Sparse Contact Tibia Jig Using MRI Slice Segmentation
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Solution Overview
Problem
Current knee replacement procedures using full segmentation for three-dimensional modeling are time-consuming, prone to geometrical errors, and limited in mass manufacturing, requiring dense grids of points that introduce mathematical inaccuracies and are not suitable for semi-custom instruments.
Innovation Solution
A sparse contact tibia cutting jig mechanism using a small number of MRI slices and contact points, reducing the number of required coordinates and design time, allowing for semi-custom design and fabrication of knee replacement components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If full segmentation with dense three-dimensional grid of points is used to accurately represent knee joint surfaces, then measurement precision and manufacturing precision are improved, but device complexity and time consumption increase significantly
Solution Approach 1:
The patent divides the complex three-dimensional surface representation into multiple two-dimensional MRI slices. Instead of using a dense 3D grid of points, the method segments the volume into sequential 2D cross-sections that can be processed and stored more efficiently, reducing overall system complexity while maintaining accuracy.
Solution Approach 2:
The patent creates simplified two-dimensional copies (MRI slices) of the three-dimensional anatomical structure. These 2D representations serve as accurate proxies for the full 3D geometry, eliminating the need for complex 3D grid calculations while preserving essential surface information for surgical planning.
2Manufacturing precision
If full segmentation with dense grid points is used, then manufacturing precision is improved, but productivity and ease of manufacture deteriorate due to 4-20 hours of numerical work required
Solution Approach 1:
The patent uses two-dimensional MRI slices as simplified copies of the three-dimensional anatomy. This approach reduces the computational burden from generating dense 3D grids to processing sequential 2D images, dramatically decreasing processing time from 4-20 hours to a much more efficient operation suitable for mass manufacturing.
Solution Approach 2:
The patent changes the dimensional parameter from three-dimensional to two-dimensional representation. By transforming the problem from 3D grid coordinate generation to 2D slice processing, the computational complexity and time requirements are significantly reduced while maintaining sufficient accuracy for surgical applications.
3Measurement precision
If dense grid points with close spacing are used, then measurement precision is improved, but geometrical errors and mathematical inaccuracies increase due to high-degree polynomials
Solution Approach 1:
The patent segments the continuous three-dimensional surface into discrete two-dimensional MRI slices. This segmentation avoids the need for high-degree polynomial fitting required in dense 3D grids, thereby eliminating the mathematical instabilities and geometrical errors that arise from such complex curve fitting while maintaining precise surface representation.
Data Source
AI summary
A tibia cutting jig mechanism (TCJM) is provided having a number N1 of spaced apart TCJM contact points that correspond to a number N1 of spaced apart knee contact points on at least one of a tibia plateau surface and a tibia shaft surface. The TCJM contact points are positioned in contact with the tibia contact points, and a cut bar guide is positioned in contact with the TCJM to provide a location and an angular orientation of a cut bar plane that is to be used to resection and remove a selected portion of the patient's tibia. The TCJM is removed from the patient's knee, and a selected portion of the patent's tibia is resectioned and removed. The number N1 is at most about seven in some embodiments.