Yoshio Nakashima

A study of bone micro-cutting characteristics using a newly developed advanced bone cutting machine tool for total knee arthroplasty

Bone cutting experiments were conducted on a cadaver using a newly developed machine tool. The effectiveness of the system was evaluated by comparing the planned shape for the mating surface between the femur and an artificial joint with the cutting result. It is desirable to know the machining phenomena and characteristics at the microscale because the material and the tissue structure are anisotropic in both cortical and cancellous bones. In the paper, the influence of the material characteristics on machining is discussed for cortical bone. Pig cortical bone was used in the experiment for visualizing 2-dimensional micro-cutting.

Development of a Computer-Integrated Minimally Invasive Surgical System for Knee Arthroplasty

Recently, the number of robot-assisted orthopaedic systems has been increased. As one of the backgrounds, it is considered that the error between the plan and the result of bone cutting is not constant because of the individual surgeons skill. The authors developed a bone cutting robot which has 7 degrees of freedom. A prototype of the total system for minimally invasive knee arthroplasty, including navigation system, was implemented. In this paper, the detail of the minimally invasive knee arthroplasty system is described, the resection experiment for a cadaver was performed successfully

Optimal control of cutting feed rate in the robotic milling for total knee arthroplasty

For the total knee arthroplasty, we developed the robotic system, such as the cutting feed rate is controlled depending on the hardness of the bone tissue predicted on the basis of the medical image. Since the cutting force is reduced by this system, the displacement of the bone is minimized during the bone cutting process. Therefore it makes a possibility to fix the target bone using “safer” and less-invasive fixation technique.

Bone Cutting Robot with Soft Tissue Collision Avoidance Capability by a Redundant Axis for Minimally Invasive Orthopedic Surgery

Many of the robots developed so far, including our multi-axis bone cutting robot, use an end mill as the cutting tool, and some problems should be solved to apply them to the minimally invasive orthopedic surgery. Minimally invasive surgery makes the incisions smaller, reduces pain and trauma to the body, and enables faster recovery. The smaller incision means a small and narrow opening area. This means the robot attitude for the bone resection is restricted, and it can result in the collision of the tool with the surrounding tissue, the existence of an untouched area and the degradation of the joint position accuracy. This paper proposes a robot mechanism and a toolpath generation technique specialized for bone cutting is expected to resolve these issues.

Development of a bone cutting robot for total knee arthroplasty

In total knee joint replacement, the femur and the tibia must be precisely shaped to ensure that they firmly mate with the artificial joint. The normal procedure is to manually cut the bones using a bone saw and mechanical jigs. A 9-axis bone cutting machine tool has been developed by the authors to increase cutting accuracy and reduce the hospital stay required for recuperation. As developed, the cut plane is determined by a 5 degree-of-freedom mechanism and the femur and tibia are cut by moving two translational and one rotational degrees of freedom, a system that provides a cutter path which avoids cutting the ligament. A preoperative planning system based on CAD/CAM principles and an overview of a system for total knee arthroplasty is also discussed. Experimental results showed the effectiveness of the developed robot and the system.