| In the past two decades, computer aided techniques and surgical robots are being widely used in different types of medical applications with accurate visualization, highly precise operation, minimal invasion and low radioactive damage to patients and surgeons. Therefore, computer aided and robotic assisted surgical system form a hot research topic for exploration.;In this research, for orthopedic surgical process, we proposed to set up and develop an integrate solution consisting of a navigation system and a robotic arm with hands-on capabilities. This system will assist the surgeon in the orthopedic surgery, with intramedullary nailing, bone milling and joint replacement operations among others.;In this system, Staubli TX60, designed for use in super-clean environment, was adopted as the assistive robotic arm. We derived the kinematics and inverse kinematics of this robot for real-time control. The robot with surgical tool mounted can be considered as a smart tool that extends surgeon's ability to implement the surgery in cooperative mode with surgeon. In the cooperative control law, the concept of virtual fixture was used to refer to a task dependent aid that guides the user's motion along desired directions while preventing motion in undesired directions or regions of the workspace. This will reduce the tremor and mental load of the user, and increase the quality of the surgical task. When completing this type of task, in which robot works under the admittance mode, the instant velocity of the robot end-effector needs to be calculated in real-time. To comprise real-time capacity and reduce the effect when movement of robot arm encounters the singularity, singularity separation damped reciprocal (SSDR) algorithm is applied as to give better result than that of traditional damped least square (DLS) algorithm.;When drilling bone during orthopedic surgery, the force sensing between drill bit and bone is significant, by which surgeon can decide the depth of penetration into different tissue layers. In our system, ATI force/torque sensor was mounted on the end-effector of the robot arm. When drilling the bone, the force and torque signals were recorded. Applying the real-time wavelet transform, the break-through of different layers could be detected. In vitro porcine femur experiment, we tested different surgical drill bits with different parameters and shapes. Finite element simulation and analysis were introduced to evaluate the design of surgical tool and intra-operative biohazard. In previous finite element simulation research, the bone was considered as elastic material under tiny deformation, by which the simulation was a static deformation process. However, for drilling and other machining processes, the bone shows elasto-plastic characteristics against the elastic model for the static process. Using finite element method, simulation of bone drilling process could predict the biomechanical performance on the bone surface and different drill bits. The bone biomechanical parameters for elastic model consist of Young's modulus, Poisson's ratio, and thermal conductivity. For plastic model, the flow stress curve describes the biomechanics of the compact bone. In the simulation, the elasto-plastic curve of the bone was divided into elastic and plastic region according to the strain range. The stress distribution was calculated and displayed on the 3D model. To verify the results of FEA, drilling force and mean stress distribution were evaluated. In vitro experiment, force signal of drilling on fresh porcine femur was recorded for comparison with the results of FEA. The magnitude and variation tendency of drilling force from the FEA are in accordance with those of experimental results. The novel 3D dynamic visualization of drilling process could assist the surgeon by providing visual force feedback and prediction for the surgery process. |
