KINEMATICS OF THE DISTAL RADIOULNAR JOINT IN RHEUMATOID-ARTHRITIS - AN IN-VIVO STUDY USING CENTRODE ANALYSIS

The kinematics of the distal radioulnar joint were examined using the method of centrode analysis in vivo. A group of normal subjects was st udied along with a group of rheumatoid arthritis patients who had dist al radioulnar joint involvement. Serial computed tomographic scans wer e obtained through the distal radioulnar joint of nine subjects (10 wr ists) in varying degrees of pronation and supination. For normal subje cts, the movement that occurs in a stable distal radioulnar joint is n ot erratic and the center of rotation lies within a well-defined area. When subjects with rheumatoid arthritis were analyzed, it was determi ned that early in the disease process bone erosions may occur in the s igmoid notch of the distal radius. When the joint contour in this regi on is maintained, the kinematics are not markedly altered. Erosion inv olving the dorsal border of the sigmoid notch of the radius is associa ted with subluxation of the distal radioulnar joint. The ulna becomes dorsally positioned relative to the radius, and significant alteration in the kinematics of the distal radioulnar joint occurs.