Robotic Bone Cutting Alignment Without Invasive Pin Fixation
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Solution Overview
Problem
Existing robotic systems for total knee arthroplasty require invasive attachment to the patient's bone, leading to potential bone fracture and inaccuracies due to manual adjustment of cutting planes and the need for separate devices for tibial cuts.
Innovation Solution
A surgical system with a robotic device featuring an end effector, actuation unit with three to five motorized degrees of freedom, a passive articulated lockable holding arm, and a tracking unit that adjusts the cutting tool's position and orientation in real time to align with target planes without invasive attachment, using a control loop to compensate for deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If invasive attachment using large pins is used to secure the robotic system to the bone, then the system can be firmly fixed, but it risks causing bone fracture and inaccuracies in cutting
Solution Approach 1:
The patent removes the invasive pins from the system entirely. Instead of attaching the robotic arm to the bone using large pins that risk fracture, the system uses a non-invasive optical tracking approach where markers are placed on the bone surface and tracked by external cameras, eliminating the harmful fixation method while maintaining positioning accuracy.
Solution Approach 2:
The patent replaces the mechanical pin-based fixation system with an optical tracking and control system. The robotic arm positions the cutting tool based on real-time optical tracking data and automated control algorithms, substituting physical mechanical attachment with a field-based (optical) measurement and control approach.
2Device complexity
If manual adjustment of rotational axes is used to position the cutting tool, then the system can be operated without complex automation, but it leads to inaccuracies in cutting alignment
Solution Approach 1:
The patent implements real-time feedback through optical tracking of markers on the bone and cutting tool, combined with feedback from force sensors during sawing. The control system continuously monitors the cutting plane alignment and automatically adjusts the robotic arm position to maintain precision, eliminating manual adjustment errors.
Solution Approach 2:
The robotic system performs self-positioning and self-alignment through automated control algorithms that process optical tracking data and sensor feedback. The system automatically compensates for misalignments and adjusts its own position without requiring manual intervention, achieving high precision through self-correcting mechanisms.
3Device complexity
If the robotic system cannot compensate for misalignments during sawing, then the system structure can be simpler, but it results in inaccurate cuts due to bone movement or positioning errors
Solution Approach 1:
The patent employs real-time feedback from force sensors mounted on the cutting tool that detect misalignments and bone movement during sawing. This feedback is transmitted to the control system, which automatically adjusts the robotic arm position to compensate for deviations, maintaining cutting accuracy throughout the procedure.
Solution Approach 2:
The patent implements dynamic compensation where the robotic system continuously adapts its position and orientation during the cutting process. The control system processes real-time data from optical tracking and force sensors to dynamically adjust the cutting plane alignment, transforming a static positioning system into a dynamic, self-correcting system that maintains precision despite bone movement or initial positioning errors.
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
Enables precise and accurate cutting of anatomical structures without invasive bone attachment, allowing all cuts to be performed with the patient's leg in a single position, reducing the risk of bone fracture and improving surgical efficiency.
Implementation Method 1
a tracking unit configured to determine in real time the pose of the cutting plane with respect to the coordinate system of the anatomical structure
Data Source
AI summary
A surgical system for cutting an anatomical structure (F, T) of a patient according to at least one target plane defined in a coordinate system of the anatomical structure comprises: (i) a robotic device (100) comprising: —an end effector comprising a cutting tool or a cutting block, —an actuation unit (4) comprising from three to five motorized degrees of freedom, attached to the end effector, configured for adjusting a position and orientation of the cutting tool or cutting block relative to each target plane, (ii) a passive articulated lockable holding arm (5) supporting the actuation unit (4); (iii) a tracking unit (200) configured to determine in real time the pose of the cutting plane with respect to the coordinate system of the anatomical structure, the tracking unit comprising a tracker configured to be rigidly attached to the actuation unit and a tracker configured to be rigidly attached to the end effector; (iv) a control unit (300) configured to determine the pose of the cutting plane with respect to the target plane and to control the actuation unit so as to bring the cutting plane into alignment with the target plane.