A positioning device for placing a prosthesis device in a spinal column of a living mammal, the device including at least one holding means for cooperation with the prosthesis device and for guiding thereof during positioning. The positioning device may also include fixing means for fixation with respect to at least one vertebra, where the fixing means includes locking means, which in a first, free state, allows adjustable movement of the holding device and thereby of the prosthesis device, and in a second, locked state, fixes the holding means and thereby the prosthesis device in a selected position. Embodiments of the disclosure also include Embodiments of the invention also include a system.