Condyle Digitizer with Perpendicular Planar Surfaces for CAS
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Solution Overview
Problem
Current Computer Assisted Surgery (CAS) systems for Total Knee Replacement (TKR) surgery face challenges in accurately determining the most distal point on the femoral condyles, leading to potential measurement inaccuracies and improper resection cuts due to the use of digitizing pointers that can penetrate soft tissues and result in errors.
Innovation Solution
A CAS system and method utilizing a digitizer with perpendicular planar surfaces that are trackable in three-dimensional space, allowing for precise determination of the most remote reference point on the femoral condyles by creating a digitized plane and using a tracking system to determine the location of this point in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a digitizing pointer is used to determine the most distal point on the femoral condyles, then the measurement process is simple and quick, but the measurement precision deteriorates because the pointer tip can penetrate soft tissues and cartilage leading to inaccurate readings
Solution Approach 1:
The patent introduces a flat probe tip as an intermediary measurement tool that interacts with the bone surface through its entire flat face rather than a single point. This flat surface acts as a mediator that can be positioned against the condyle surface, allowing the system to identify the most distal point by detecting when the flat probe face is tangent to the condyle surface, thereby avoiding penetration issues while maintaining ease of use
Solution Approach 2:
The invention transitions from point-based measurement (0D) to surface-based measurement (2D) by using a flat probe tip with planar surfaces. The tracking system monitors the position and orientation of the flat probe in three-dimensional space, enabling the system to determine when the probe face is tangent to the condyle surface by analyzing the spatial relationship between the probe's planar surfaces and the bone geometry, thus improving accuracy without sacrificing operational simplicity
2Measurement precision
If a tracked guide block abutting the distal end of femoral condyles is used, then the location of the most distal point can be determined, but the device complexity increases due to the need for additional tracking and positioning mechanisms
Solution Approach 1:
The patent divides the measurement function into two independent components: a simple flat probe tip for physical contact with the bone, and a separate tracking system that monitors the probe's position and orientation. This segmentation allows the probe itself to remain mechanically simple while the tracking system handles the complex computational tasks of determining tangency and identifying the most distal point, thereby reducing overall device complexity while maintaining high measurement precision
Solution Approach 2:
The invention replaces complex mechanical positioning mechanisms (such as tracked guide blocks with multiple degrees of freedom) with a simpler approach: a flat probe tip whose position and orientation are monitored by an optical or electromagnetic tracking system. The complex calculations for determining the most distal point are performed computationally rather than through mechanical means, substituting mechanical complexity with computational processing
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 approach enhances the accuracy of determining the most distal point on the femoral condyles, reducing measurement errors and improving the precision of resection cuts, thereby ensuring a better fit of prosthetic implants.
Implementation Method 1
a digitizer having a trackable member which is locatable and trackable in three dimensional space by the computer assisted surgery system
Data Source
AI summary
A computer assisted surgery system for conducting orthopedic surgery on a knee joint includes a condyle digitizer having a posterior condyle abutment surface defining a first plane and a distal condyle abutment surface defining a second plane perpendicular to the first plane, and a trackable member which is locatable and trackable in three dimensional space by the computer assisted surgery system to define at least orientation of the condyle digitizer in real time. A computer determines a most remote reference point of the femur of the knee joint lying within at least one of the first and second planes when the condyle digitizer is abutted against condyles of the femur such that the posterior condyle abutment surface abuts a posterior side of the condyles and the distal condyle abutment surface abuts a distal side of the condyles.