A, Taleisnik’s concept of central (flexion-extension) column involves entire distal row and lunate: scaphoid (S) is lateral (mobile) column, and triquetrum (Tq) is rotary medial column. B, Lichtman’s ring concept of carpal kinematics: proximal and distal rows are semirigid posts stabilized by interosseous ligaments; normal controlled mobility occurs at scaphotrapezial and triquetrohamate joints. Any break in ring, either bony or ligamentous (arrows), can produce dorsal intercalated segmental instability or volar intercalated segmental instability deformity.