Wednesday, June 12, 2024

Ulnar Clubhand

Background

Ulnar clubhand is much less common than radial clubhand and is more appropriately referred to as ulnar deficiencies of the forearm. Most cases are sporadic in occurrence, though genetic syndromes are associated with ulnar dysplasia.

Close to 70% of cases of ulnar clubhand are unilateral. A partial rather than complete absence of the ulna is common. Ulnar shortening with radial bowing and abnormal digits is the classic presentation of this condition, and digital anomalies can be found in close to 90% of cases with postaxial absence of ulnar rays.
The fourth and fifth metacarpals, as well as the capitate, lunate, triquetrum, hamate, and pisiform, are absent or deformed.

Synostosis with the humerus is possible when the ulna is present; radiohumeral synostosis can also be present. The radial head is dislocated in close to 50% of cases.

Radial bowing is produced by the tethering effect of the fibrocartilaginous ulnar anlage, which can also tether the carpus, producing limitation of wrist movement. The radiocarpal joint has a fixed ulnar deviation in these cases. In most cases, however, function is very good, and the carpus can be actively centralized. The presence of a thumb makes for a functional hand, unlike the case for radial clubhands.

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