This articulation of the metacarpal bone of the thumb is luxated either thenad or anconad of the os trapezium; when thenad, there is a prominence in the palm of the hand, the finger is extended anconad, and cannot be inflected thenad; when luxated anconad, there is a projection on the anconal aspect of the wrist, the thumb is inflected thenad, and cannot be extended.
Source: wiktionary