Polyaxial Bone Anchoring Device Asymmetrical Pivot Angle
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Solution Overview
Problem
Existing polyaxial bone anchoring devices lack the flexibility to provide an enlarged pivot angle to one side, limiting their application in various spinal fixation procedures.
Innovation Solution
A bottom-loading polyaxial bone anchoring device with a receiving part that allows for modular assembly with different bone anchoring elements, featuring a design with intersecting passages that enable an asymmetrical pivot angle, reducing the need for additional parts and minimizing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyaxial bone anchoring device is designed with symmetrical pivot angles, then the device structure remains simple and manufacturing is easier, but the application versatility is limited
Solution Approach 1:
The patent applies asymmetry by designing the receiving part with an asymmetrical internal geometry that provides different pivot angles in different directions. Specifically, the receiving part has a first passage and a second passage with different diameters, and the seat for the head is positioned asymmetrically, allowing the bone anchoring element to pivot to a greater angle in one direction than the other. This asymmetric design enables the device to accommodate various spinal fixation procedures with different angular requirements without needing multiple separate devices.
2Adaptability or versatility
If a polyaxial bone anchoring device is designed with top-loading configuration, then the assembly process is simpler, but the modular flexibility and variety of applications are reduced
Solution Approach 1:
The patent inverts the conventional top-loading configuration by implementing a bottom-loading design. The bone anchoring element is inserted from the bottom end of the receiving part through the first passage, rather than from the top. This inversion allows for greater modular flexibility because the element can be pre-assembled with the receiving part in different configurations, and the bottom-loading approach facilitates easier removal and replacement of components, enhancing the variety of applications while maintaining reasonable assembly simplicity.
3Adaptability or versatility
If multiple different bone anchoring elements are manufactured and stocked, then the variety of applications is covered, but the stockholding costs increase
Solution Approach 1:
The patent applies universality by designing a single receiving part that can accommodate multiple different bone anchoring elements with varying shank diameters, thread forms, and other features. The receiving part's asymmetrical design with passages of different diameters allows it to universally accept various anchoring elements, enabling a surgeon to use one receiving part for multiple different applications rather than maintaining separate devices for each specific application, thereby reducing stockholding variety and costs.
Data Source
AI summary
A bone anchoring device includes a bone anchoring element with a spherical segment-shaped head, a receiving part configured to couple a rod to the bone anchoring element, and having a top end, a bottom end, a first passage at the bottom end with a first longitudinal axis, and a second passage at the top end with a second longitudinal axis that intersects the first longitudinal axis, a compression element, and a locking element. The receiving part also has a recess for the rod, the recess extending from the top end towards the bottom end and having a bottom that extends along an axis that is perpendicular to the second longitudinal axis. The receiving part or the compression element further has a seat. The compression element is configured to move along the first longitudinal axis while the locking element is configured to move along the second longitudinal axis.