Safety analysis and control of a robotic spinal surgical system

Screw path drilling is one of the most common and high-risk operations in many kinds of orthopedic surgery, especially in spinal surgeries. During spinal surgery, the bone screws are inserted into the vertebral body from the narrow vertebral pedicles. Any failures in this process will hurt important vessels and nerves of the patient. In this paper two aspects of the safety issues with using the Robotic Spinal Surgery System (RSSS) are analyzed: movement control and real-time operation control. For the safety motion control of the RSSS, two modes are developed: the cooperative control mode for positioning and the fine adjustment mode for precisely adjusting orientation. An automatic calibration algorithm for force/torque sensors is proposed to eliminate gravity effects. Guidance Virtual Fixtures (GVFs) and Forbidden Region Virtual Fixtures (FRVFs) are used to limit the movement of the RSSS. Damping Region Virtual Fixtures (DRVFs) are proposed to prevent the RSSS from crossing the constraint surface and harming the patient’s body. In the path drilling process, a state recognition algorithm is proposed to simulate the feeling in the hand of the surgeon during surgery. Based on force feature extraction and state recognition algorithm, 5 states in the drilling process are recognized, and the control point, which is the stop point of drilling, is found. Experiments are carried out to verify the DRVFs effects in the motion control of RSSS, the state recognition and safety control of the pedicle drilling.