Virtual Knee Joint Range of Motion Calculation
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Solution Overview
Problem
Current methods for determining the range of motion of an artificial knee joint before total knee arthroplasty are inadequate, as they often require invasive procedures and do not accurately predict post-operative functionality.
Innovation Solution
A data processing method that calculates the maximum varus and valgus angles of an artificial knee joint by acquiring the maximum lengths of the medial and lateral ligaments, using virtual positions and transformation matrices to simulate the range of motion without invasive manipulation, employing computer-aided simulations and non-surgical data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive procedures are used to determine range of motion, then measurement accuracy may be improved, but patient harm and procedural complexity increase
Solution Approach 1:
The patent creates a virtual copy of the knee joint anatomy including bones, ligaments, and implants through image processing. This digital model allows range of motion measurement without physically manipulating the patient's joint, thereby eliminating invasive procedures while maintaining measurement capability through computational simulation of ligament behavior and joint kinematics
Solution Approach 2:
The patent replaces physical mechanical measurement methods (which require manual manipulation and stress application to the joint) with computational mechanics. Transformation matrices and virtual simulations calculate ligament lengths and joint positions, substituting direct mechanical measurement with mathematical modeling to determine range of motion accurately without patient intervention or physical stress
2Measurement precision
If invasive procedures are used to determine range of motion, then measurement accuracy may be improved, but device complexity and procedural time increase
Solution Approach 1:
The patent integrates multiple functions into a single computational system: image processing to create 3D models, transformation matrix calculations for coordinate system alignment, virtual ligament length measurements, and range of motion computation all occur within one integrated software platform. This multi-functional approach consolidates what would otherwise require multiple separate devices and procedures into a unified system
Solution Approach 2:
The patent performs preliminary actions by pre-calculating transformation matrices from planning CT images and pre-establishing the virtual anatomical model before the actual range of motion measurement is needed. This preliminary setup allows rapid subsequent measurements without repeating complex calibration or model creation steps during the measurement process itself
3Object-affected harmful factors
If virtual simulation methods are used, then patient harm is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent incorporates feedback mechanisms where the virtual model is continuously refined based on transformation matrix calculations that compare planned implant positions with actual anatomical relationships. The system uses iterative optimization to adjust virtual ligament lengths and joint positions, ensuring the simulation accurately reflects the physical system it is modeling, thereby maintaining measurement precision
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting transformation matrices that define the spatial relationships between different anatomical coordinate systems. By varying these mathematical parameters based on individual patient anatomy and implant positioning, the system adapts the virtual model to accurately represent the specific case being analyzed, maintaining precision across different anatomical variations
Data Source
AI summary
A data processing method for determining a range of motion of an artificial knee joint which connects a femur and a tibia via a medial ligament and a lateral ligament, wherein at least the femur comprises an implant which forms a medial condyle and a lateral condyle, the method comprising the steps of: acquiring the maximum lengths of the lateral ligament and the medial ligament for a particular flexion angle of the knee joint; calculating a first virtual position between the femur and the tibia in which the lateral condyle of the femoral implant touches the tibia and the medial ligament is stretched to its maximum length; calculating a maximum valgus angle of the range of motion from the first virtual position; calculating a second virtual position between the femur and the tibia in which the medial condyle of the femoral implant touches the tibia and the lateral ligament is stretched to its maximum length; and calculating a maximum varus angle of the range of motion from the second virtual position.