Surgical system for cutting an anatomical structure of a patient according to a target plane defined in a coordinate system of the anatomical structure, comprising: (i) a robotic device comprising: - a cutting tool configured to cut the anatomical structure according to a cutting plane, - an actuation unit comprising from three to five motorized degrees of freedom, said actuation unit comprising at least one portion having a parallel architecture comprising a base and a platform selectively orientable relative to the base according to at least two of said motorized degrees of freedom, for adjusting a position and orientation of the cutting plane relative to the target plane, - a planar mechanism connecting a terminal part of the actuation unit to the cutting tool, the planar mechanism being configured to constrain the cutting tool to move only inside a plane, with at least two degrees of freedom, (ii) a passive articulated lockable holding arm supporting the actuation unit, (iii) a tracking unit configured to determine in real time the pose of the cutting plane with respect to the coordinate system of the anatomical structure, (iv) a control unit configured to determine the pose of the cutting plane with respect to the target plane, to detect whether the cutting plane can be aligned with one target plane without changing the pose of the actuation unit, the control unit being further configured to, if the cutting plane cannot be aligned with the target plane, compute indication to a user to reposition the actuation unit with respect to the anatomical structure and, if the cutting plane can be aligned with the target plane, control the actuation unit so as to bring the cutting plane into alignment with the target plane, (v) a user interface coupled to the control unit, configured to indicate directions to a user to position the actuation unit with respect to the anatomical structure according to a pose allowing aligning the cutting plane with the target plane. (i) a robotic device comprising: - a cutting tool configured to cut the anatomical structure according to a cutting plane, - an actuation unit comprising from three to five motorized degrees of freedom, said actuation unit comprising at least one portion having a parallel architecture comprising a base and a platform selectively orientable relative to the base according to at least two of said motorized degrees of freedom, for adjusting a position and orientation of the cutting plane relative to the target plane, - a planar mechanism connecting a terminal part of the actuation unit to the cutting tool, the planar mechanism being configured to constrain the cutting tool to move only inside a plane, with at least two degrees of freedom, - a cutting tool configured to cut the anatomical structure according to a cutting plane, - an actuation unit comprising from three to five motorized degrees of freedom, said actuation unit comprising at least one portion having a parallel architecture comprising a base and a platform selectively orientable relative to the base according to at least two of said motorized degrees of freedom, for adjusting a position and orientation of the cutting plane relative to the target plane, - a planar mechanism connecting a terminal part of the actuation unit to the cutting tool, the planar mechanism being configured to constrain the cutting tool to move only inside a plane, with at least two degrees of freedom, (ii) a passive articulated lockable holding arm supporting the actuation unit, (iii) a tracking unit configured to determine in real time the pose of the cutting plane with respect to the coordinate system of the anatomical structure, (iv) a control unit configured to determine the pose of the cutting plane with respect to the target plane, to detect whether the cutting plane can be aligned with one target plane without changing the pose of the actuation unit, the control unit being further configured to, if the cutting plane cannot be aligned with the target plane, compute indication to a user to reposition the actuation unit with respect to the anatomical structure and, if the cutting plane can be aligned with the target plane, control the actuation unit so as to bring the cutting plane into alignment with the target plane, (v) a user interface coupled to the control unit, configured to indicate directions to a user to position the actuation unit with respect to the anatomical structure according to a pose allowing aligning the cutting plane with the target plane.