Radiograph of champagne glass pelvis of achrondroplasia
AP radiograph of the pelvis shows squaring of the iliac bones, flattening of the acetabulae, and small sacroiliac notches bilaterally, leading to a champagne glass appearance to the pelvic inlet.