Abstract: A computerized method aiding a surgeon end-user, comprising Providing a light projector configured to project at least one pattern onto spine, Providing 3D video cameras operative, when the spine is in their field of view, to capture 3D video imagery of the spine and pattern; Providing a tool tracker comprising an INS operative to repeatedly compute an output tool-status indication of a current orientation and position of tool used during spine surgery, and a wireless communication module providing data communication between subsystem and a processor including sending the output tool-status indication to the processor, the processor including logic configured to receive the output tool-status indication generated by the tool tracker and the 3D video imagery, and to track vertebra, using the pattern, which is known to the processor, and accordingly to provide feedback to the surgeon.