Figure 3From: A simplified guide ruler from numeric table method in doing rotational osteotomy Use of the ruler in ellipse. Practically, we first make an osteotomy, then measure the long and short axes and mark on the ruler. The chord distance t can be read directly on the ruler at a proposed correction angle. In this example, we mark long and short axes, set the rotation angle = 28°. The chord distance can be read in the ruler directly.Back to article page