Femur Axis Reconstruction via 2D X-Ray Back-Projection
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Solution Overview
Problem
Current methods for determining the position and geometry of the femur shaft and neck axes during hip surgery rely on visual assessment or two-dimensional x-ray images, which are inadequate for precise three-dimensional positioning of artificial hip joints, especially in minimally invasive procedures, and expose patients to higher radiation with CT scans.
Innovation Solution
A method using multiple two-dimensional x-ray recordings from different directions, combined with generic models and image processing algorithms, to automatically determine the spatial position of characteristic axes like the femur neck and shaft axes, allowing for accurate alignment of implants without the need for CT scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CT recordings are used to determine three-dimensional position of femur axes, then measurement precision is improved, but radiation exposure to patient increases significantly
Solution Approach 1:
The patent uses two-dimensional x-ray images as copies or projections of the three-dimensional bone structure. By analyzing multiple 2D projections from different angles and reconstructing the 3D axes mathematically, the system achieves accurate position determination without requiring direct 3D CT imaging, thereby avoiding high radiation exposure while maintaining measurement precision
Solution Approach 2:
The patent transforms the problem from direct 3D imaging to 2D projection analysis. By capturing 2D x-ray images from multiple directions and using back-projection algorithms, the system reconstructs 3D spatial information from 2D data, achieving the same measurement goal with lower radiation dose
2Device complexity
If visual assessment is used to determine implant position, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces an image processing algorithm as an intermediary between the 2D x-ray images and the final implant positioning decision. The algorithm automatically detects bone contours, determines axis positions, and provides precise measurements to the surgeon, bridging the gap between simple imaging and accurate measurement without requiring complex surgical equipment
Solution Approach 2:
The patent replaces the purely visual/mechanical assessment method with an automated image processing system. Instead of relying on surgeon visual inspection alone, the system uses computer algorithms to analyze x-ray images, calculate axis positions, and guide implant placement, significantly improving measurement precision while keeping the surgical procedure relatively simple
3Measurement precision
If multiple two-dimensional recordings from different directions are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the complex 3D measurement task into separate 2D projection analyses. Each 2D image is processed independently to extract contour information and calculate axis positions in that specific view. The results from multiple 2D analyses are then combined through back-projection to determine the final 3D axis positions, breaking down the complex problem into manageable segments
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 method enables precise determination of characteristic axes, reducing complications and radiation exposure by allowing for optimal positioning of femur implants relative to the femur shaft and neck axes, thereby improving the fitting and longevity of artificial hip joints.
Implementation Method 1
at least one and preferably two or more two-dimensional recordings produced from different directions of a first area of the body structure and optionally also a second, different area of the body structure. The recordings, for example, can be two-dimensional x-ray recordings of the areas of the body structure
Data Source
AI summary
A method for determining a characteristic axis of a body structure includes generating at least two two-dimensional recordings of an area of the body structure; comparing each of the at least two recordings of the area with a generic model of the area in question, said generic model containing information on the position of the characteristic axis; ascertaining a mapping protocol for mapping the respective generic model onto the respective recording of the area; using the ascertained mapping protocol to map the respective position of the characteristic axis in the respective generic model to obtain the respective position of the characteristic axis in the two-dimensional mapping of the body structure; and using rear projection to determine a three-dimensional position of the characteristic axis from the at least two characteristic axes in the two-dimensional mappings.