The improvement is a spinal instrument (preferably, a bone screw driver) having a flexible shaft comprising a plurality of interlocking segments carried on a malleable core rod. The flexible shaft allows a screwdriver handle to be perfectly in-line with the cage inserter if desired, while still taking advantage of the tactile feel and torque transmission of the flex segment in its bent position. Accordingly, a surgeon can limit the amount of retraction and keep the driver handle close to the inserter without having to overcome the forces of the flexible segments natural straight configuration.
