What causes a rachitic rosary on the chest radiograph?
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Answer:
A rachitic rosary is bulbous, nodular expansion of the anterior rib ends at the costochondral junctions, producing a row of palpable and radiographically visible beads down each side of the sternum. It is a classic sign of rickets, in which the costochondral junction behaves like any other growth plate and undergoes the same changes. Radiographically the rib ends are widened, cupped and indistinct, matching the metaphyseal changes elsewhere. It should be read with the rest of the skeletal survey of rickets: metaphyseal fraying, splaying and cupping, widening of the growth plate, coarse trabeculation and generalised osteopenia, bowing of the long bones, Looser zones (pseudofractures), frontal bossing, craniotabes and the Harrison sulcus. The scorbutic rosary of scurvy produces a similar row of beads but the junction is more angular with a sharper step-off, and it is accompanied by the quite different findings of the white line of Frankel, the Wimberger ring sign, Pelkan spurs and subperiosteal haemorrhage.
Why is it called so?
The row of rounded swellings along the costochondral junctions resembles a string of rosary beads.
Pathophysiology
In rickets, deficient vitamin D, calcium or phosphate prevents mineralisation of the newly formed osteoid at every growth plate. At the costochondral junction the hypertrophic chondrocyte zone continues to proliferate but the provisional zone of calcification fails to mineralise, so unmineralised cartilage and osteoid accumulate and the junction widens and expands laterally. The result is a bulbous, mechanically soft rib end that is both palpable and radiographically enlarged. The same failure of mineralisation at the long bone metaphyses produces the fraying, cupping and splaying, and the softened diaphyses bow under load.
Alternative names: Rachitic beads, rickety rosary
Other associated named signs: Scorbutic rosary, Harrison sulcus, Looser zones, metaphyseal fraying and cupping, and the Wimberger ring sign of scurvy
References
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