Sagittal computed tomography image of the radiocarpal joint. Point A and C were marked at subchondral fracture margin of lunate facet of distal radius. A circle matching curvature of remaining articular surface of distal radius was traced and passed through point A. First line was drawn from center of circle to point C. The intersection between circle and first line was point B. Step displacement is measured as the distance between points B and C. Gap displacement is measured as the distance between points A and B.