Existing methods to improve the accuracy of tibiofibular joint reduction present workflow challenges, high radiation exposure, and a lack of accuracy and precision, leading to poor surgical outcomes. To address these limitations, we propose a method to perform robot-assisted joint reduction using intraoperative imaging to align the dislocated fibula to a target pose relative to the tibia. The approach (1) localizes the robot via 3D-2D registration of a custom plate adapter attached to its end effector, (2) localizes the tibia and fibula using multi-body 3D-2D registration, and (3) drives the robot to reduce the dislocated fibula according to the target plan. The custom robot adapter was designed to interface directly with the fibular plate while presenting radiographic features to aid registration. Registration accuracy was evaluated on a cadaveric ankle specimen, and the feasibility of robotic guidance was assessed by manipulating a dislocated fibula in a cadaver ankle. Using standard AP and mortise radiographic views registration errors were measured to be less than 1 mm and 1° for the robot adapter and the ankle bones. Experiments in a cadaveric specimen revealed up to 4 mm deviations from the intended path, which was reduced to ⪅2 mm using corrective actions guided by intraoperative imaging and 3D-2D registration. Preclinical studies suggest that significant robot flex and tibial motion occur during fibula manipulation, motivating the use of the proposed method to dynamically correct the robot trajectory. Accurate robot registration was achieved via the use of fiducials embedded within the custom design. Future work will evaluate the approach on a custom radiolucent robot design currently under construction and verify the solution on additional cadaveric specimens.
Accurate, image-based planning of joint reduction based on intraoperative cone-beam CT forms the basis for precise robotic assistance and quantitative fluoroscopic guidance. The proposed approach combines statistical shape and pose modeling of the ankle joint to: (1) automatically segment individual bones; and (2) identify the target pose for the dislocated fibula to establish a plan for reduction. Leave-one-out analysis of the atlas members demonstrated accurate segmentation with 0.6 mm mean surface distance error and predicted the fibula pose within 1.6 mm and 1.8°. Future work will expand evaluation and analyze the appropriateness of the contralateral ankle as a patient-specific template.
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