Design of Compliant Three-Dimensional Printed Surgical End-Effectors for Robotic Lumbar Discectomy

In this paper, the design of compliant three-dimensional (3D) printed surgical end-effectors for robotic lumbar discectomy is presented. Discectomy is the surgery to remove the herniated disk material that is pressing on a nerve root or spinal cord. This surgery is performed to relieve pain or numbness caused by the pressure on the nerve. The limited workspace of the spine (<27 cm³) results in challenging design requirements for surgical instruments. We propose a new cannula-based robotic lumbar discectomy procedure that can accommodate multiple articulated tools in the workspace at the same time and can be controlled teleoperatively by the surgeon. We present designs for two instruments for this proposed system: an articulated nerve retractor and an articulated grasper. The end-effectors of each are 3D printed with multiple materials, with flexible links acting as joints of the mechanism. These flexible links are actuated by cables which provide sufficient articulation and manipulation forces in the surgical workspace. The end-effector's articulated flexible joint kinematics is modeled and tested for range of motion capabilities. The retraction forces for the nerve retractor and the grasping force for the grasper are also experimentally tested and verified to meet all the design requirements. Additionally, fatigue testing of the flexible joint is presented and teleoperated control for the instruments is demonstrated. Finally, conceptual designs for new actuation systems are presented that will enable feasible surgical operations with the enhanced attributes of the designed end-effectors.