US Patent 8216241 Instruments and methods for manipulating a spinal fixation element

An instrument for manipulating a spinal fixation element relative to a bone anchor includes a bone anchor grasping mechanism, a first adjustment mechanism, and a second adjustment mechanism. The bone anchor grasping mechanism includes a first arm having a distal end configured to engage an opening provided in the bone anchor. The first adjustment mechanism includes a second arm pivotally connected to the first arm. The second arm has a distal end configured to engage an opening provided in the bone anchor and is operable to adjust a spinal fixation element in a first direction upon pivoting relative to the first arm. The second adjustment mechanism is removably and replaceably coupled to the bone anchor grasping mechanism and is movable relative to the bone anchor grasping mechanism to adjust the spinal fixation element in a second direction, perpendicular to the first direction, relative to the bone anchor.