Bone Screw Length Measurement via 3D Model Reconstruction
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Solution Overview
Problem
During computer-assisted surgery, it is challenging for physicians to accurately determine the length of a bone screw to be inserted through a bore in a bone, especially when access is limited to one side, which can lead to instability or irritation from screw protrusion, and existing methods expose patients to excessive radiation.
Innovation Solution
A method using X-ray images to identify a predetermined drilling direction and position, transferring this information to a 3D bone model to calculate screw length, and utilizing a database of bone models to determine dimensions not visible in the projection image, reducing radiation exposure and improving implantation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple X-ray images are taken to accurately determine screw length, then measurement precision is improved, but radiation exposure to the patient increases
Solution Approach 1:
The patent transitions from 2D X-ray projection images to a 3D bone model to determine screw length. By reconstructing the bone geometry in three dimensions, the system can calculate the actual depth and orientation of the bore, enabling accurate screw length determination without requiring multiple radiation-exposing X-ray images from different angles.
Solution Approach 2:
The patent creates a virtual 3D copy of the bone based on a single X-ray projection image. This digital model replicates the bone's internal structure and geometry, allowing physicians to perform virtual measurements and determine screw length without exposing the patient to additional radiation from multiple physical X-ray images.
2Stability of the object's composition
If the screw is made longer to ensure sufficient bone engagement, then stability is improved, but soft tissue irritation increases due to protrusion
Solution Approach 1:
The patent replaces physical trial-and-error screw insertion with computer-based calculations. By using the 3D bone model to precisely calculate the required screw length based on bore depth and orientation, the system determines the optimal length that ensures sufficient bone engagement while preventing protrusion into soft tissue, eliminating the need for mechanical adjustment during surgery.
3Device complexity
If the physician attempts to measure bore depth directly from a single X-ray projection image, then device complexity is reduced, but measurement precision deteriorates due to obscured depth information
Solution Approach 1:
The patent solves the depth measurement problem by transitioning from 2D projection to 3D modeling. The system reconstructs the bone's three-dimensional geometry from the X-ray image, enabling accurate calculation of bore depth and orientation that cannot be obtained from the projection image alone, while maintaining relative system simplicity.
Data Source
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AI summary
A method and device is provided for identifying a length of a bone screw to be inserted through a bore drilled in a predetermined drilling direction at a predetermined position through a bone. The predetermined drilling direction and the predetermined position is identified in an X-ray projection image of the bone, and the identified direction and position is transferred to a corresponding model of the imaged bone, wherein the bone model is a 3D model. The length of the bone screw is finally determined at the bone model based on the transferred direction and position.