The scaphotrapezio-trapezoidal joint. Part 2: A kinematic study

Kinematics of the scaphotrapezio-trapezoidal joint during wrist flexion/ext ension motion (FEM) and radial/ulnar deviation (RUD) was investigated using a 3-dimensional dynamic motion analysis system. The scaphoid/trapezoid mot ion was found to be a rotational motion obliquely oriented relative to the sagittal plane of the wrist and described in an ulnoflexion/radial extensio n motion plane in both FEM and RUD of the wrist. The axis of rotation of th e scaphoid/trapezoid motion during both FEM and RUD wrist motions was essen tially the same and runs through the radiopalmar aspect of the distal scaph oid and the waist of the capitate. Motion analysis also revealed that the t rapezium-trapezoid and trapezoid-capitate joints are essentially immobile. Hence, the scaphotrapezio-trapezoidal motion is considered to be a single d egree of freedom that is essentially the same in both FEM and RUD of the wr ist. (J Hand Surg 2000;25A:911-920. Copyright (C) 2000 by the American Soci ety for Surgery of the Hand.).