Offset quadrangular clamp
The most common reduction maneuver of the posterior column is the use of the quadrangular clamp applied through the second window.
This clamp is applied with the short arm over the pelvic brim, and the second deep arm applied to the displaced posterior column along the quadrilateral surface.
The vessels are displaced medially to allow clamp placement. Care must be taken to avoid excessive pressure on the vessels by the clamp or force of retraction.