Robotic Cutting Bur Bone Cannulation with Dynamic Force Feedback
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Solution Overview
Problem
Robotic surgical systems face challenges in achieving accurate bone penetration and cannulation due to inaccuracies in registration, vertebral body movement, and potential nerve injury from pedicle screw insertion, particularly during pedicle screw placement in the spine.
Innovation Solution
A surgical system with a robotic manipulator and controllers that control a cutting bur to define virtual boundaries for lateral movement, align the bur to a target axis, and adjust rotational speed and feed rate based on sensed forces to penetrate cortical and cannulate cancellous bone regions, using sensors to monitor forces and adjust the bur's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rigid virtual boundary is used to constrain lateral movement of the cutting bur during cortical penetration, then positioning precision is improved, but the system lacks adaptability to tissue variations and forces
Solution Approach 1:
The virtual boundary is transformed from a static constraint to a dynamic one that adapts based on real-time force sensor feedback. The controller continuously adjusts the virtual boundary parameters (position, orientation, compliance) according to the measured interaction forces between the cutting bur and bone tissue, enabling the system to maintain precision while adapting to tissue variations and surgical conditions
Solution Approach 2:
Force sensors mounted on the cutting bur or robotic manipulator provide real-time feedback on interaction forces with the bone tissue. The controller uses this feedback to dynamically adjust the virtual boundary constraints, allowing the system to respond to tissue hardness variations, drilling depth, and potential deviations while maintaining accurate positioning
2Productivity
If the cutting bur rotates at high speed to efficiently penetrate cortical bone, then productivity is improved, but tissue trauma and forces applied to the bone structure increase
Solution Approach 1:
The cutting bur operates with periodic modulation of rotational speed and feed rate based on real-time force feedback. The controller adjusts operational parameters in cycles, increasing speed for efficient cortical penetration when forces are low, and reducing speed when force thresholds approach limits to minimize tissue trauma and prevent bone structure displacement
Solution Approach 2:
The system dynamically changes operational parameters (rotational speed, feed rate, depth) based on measured interaction forces and detected bone regions. High rotational speeds are used for cortical bone penetration when appropriate, while speeds are reduced during cancellous bone navigation or when force thresholds indicate risk of tissue damage, optimizing both efficiency and safety
3Manufacturing precision
If the robotic manipulator maintains strict control over the cutting bur trajectory, then manufacturing precision is improved, but the system cannot accommodate vertebral body movement and registration inaccuracies
Solution Approach 1:
Force sensors provide continuous feedback on interaction forces between the cutting bur and bone tissue. The controller uses this feedback to detect deviations from the planned trajectory caused by vertebral movement or registration inaccuracies, and dynamically adjusts the virtual boundary and control parameters to maintain accurate cannulation despite these variations
Solution Approach 2:
The virtual boundary constraints are made dynamic rather than fixed, allowing real-time adjustment of position and orientation based on force feedback and detected bone regions. This enables the system to adapt to vertebral body movement during surgery while maintaining precision in the final cannulation trajectory
4Reliability
If force thresholds are set low to prevent bone structure displacement, then reliability is improved, but the cutting bur cannot effectively penetrate cortical bone
Solution Approach 1:
The system uses periodic modulation of force thresholds and operational parameters based on detected bone regions. Lower force thresholds are applied when navigating cancellous bone or near critical structures to prevent displacement, while higher thresholds are permitted during cortical bone penetration phases when the cutting bur is actively removing material, enabling both safety and effectiveness
Solution Approach 2:
Force thresholds are dynamically adjusted based on real-time feedback from force sensors and detection of bone density variations. The controller increases allowable forces during cortical penetration when cutting efficiency is needed, then reduces thresholds when approaching cancellous bone or when force patterns indicate risk of bone structure displacement, optimizing both penetration capability and safety
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances accuracy and safety by maintaining controlled force thresholds during bone penetration and cannulation, reducing the risk of breaching cortical regions and minimizing tissue trauma.
Implementation Method 1
a surgical tool comprising a cutting bur rotatable about a cutting axis... to rotate the cutting bur about the cutting axis and laterally constrain the cutting bur according to the first virtual boundary to penetrate the first cortical region of the bone structure
Data Source
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Figure 3A~3D
AI summary
Disclosed herein are techniques for preparation of a bone structure wherein a robotically controlled cutting bur is utilized for both milling the entry point at the outer cortical region and cannulation of the cancellous bone region for receipt of an implant. A robotic manipulator supports and moves the cutting bur and one or more controllers analyze measurements from sensors and, in response, control the robotic manipulator and/or the cutting bur for purposes such as landmark detection to determine entry point, avoiding tool skiving at entry point, and avoidance of cortical wall breach during cannulation. Also described are techniques for managing feed rate, rotational cutting speed, or mode of operation depending on operational conditions surrounding various stages of cannulation. A control interface is also provided to enable the user to manage or adjust cutting bur operation and feed rate.