Inertial Sensor Surgical Navigation for Knee Alignment
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Solution Overview
Problem
Conventional knee replacement surgery instrumentation, such as the intramedullary rod and extramedullary guide, is invasive, prone to human error, and lacks accuracy, particularly in aligning surgical cuts beyond the coronal plane, leading to potential complications and reduced implant longevity.
Innovation Solution
A surgical navigation system utilizing two six-degree-of-freedom inertial sensors with integration, quaternion, and Kalman filter algorithms to track bones and surgical instruments, providing real-time visualization and guiding optimal cutting planes and implant positions without external references, thus eliminating line-of-sight issues and reducing invasiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mechanical instrumentation (intramedullary rod, extramedullary guide) is used for aligning surgical cuts, then the procedure can be performed with simple tools, but the alignment accuracy is insufficient and the procedure is highly invasive
Solution Approach 1:
The patent replaces conventional mechanical alignment instruments (intramedullary rods, extramedullary guides) with an optical navigation system that uses cameras, optical trackers, and computer processing to determine bone geometry and guide surgical cuts. This substitution eliminates the need for invasive mechanical jigs while achieving superior alignment accuracy through digital measurement and visualization.
Solution Approach 2:
The patent introduces an optical tracker as an intermediary device that attaches to the bone and serves as a reference point for the navigation system. The optical tracker enables the camera system to measure bone geometry without direct mechanical contact, reducing invasiveness while maintaining measurement precision through non-contact optical field interaction.
2Measurement precision
If intramedullary rod is used to align femoral cut guides, then the mechanical axis can be referenced, but the rod is highly invasive, causes blood loss, and may fracture inside the femur
Solution Approach 1:
The patent eliminates the intramedullary rod by using an optical navigation system to reference the mechanical axis. The system uses optical trackers on the bone surface and camera-based measurement to determine bone geometry, replacing the invasive mechanical rod with a non-invasive optical field-based approach that avoids blood loss and fracture risks.
Solution Approach 2:
The patent creates a digital copy or virtual model of the bone geometry through optical measurement and computer processing. This virtual representation allows the system to analyze and guide surgical cuts without requiring physical intramedullary rods inside the bone, thereby eliminating the harmful effects of rod placement while maintaining alignment precision.
3Object-affected harmful factors
If extramedullary guide is used to align tibial cut guide, then the guide remains outside the bone, but the guide lacks adequate fixation and is difficult to control
Solution Approach 1:
The patent replaces the extramedullary mechanical guide with an optical navigation system that uses cameras and optical trackers to determine bone geometry. This substitution eliminates the need for large external mechanical jigs that require manual holding, providing reliable control through optical field measurement without increasing invasiveness.
Solution Approach 2:
The patent uses an optical tracker as an intermediary that attaches securely to the bone surface, providing a stable reference point for the navigation system. This small, secure attachment replaces the large, manually-held extramedullary guide, providing reliable fixation through biological fixation rather than mechanical support.
4Device complexity
If mechanical jigs are used for alignment, then the procedure can be performed with simple tools, but the jigs only allow alignment in the coronal plane and lack sagittal verification
Solution Approach 1:
The patent replaces simple mechanical jigs with a complex optical navigation system that uses cameras, optical trackers, and computer processing to measure bone geometry in three dimensions. This substitution enables precise alignment verification in both coronal and sagittal planes through digital measurement and visualization, overcoming the limitations of mechanical jigs that can only align in the coronal plane.
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
The system achieves precise and repeatable alignment of cut guides and implants in three dimensions, reducing surgical complexity, minimizing blood loss, and freeing up operating space, while being less costly than optical navigation systems.
Implementation Method 1
two six-degree-of-freedom inertial sensors with integration, quaternion, and Kalman filter algorithms to track bones and surgical instruments
Data Source
AI summary
An inertial sensor based surgical navigation system for knee replacement surgery is disclosed. Inertial sensors composed of six-degree-of-freedom inertial chips, whose measurements are processed through a series of integration, quaternion, and kalman filter algorithms, are used to track the position and orientation of bones and surgical instruments. The system registers anatomically significant geometry, calculates joint centers and the mechanical axis of the knee, develops a visualization of the lower extremity that moves in real time, assists in the intra-operative planning of surgical cuts, determines the optimal cutting planes for cut guides and the optimal prosthesis position and orientation, and finally navigates the cut guides and the prosthesis to their optimal positions and orientations using a graphical user interface.