System for measuring the displacements of a vertebral column

A system for measuring the displacements of a vertebral column having a segment comprising at least one vertebra having a body delimited by an upper vertebral end plate and a lower vertebral end plate, and each vertebra in the segment having a location marker associated, attached thereto and providing a location system with an orientation of the location marker, the system including a localizer configured to detect the initial orientations of the location markers, and a microprocessor configured to determine, for each vertebra, an initial orientation of a vertebral plane parallel to at least one end plate of the vertebra, and to determine the current orientation of the vertebral plane of the vertebra from the current orientation of the location marker associated and the geometrical transformation associated with the vertebra.