[Movements of the pisiform and triquetrum bones and their significance for kinematics of the ulnar wrist].

The purpose of this study is to investigate carpal kinematics with respect to the pisotriquetral joint, before and after pisi-form excision. Five cadaver-hands were studied and a custom-designed plexi-glass-fixation device was used to standardize the wrists for exact passive movements in flexion and extension as well as in ulnar and radial abduction. Five sets of motion were registered before and after excision of the pisiform. Motion of the triquetrum and pisiform were studied by 3D-Motion Analysing Software System (peak 54). The results indicated that the excision of the pisiform does have an influence on the kinematics of the wrist. The movement of the triquetrum was increased after removal of the pisiform. Although the differences in measurement were only a few of millimetres and degrees, we know from the dorsal and palmar intercalated segment instabilities that even minor instabilities can act as a predisposing factor for arthrosis. Therefore, the excision of pisiform must be carefully considered. The common joint between the triquetrum and pisiform supports and indicates relation of their movements. However, the correlation for flexion/extension and radial deviation was high, an obvious correlation of the movements for ulnar deviation was not verifiable.