Three-dimensional kinematic analysis of the second through fifth carpometacarpal joints.

The kinematics of the 2nd through 5th carpometacarpal (CMC) joints was investigated by using a 3-dimensional dynamic motion analysis system to delineate flexion-extension motion, radial-ulnar deviation, and pronation-supination motion. Analysis of the axes of rotation revealed that the axes of rotation for flexion-extension motion are located within the base of each respective metacarpal bone. The axis of rotation for radial-ulnar deviation passes through the distal carpal bone of each CMC joint except in the 3rd CMC joint where the axis of rotation is located within the base of the 3rd metacarpal. The axis of rotation for pronation-supination motion passes through the base of the respective metacarpal except in the 3rd CMC joint where it is located within the hamate. The overall flexion-extension motions of the 2nd and 3rd carpometacarpal (CMC) joints were found to be more limited than those of the 4th and 5th CMC joints (11 degrees, 7 degrees to 20 degrees, 27 degrees, respectively) and even more so in radial-ulnar deviation (2 degrees, 4 degrees to 7 degrees, 13 degrees, respectively) and pronation-supination motion (5 degrees, 5 degrees to 27 degrees, 22 degrees, respectively). The 5th CMC joint has the greatest overall range of motion with the flexion-extension motion found to be greatly reduced by 40% to 28 degrees when the 4th CMC joint was immobilized. Maximum range of motion in flexion-extension of the 5th CMC joint is dependent on and contributed by the 4th CMC joint motion.