Anatomic points within the body are projected outside the body through the use of extenders. Bridges may be used to keep the extenders parallel to each other to provide a spatial transformation of the anatomic points to projected points outside the body. The projected points may then be used for measurement, or to facilitate the selection or configuration of an implant that is to be positioned proximate the anatomic points. Such an implant may be a rod for a posterior spinal fusion system. Pedicle screws may be implanted into pedicles of the spine, and may then serve as anchors for the extenders. The extenders may have rod interfaces that receive the rod in a manner that mimics the geometry of the pedicle screws so that the contoured rod will properly fit into engagement with the pedicle screws.
