What causes coned epiphyses on the hand radiograph?
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Answer:
Coned epiphyses are epiphyses with a central cone-shaped projection that invaginates into a correspondingly cupped metaphysis, most readily assessed in the middle phalanges on a hand radiograph. They lead to premature fusion, shortening of the affected phalanx and, when many are involved, brachydactyly. The classic association is with the trichorhinophalangeal syndromes (TRPS I and II), where they are highly sensitive, and with cartilage-hair hypoplasia; other causes include acromicric dysplasia, conorenal (Mainzer-Saldino) dysplasia, Ellis-van Creveld syndrome, SOFT syndrome and several other skeletal dysplasias, as well as acquired causes such as trauma, infection, frostbite, sickle cell disease and juvenile idiopathic arthritis. Isolated coned epiphyses also occur as an incidental finding in normal children, so the diagnosis rests on the number, distribution and morphology rather than on their mere presence. Giedion classified the shapes into numbered types, of which type 12 and the milder 12A in the middle phalanges are the ones most associated with the trichorhinophalangeal syndromes.
Why is it called so?
The epiphysis is shaped like a cone whose apex points into the metaphysis, rather than the normal flat or gently convex disc.
Pathophysiology
Growth in a tubular bone depends on an orderly, evenly distributed physeal plate. If the central portion of the physis fuses or is damaged before the periphery, the epiphysis continues to grow only around its rim while its centre is tethered, so the ossification centre is drawn into a cone that presses into the metaphysis, which moulds into a matching cup. In the trichorhinophalangeal syndromes this reflects a genetically determined disturbance of chondrocyte differentiation from TRPS1 haploinsufficiency; in acquired cases it reflects focal physeal injury from ischaemia, infection, inflammation or trauma. Once the cone is established the physis closes prematurely and the bone ends up short.
Alternative names: Cone-shaped epiphyses, cone epiphysis
Other associated named signs: Brachydactyly, ivory epiphyses, Madelung deformity, and the bullet-shaped phalanges of the mucopolysaccharidoses
References
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