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An anomaly, consisting of longitudinal segmentation, resulting in forearm shortening with fixed pronation because of radioulnar synostosis.

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First described by G.B. Davenport, in 1924.

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Usually sporadic; however, autosomal dominant with variable expression has also been suggested.

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Can occur as the only abnormality. Often associated with other chromosomal constellation abnormalities including XXXY syndrome and 48,XYYY syndrome. Upper limb bud arises at 26 days of age. The defect in longitudinal segmentation occurs at the seventh week of development when, for a time, the proximal radius and ulna are united and share a common perichondrium. It is possible that abnormal genetic or teratogenic factors operating at this time would interfere with proximal radioulnar joint morphogenesis. Radioulnar synostosis occurs bilaterally in 60% of cases.

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Clinically evocated by family history and the presence of an average fixed flexion contracture, forearm shortening, hypermobility of wrist, and fixed pronation. Confirm by radiological features showing synostosis from proximal fibrous union to total synostosis of radius and ulna. Chromosomal study normal in isolated radioulnar synostosis.

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There are two types described. In type I, there is a proximal, smooth fusion of 2 to 6 cm (0.8 to 2.4 inches) between radius and ulnar, and absent radial head. In type II, there is a fusion just distal to the proximal radial epiphysis in association with congenital dislocation of the radial head. Both types result in a limitation of pronation and supination of the forearm, and in type II, there is also limited extension of the elbow. Common associated abnormalities are mental retardation, hypotonia, and abnormal facies.

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Document function of limbs.

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None in isolated radioulnar synostosis. Proper care should be taken in positioning limb. Regional anesthesia is not contraindicated; however, radial nerve blockade at the elbow is best avoided, particularly in type II.

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There are no specific implications for this condition.

Bauer M, Jonsson K: Congenital radioulnar synostosis. Scand J Plast Reconst Surg 22:251, 1988.  [PubMed: 3252456]
Davenport CB, Taylor HL, Nelson LA: Radio-ulnar synostosis. Arch Surg 8:705, 1924.

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