Joint Laxity Measurement Using Bi-Planar X-Ray Imaging
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Solution Overview
Problem
Current methods for determining joint laxity are subjective, inaccurate, time-consuming, and expose patients to excessive radiation, limiting their applicability and reliability in clinical settings.
Innovation Solution
A method and system using patient-specific geometrical models and actual images obtained under applied loads to calculate relative bone displacement and rotation, allowing for a quantitative and reproducible measurement of joint laxity, with reduced radiation exposure using a bi-planar X-ray scanner like the EOS system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual assessment by doctor is used, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent replaces manual mechanical assessment by doctors with an automated optical imaging system (EOS bi-planar X-ray scanner) that captures bone positions and calculates laxity parameters automatically, eliminating subjectivity while maintaining ease of use
Solution Approach 2:
The system creates digital 3D models (copies) of the patient's bones from X-ray images, allowing precise measurement of bone positions and movements without requiring manual physical manipulation or interpretation
2Measurement precision
If MRI scan is used to estimate relative movement of bones, then measurement precision is improved, but loss of time deteriorates
Solution Approach 1:
The system uses rapid sequential X-ray imaging to capture bone positions at different loading stages, providing the necessary temporal resolution for laxity measurement without requiring the patient to remain still for extended periods as in MRI
Solution Approach 2:
The patent extracts only the essential information needed for laxity measurement (bone positions at different loads) using a rapid imaging method, eliminating the need for prolonged scanning required by MRI while maintaining measurement accuracy
3Measurement precision
If MRI scan is used, then measurement precision is improved, but object-affected harmful factors deteriorates
Solution Approach 1:
The system uses conventional X-ray imaging instead of expensive MRI, accepting lower cost imaging that can be performed repeatedly without the same level of resource consumption or patient discomfort, making it suitable for routine clinical assessment
Solution Approach 2:
The patent converts the traditionally harmful aspect of X-ray radiation into a benefit by using very low-dose bi-planar imaging that provides sufficient diagnostic information while minimizing radiation exposure, making repeated assessments safe
4Measurement precision
If X-ray is used to assess relative position and orientation of bones, then measurement precision is improved, but object-affected harmful factors deteriorates
Solution Approach 1:
The system uses bi-planar (two-dimensional) X-ray imaging to capture three-dimensional bone positions, extracting sufficient spatial information for laxity measurement without requiring higher-dose three-dimensional imaging
Solution Approach 2:
The patent applies only the minimum necessary radiation dose required to obtain accurate bone position measurements, avoiding excessive exposure while maintaining measurement precision through optimized imaging protocols
5Measurement precision
If bone-fixed measurement is used, then measurement precision is improved, but device complexity deteriorates
Solution Approach 1:
The patent replaces invasive mechanical bone fixation with non-invasive optical tracking of bone surfaces using X-ray imaging, achieving equivalent measurement precision without surgical implants or complex fixation devices
Solution Approach 2:
The system creates virtual 3D models of bones from external X-ray images, allowing precise measurement of bone positions and movements without physical attachment to the bones, simplifying the measurement system while maintaining accuracy
6Ease of operation
If skin surface measurement is used, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent introduces X-ray imaging as an intermediary that directly visualizes bone positions through soft tissue, eliminating the inaccurate skin surface measurements while maintaining ease of operation through automated image capture and analysis
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
Enables a well-defined, reproducible, and time-efficient assessment of joint laxity with lower radiation exposure, suitable for various joints and clinical applications, including post-operative assessments.
Implementation Method 1
A method and system using patient-specific geometrical models and actual images obtained under applied loads to calculate relative bone displacement and rotation, allowing for a quantitative and reproducible measurement of joint laxity, with reduced radiation exposure using a bi-planar X-ray scanner like the EOS system
Data Source
AI summary
The invention relates to a method of determining the laxity of a joint (9, 15) of a human (5) or an animal. The method comprises providing at least one patient-specific geometrical model (1) of at least one bone and/or at least one prosthesis comprised by the joint. Known loads are applied to the joint or to a part of the body connected to the joint, and a series of actual images (16) of the joint are obtained while the loads are applied. Then the at least one patient-specific geometrical model (1) is registered onto the actual images (16). Based thereon relative displacement and/or rotation of the at least one bone and/or at least one prosthesis is calculated as a function of the applied loads, and based thereon a measure of the laxity of the joint is determined. The invention further relates to a system for performing such a method and to a computer readable medium for performing such a method.