Surgical and medical devices and instruments for treatment of the spine, and for nerve surveillance, guidance and monitoring; namely, cannulae, bone blocks, bone screws, instruments for bone fixation and spacing, prosthetic intervertebral discs, surgical implants comprising artificial material, implant anchorages, instruments for insertion and extraction of all the forgoing, and nerve surveillance systems comprising cannulae, obturators, electrodes, sensors, monitors, cabling, and computer ha...