Synostosis

Radioulnar synostosis involves the proximal ends of the radius and ulna, either as a true radioulnar synostosis or as a variant form. In the former the radius and ulna are fused smoothly at their proximal borders about 26 cm; in the latter fusion occurs just distal to the proximal radial epiphysis and is associated with congenital dislocation of the radial head. Both types lead to interference with normal forearm supination.

Other anomalies that may accompany radioulnar synostosis are clubfoot, developmental dysplasia of the hip DDH , knee anomalies, hypoplasia of the thumb, carpal coalition, symphalangism and Madelungs deformity. Similarly, radioulnar synostosis may be a finding in patients with arthrogryposis, hereditary multiple exostoses, acrocephalopolysyndactyly, acrocephalosyndactyly, Holt Oram syndrome, mandibulofacial dysostosis, Nievergelt Pearlman syndrome, Klinefelters syndrome and other chromosomal aberrations.

Synostosis involving the ribs may occur either as an isolated phenomenon or in association with abnormalities of spinal segmentation or the basal cell naevus syndrome (Gorlins syndrome).

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