Champagne glass pelvis | Radiology Signs

Answer:

The champagne glass pelvis is the shape taken by the pelvic inlet when the iliac wings are squared and shortened, the sacrosciatic notches are narrow and deep, and the acetabular roofs are flat and horizontal, so that the inlet is broad above and abruptly tapered below, resembling a champagne coupe. It is a hallmark of achondroplasia, the commonest non-lethal skeletal dysplasia, caused by gain-of-function variants of FGFR3, most often p.Gly380Arg, inherited as an autosomal dominant trait with a high new mutation rate related to advanced paternal age. The pelvic finding should be read as part of the full skeletal pattern: rhizomelic limb shortening with metaphyseal flaring, trident configuration of the hands, progressive caudal narrowing of the lumbar interpediculate distance, short pedicles with posterior vertebral scalloping, a small foramen magnum, and frontal bossing with midface retrusion. The narrow canal and short pedicles are what produce symptomatic spinal stenosis in adulthood, and foramen magnum stenosis is the cause of the infant risk of cervicomedullary compression and sudden death, so imaging surveillance is directed at those two sites. The main differential is hypochondroplasia, which is milder and often lacks the characteristic pelvis, and lethal thanatophoric dysplasia, which shows the same pelvic configuration but with telephone-handle femora and a very narrow thorax.

Why is it called so?

The squared iliac wings and the abruptly narrowed lower inlet give an outline like the bowl and stem of a champagne glass.

Pathophysiology

FGFR3 is a negative regulator of endochondral ossification. The activating variant leaves the receptor constitutively signalling, which suppresses proliferation and differentiation of chondrocytes in the growth plate and shortens all bones that grow by endochondral ossification. Membranous ossification is unaffected, so the calvarium and the iliac apophyses grow normally while the triradiate cartilage and the physes lag, producing squared ilia with a normal-width but vertically short blade, horizontal acetabula and a narrow inlet. The same mechanism at the neurocentral synchondroses causes short pedicles and premature fusion, which narrow the spinal canal, and at the skull base produces the small foramen magnum.

Alternative names: Champagne glass pelvic inlet; tombstone iliac wings

Other associated named signs: Trident hand, the bullet-shaped vertebrae of infancy, and narrowing rather than widening of the interpediculate distance caudally

References

1. Handa A, Grigelioniene G, Nishimura G. Skeletal Dysplasia Families: A Stepwise Approach to Diagnosis. Radiographics. 2023;43(5):e220067. PMID: 37053103.