Spine-kinematics with constraint guidance for robot supported MIS-instruments

Feedback of interaction forces/torques in robot supported minimally invasive surgery (MIRS) meanwhile is a widely accepted advantage. To avoid parasitic effects on the according force/torque sensor, e. g. due to friction in the trocar, a sensor integration as distal as possible is advisable. Since common sensor principles are based on wire or fibre connection and since an axisymmetrical instrument´s distal end has to be actuated in at least one additional degree of freedom (DoF) for full dexterity inside the patient, cable (or fibre) break is a serious problem. A constraint guided spine-kinematics without rotatory DoF at its distal end is proposed to reduce the danger of cable (or fibre) break due to a curved flection instead of a sharply bending joint. The properties of a constraint spine-kinematics with one DoF adapted to the special requests of an in-house developed MIRS-system is presented, verification data acquired in a specially developed test bed are shown. The results seem suitable for MIRS applications and for a progress towards a 2 DoF solution with the presented constraint principle.