Robotic surgical assembly comprising: - a slave manipulator comprising: - an actuator; - at least one pushing device, connected to said actuator - at least one sensor (71, 72) detecting a contact force on said pushing device; - a position sensing system; - a sterile barrier; - at least one control unit configured to receive information about said sensor to control said actuator; - a surgical instrument operated on by said slave manipulator and detachably attached to said slave manipulator and separated from said slave manipulator by said sterile barrier; said surgical instrument further comprising: - a frame; - a link (6; 7; 8; 43) articulating in a joint (14; 17) with respect to said frame; - a tendon, associated to said actuator, having a tendon proximal portion, and a tendon distal portion, secured to said link (6; 7; 8; 43); - at least one transmission device, in contact with said tendon proximal portion, in order to exert a traction action on said tendon; said transmission device being constrained by a coupling device to have a single degree of freedom of motion with respect to said frame; - at least one elastic device attached between said instrument frame and said transmission device; and wherein, whenever said surgical instrument is attached to said slave manipulator: - said at least one pushing device releasably and selectively connects with said transmission device to transmit a pushing action to said transmission device through said sterile barrier; - said at least one sensor (71, 72) detects a contact force between said pushing device and said transmission device; - said at least one elastic device biases said at least one transmission device away from said pushing device, so as to exert a traction action on said tendon. - a slave manipulator comprising: - an actuator; - at least one pushing device, connected to said actuator - at least one sensor (71, 72) detecting a contact force on said pushing device; - a position sensing system; - a sterile barrier; - at least one control unit configured to receive information about said sensor to control said actuator; - a surgical instrument operated on by said slave manipulator and detachably attached to said slave manipulator and separated from said slave manipulator by said sterile barrier; - an actuator; - at least one pushing device, connected to said actuator - at least one sensor (71, 72) detecting a contact force on said pushing device; - a position sensing system; - a sterile barrier; - at least one control unit configured to receive information about said sensor to control said actuator; - a surgical instrument operated on by said slave manipulator and detachably attached to said slave manipulator and separated from said slave manipulator by said sterile barrier; - a frame; - a link (6; 7; 8; 43) articulating in a joint (14; 17) with respect to said frame; - a tendon, associated to said actuator, having a tendon proximal portion, and a tendon distal portion, secured to said link (6; 7; 8; 43); - at least one transmission device, in contact with said tendon proximal portion, in order to exert a traction action on said tendon; said transmission device being constrained by a coupling device to have a single degree of freedom of motion with respect to said frame; - at least one elastic device attached between said instrument frame and said transmission device; - said at least one pushing device releasably and selectively connects with said transmission device to transmit a pushing action to said transmission device through said sterile barrier; - said at least one sensor (71, 72) detects a contact force between said pushing device and said transmission device; - said at least one elastic device biases said at least one transmission device away from said pushing device, so as to exert a traction action on said tendon.