Robotic solution for orthopedic surgery.

In orthopedic surgery, the accuracy of internal fixation is related to the success of the procedure. In the past, orthopedic surgeons usually placed screws freehand according to anatomical landmarks or fluoroscopy images. Although there are many surgical techniques for inserting screws freehand, the accuracy of freehand screw placement is not high enough, and the results can be unstable. The accuracy of freehand screw placement reported in the literature varies greatly. Particularly in the spine, with its unique anatomy and important adjacent tissues, inaccurate screw placement may lead to serious complications, such as nerve or vessel injury, cerebrospinal fluid leakage, thoracic or abdominal organ injury, and segment instability. Surgeons must undergo extensive professional training and accumulate in-depth surgical experience to reduce the incidence of inaccurate screw placement. Screw fixation usually requires percutaneous access to the bone, followed by insertion of catheters, guidewires, and screw cannulas. Thanks to developments in X-ray and computed tomography (CT) technology, surgeons can delicately plan the path of percutaneous access using personalized preoperative images and three-dimensional (3D) reconstruction images, avoid important tissue features, such as nerves and blood vessels, and select the most appropriate percutaneous entrance and access angle. However, it is difficult to translate well-designed percutaneous access on the image to the actual patient. Additionally, in the absence of a guidance device, percutaneous access established by manual operation will inevitably deviate from the planned path. The limitations of human hands (manipulation) and eyes (positioning) have become increasingly apparent. The limitations of orthopedic surgery are that surgeons cannot see deep structures and cannot directly transfer the preoperative plan to the operation. Additionally, surgeons' hand stability may be insufficient in some sophisticated procedures. Because the clinical use of orthopedic surgical robots requires precise and stable positioning, soft tissue surgical robots, such as the Da Vinci system (Intuitive Surgical, Inc., Sunnyvale, CA, USA), are unsuitable for use as orthopedic surgical robots. To improve the accuracy of orthopedic surgery, clinicians and researchers have jointly developed a variety of robotic systems. [1] Many robotic systems for orthopedic surgery, such as Renaissance, ROSA Spine, and MAKO, have been used clinically. Robot-assisted orthopedic surgery can improve the accuracy of implant placement and promote computer-assisted minimally invasive surgery; [1] however, these systems also have inherent limitations. Research on orthopedic surgical robots has focused on using robots for a single indication, but not for multiple indications. Additionally, most robots are registered by preoperative CT or intraoperative two-dimensional (2D) fluoroscopy images, but not by intraoperative 3D reconstruction images. During surgery, it is difficult to translate the percutaneous access designed on the image to the patient without intraoperative 3D reconstruction images. Therefore, our work was focused on developing a solution for robot-assisted orthopedic surgery and creating an orthopedic surgical robot system for multiple indications. Here, we describe how our key technologies are applied to our orthopedic surgical robot. Our goal was to build a robotic solution to provide real-time positioning and posture guidance to help surgeons establish percutaneous screw trajectories. The robot determines the planned percutaneous trajectory, places the guide device on the corresponding position on the patient, and holds the device steady. Key operations, such as puncturing, drilling, and screw placement, are manually completed by the surgeon under the guidance of the device. Similar studies have evaluated surgical positioning systems; however, the clinical practicability and versatility of the system are important factors to consider. To achieve these goals, we developed an optical navigation surgical robot system. The operation planning software is specifically designed to adapt to X-ray, cone-beam CT, and other imaging modalities. A custom-designed robot navigation ruler and registration method are used to unify the medical image space and the robot workspace. The motion control strategy of the robot arm is divided into two stages, human–robot cooperation and robot autonomous motion, in which the robot arm can interact safely in the operation room and accurately locate the planned percutaneous access. The robot's end effector, i.e., the guide device, is specifically designed to adapt to different surgical instruments, such as a puncture needle or a bone drill. The surgical robot system consists of an assist-positioning robot arm, an optical navigation unit, and a surgery planning workstation, which are placed on three trolleys with brake casters [Figure 1].Figure 1: The surgical robot system and navigation scheme.To adapt to orthopedic surgery for all parts of the body and different percutaneous access angles, the robot arm has a large working space and flexible working postures. A serial configuration robot arm is used in our system, which has a full length of 850 mm and six degrees of freedom (DOF), with each DOF rotatable to ± 360°. With our specially designed end effectors for various surgical instruments, the robot can be used in orthopedic surgeries for the entire spine, from the cervical spine to the sacrum, as well as in a variety of trauma and joint surgeries. The motion control of the robot arm is achieved by sending the desired pose from the controller, and the clinical positioning accuracy is less than 1 mm. The optical navigation unit is composed of an optical tracker (NDI Polaris Spectra, Waterloo, ON, Canada) and two passive marker brackets. Four infrared reflective balls on each bracket are used to detect and obtain the position and attitude of the rigid body connected to the bracket. One bracket is fixed near the surgical site of the patient, and another is fixed on the flange of the robot's end effector. The typical space layout of the surgical robot system is shown in previous reports. [2] The surgery planning workstation contains a computer equipped with surgery planning software. The patient's intra-operative real-time medical images are transmitted to the computer. Combined with the percutaneous access planned by the surgeons, the expected posture of the robot arm is automatically calculated and sent for execution. In clinical surgery, the calibrator held by the robotic arm is placed just over the skin, as close as possible to the operating area. A set of intraoperative 3D radiographic images is acquired by the C-arm scanner and then transferred to the workstation. Screw trajectory planning is performed by the surgeon, and then the robotic arm moves toward the planned direction of the screw. Guidewires are inserted through the cannula on the robotic arm, which allows for real-time monitoring and adjustment; screws are inserted along the guidewires, and the screw positions are confirmed according to 3D images. The developed system is now being manufactured for commercial use. Hundreds of these orthopedic surgical robots have been deployed across China, and more than 30,000 orthopedic operations have been performed. The orthopedic surgical robot system makes full use of visual image guidance, and it combines the accuracy and stability of robotic surgery with the experienced decision-making ability of surgeons, which greatly improves the accuracy, safety, standardization, operation efficiency, and treatment effect of minimally invasive orthopedic surgery. Numerous clinical studies have confirmed the accuracy and safety of this robot system. Han et al[3] found that 95.3% of 532 thoracolumbar screws were placed perfectly in robot-assisted spinal surgery. Fan et al[4] found that 94.9% of 390 screws were placed acceptably in the cervical vertebrae. In a study by Wang et al, [5] the accuracy of robot-assisted percutaneous sacroiliac screw placement was found to be superior to that of the freehand technique. He et al[6] reported that robot-assisted placement of femoral neck cannulated screws can significantly reduce the duration of intraoperative fluoroscopy, drilling attempts, and operation. Guo et al[7] showed that robot-assisted scaphoid screw fixation improved implantation accuracy and shortened radiation exposure in a randomized controlled trial. In summary, we proposed a robotic solution for multiple orthopedic surgeries and developed a surgical robot system. The robot we studied can be applied to all segments of the spine (cervical spine to the sacrum) and can significantly improve the positioning accuracy of minimally invasive spinal surgery, while also avoiding the physiological shaking of the human hand, with highly repeatable results. Owing to its advantages of precise positioning, stability, and repeatability, robot-assisted spinal surgery can improve the results of clinical surgery. Funding This study was supported by grants from the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (CIFMS) (No. 2021-I2M-5-007), Beijing Natural Science Foundation (No. L212062), Beijing Hospitals Authority Innovation Studio of Young Staff Funding Support (No. 202109), and Beijing Jishuitan Hospital Youth Talent Training Project (No. XKXX202104). Conflicts of interest None.