MEMS Bone Tool Tracking via Coordinate Transformation
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Solution Overview
Problem
Current methods for calibrating tools in computer-assisted orthopedic surgery using microelectromechanical sensors (MEMS) often require complex manipulations and direct rigid connections, limiting the accuracy and flexibility of tracking bones and tools, especially when tools like cutting blocks need to be oriented relative to bones with multiple degrees of freedom.
Innovation Solution
A computer-assisted surgery system that includes a reference tracker with a MEMS unit secured to the bone, a tool with a MEMS unit initialized for tracking, and a processing unit that creates a frame of reference, allowing for the calibration and tracking of tools like cutting blocks with orientation adjustment mechanisms, enabling secure and accurate tracking without a direct rigid connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct rigid connection is used between tool and bone, then tracking accuracy is improved, but flexibility and ease of operation deteriorate
Solution Approach 1:
The patent introduces an intermediary calibration process that establishes a mathematical relationship between the tool's coordinate system and the bone's frame of reference without requiring a direct rigid mechanical connection. The tool calibrator acts as a mediator that records the transformation matrix between the tool MEMS unit and reference tracker, enabling accurate tracking while maintaining operational flexibility.
Solution Approach 2:
The patent replaces the mechanical rigid connection system with an optical/electronic tracking system using MEMS sensors and coordinate transformation mathematics. Instead of mechanically constraining the tool to the bone, the system uses electromagnetic field-based tracking and computational geometry to achieve accurate positioning and orientation.
2Measurement precision
If complex manipulations are required for calibration, then measurement precision is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The patent performs preliminary calibration actions by recording the transformation relationship between the tool and bone coordinate systems during an initialization phase. The tool calibrator captures the initial orientation and position data, storing it as a transformation matrix that is then used for all subsequent tracking operations, eliminating the need for complex real-time manipulations.
Solution Approach 2:
The system enables self-calibration through automated coordinate system registration. The processing unit automatically calculates the transformation matrix between the tool MEMS unit and reference tracker coordinate systems using the recorded data, reducing the need for manual intervention and complex operator manipulations during calibration.
3Reliability
If direct rigid connection is used for tool calibration, then tracking reliability is improved, but adaptability and versatility worsen
Solution Approach 1:
The patent transitions from a static rigid mechanical connection to a dynamic computational model. The transformation matrix between tool and bone coordinate systems can be updated and adjusted as needed, allowing the system to adapt to different surgical scenarios, tool orientations, and bone geometries while maintaining tracking reliability through continuous mathematical transformation.
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
This system enhances the accuracy and flexibility of tracking bones and tools by allowing secure calibration and orientation of tools relative to bones with multiple degrees of freedom, improving the precision of surgical operations and reducing the complexity of manipulations required.
Implementation Method 1
a reference tracker with a MEMS unit for outputting tracking data relating to an orientation of the reference tracker
Implementation Method 2
a tool with a MEMS unit preset with an initial orientation for outputting tracking data relating to an orientation of the tool
Data Source
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AI summary
A method tracks a tool with respect to a bone in computer-assisted surgery. A reference tracker with a MEMS unit is secured to the bone. The tracker outputs data relating to its orientation. A tool provided with a MEMS unit and secured to the bone is preset with an initial orientation. The tool outputs tracking data related to orientation of the tool once initialized. A trackable frame of reference relating the bone to the orientation of the tracker is created. The MEMS unit of the tool is initialized. A relation between the initial orientation of the tool and the orientation of the tracker at initialization of the MEMS unit of the tool is recorded. Orientational data of the tool relative to the frame of reference of the bone calculated using the relation is displayed. A computer-assisted surgery system for tracking a tool with respect to a bone after an initialization of a MEMS unit is also described.