Kinematic analysis of relative motion within the proximal carpal row.

The motions of the scaphoid and triquetrum relative to the lunate have been studied on cadaver specimens. The helical axis concept was applied. The wrist motions performed were flexion-extension and radial-ulnar deviation. The results showed increased relative motion of the scaphoid towards terminal extension, and to a lesser amount in the case of the triquetrum, towards terminal flexion. The lunate might be considered as a keystone in the proximal carpal row when wrist stability is considered. It is doubly intercalated: longitudinally and transversely. Wrist ligaments co-ordinate the positioning of the bones in the mid-range of carpal motions, and restrict further motion in extreme positions of the wrist joint.