Study of wrist motion in flexion and extension.

During flexion and extension of the wrist, the total range of motion is determined by the radiocarpal and the midcarpal joints. The angular contribution of each carpal row has been differently quantitated by previous investigators. A radiographic investigation of the wrist motion in flexion and extension was undertaken in 55 normal wrists to determine the contribution of the radio--carpal and mid carpal joints. The angular relationships of the radial and carpal components were also analyzed. In neutral position, the lunate and capitate are coaxial with the radius in a small percentage: lunate 11%, capitate 16%. In neutral position, the radio--lunate, lunate--capitate angles neutralize each other in a zig-zag manner in only 11%. During maximum flexion, the motion is 40% radio--carpal and 60% mid carpal. During maximum extension, the motion is 66.5% radiocarpal and 33.5% mid carpal. Functionally the scaphoid belongs to the 1st carpal row in flexion and to the second row in extension.