Robotic Pedicle Drilling Control to Mitigate Tool Skiving
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Solution Overview
Problem
Robotic surgical systems face challenges in achieving accurate pedicle screw placement due to skiving at the entry point, inaccuracies in registration/mapping, and vertebral body movement during surgery, leading to potential nerve injuries from pedicle wall breaches.
Innovation Solution
A surgical system with a robotic manipulator and sensors that control a cutting bur to align with a target axis, sense forces, and adjust rotational speed and feed rate to penetrate cortical and cancellous bone regions, using virtual boundaries to prevent breaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a robotic manipulator is used to place pedicle screws, then positioning accuracy is improved, but skiving at the entry point causes deviation from the target trajectory
Solution Approach 1:
The system performs preliminary registration of anatomical landmarks and creates a virtual 3D model of the spine before the actual screw placement. This pre-planning phase allows the system to establish an accurate coordinate system and trajectory plan, compensating for potential skiving effects during the subsequent drilling operation by having the correct target path predetermined.
Solution Approach 2:
The robotic system incorporates real-time feedback through sensors that monitor the position and orientation of the drilling tool. The system continuously compares the actual tool trajectory with the planned virtual trajectory and makes dynamic adjustments to compensate for skiving effects, ensuring the drill bit remains aligned with the target pedicle entry point throughout the operation.
2Ease of operation
If registration/mapping of the spine CT scanned model with the robot's coordinate system is performed, then surgical planning is improved, but inaccuracies in this mapping lead to errors in tool placement
Solution Approach 1:
The system creates a virtual 3D copy of the patient's spine anatomy from CT scan data, which is then registered with the robotic coordinate system. This virtual model serves as a precise digital replica that can be manipulated and measured without physical constraints, allowing for accurate surgical planning and trajectory calculation while eliminating errors associated with physical model fabrication or manual measurement.
Solution Approach 2:
The system replaces manual mechanical registration methods with an automated computer-vision-based registration system. Optical markers and sensors automatically identify anatomical landmarks and establish the transformation between the CT coordinate system and the robotic coordinate system, eliminating human error and improving mapping accuracy compared to manual methods.
3Productivity
If the cutting bur rotates at high speed to penetrate cortical bone, then drilling efficiency is improved, but excessive force causes vertebral body movement and trajectory deviation
Solution Approach 1:
The system uses periodic or intermittent drilling action, alternating between high-speed cutting phases and low-speed advancement phases. During high-speed rotation, the bur removes bone efficiently, then the system pauses rotation and slowly advances the tool, allowing the vertebral body to settle and preventing cumulative movement that would occur with continuous high-speed drilling.
Solution Approach 2:
The robotic system dynamically adjusts the rotational speed and feed rate of the cutting bur based on real-time feedback from force sensors. When resistance increases indicating potential vertebral movement, the system automatically reduces speed or pauses, creating a dynamic control strategy that maintains both drilling efficiency and vertebral stability throughout the procedure.
Data Source
AI summary
Surgical systems and methods involve manipulation of a bone. A robotic manipulator supports and moves a surgical tool. Controller(s) define a virtual boundary to guide movement of the surgical tool to an entry point on a surface of the bone structure. The controller(s) define an operational limit on the surgical tool that limits a cutting speed and/or a feed rate of the surgical tool. The controller(s) control the robotic manipulator to facilitate movement of the surgical tool along a length of the virtual boundary and towards the entry point. The controller(s) detect that the surgical tool is located along the length of the virtual boundary, and in response, activate the operational limit for the surgical tool, e.g., to mitigate skiving of the surgical tool at the entry point.