An apparatus for measuring a distance between first and second implanted bone anchors includes a caliper body and first and second caliper arms. The caliper body has a first longitudinal axis. The first caliper arm is slidably coupled to the caliper body and has a second longitudinal axis. The second caliper arm is rotatably coupled to the caliper body and has a third longitudinal axis. The first, second and third longitudinal axes define a plane. The second caliper arm is rotatable within the plane between a first position and a second position.
