[Biomechanics of the carpus and wrist joint].

During the last decade the classical idea of the rigid carpal block was abandoned in favour of the "carpus of variable geometry". The basic advantage of this new concept is the presumption that the proximal carpal row can be regarded as an intercalated structure, and the idea of the "useful distance" between the forearm socket and the distal carpal row. This "useful distance" can be filled up by elementary movement of the bones of the first carpal row. This directly leads to the concept of the "internal coherence of the carpus" and "variable geometry". The internal components of associated movements in the carpal region are described. Finally, the self-blocking system, the associated movement of the bones of the first carpal row caused by the interosseous ligaments, and the new definition of carpal instability are also discussed.