Asymmetric Neck Bone Anchoring Member for Polyaxial Pivot
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Solution Overview
Problem
Existing polyaxial bone anchoring devices have limited pivot angles and lack sufficient strength under loads, which restricts their application in providing stable fixation in various anatomical orientations.
Innovation Solution
A polyaxial bone anchoring device with an asymmetric neck portion, featuring a recess on one side and an extension on the other, allowing for a larger pivot angle of up to 55°, while maintaining structural strength by not reducing the overall thickness of the neck portion, and an engagement portion for instruments to indicate the orientation of the enlarged pivot angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the neck portion is made asymmetric with a recess on one side to increase pivot angle, then the pivot angle is enlarged, but the structural strength may be compromised
Solution Approach 1:
The neck portion is designed with an asymmetric cross-section featuring a recess on one side and an extension on the opposite side. This asymmetry enables the anchoring member to pivot at different angles in different directions (e.g., 55° in one direction and 30° in the other), providing enhanced adaptability for various anatomical orientations while maintaining structural integrity through the extension that compensates for material removal.
Solution Approach 2:
The asymmetric neck portion applies local quality by concentrating the recess on one side and the extension on the other, allowing the structure to have different properties in different directions. The extension area provides additional material strength where needed, while the recess area allows for greater pivot clearance, resolving the contradiction between adaptability and strength.
2Adaptability or versatility
If the overall thickness of the neck portion is reduced to accommodate the asymmetric design, then the pivot flexibility is improved, but the strength and safety under loads is diminished
Solution Approach 1:
The asymmetric design with recess on one side and extension on the other allows the neck portion to achieve enhanced pivot flexibility without reducing the overall thickness. The extension compensates for the material removed in the recess, maintaining the overall thickness and structural strength while providing the necessary flexibility for polyaxial positioning.
3Adaptability or versatility
If an asymmetric neck portion with recess and extension is implemented, then the manufacturing complexity increases, but the device functionality is significantly improved
Solution Approach 1:
The asymmetric neck portion can be manufactured as a separate component or integrated into the anchoring member through modular design approaches. The recess and extension features can be created through standard manufacturing processes such as CNC machining or injection molding, making the increased complexity manageable while achieving significant functional improvements in pivot capability.
Data Source
AI summary
An anchoring member is provided suitable for use in a polyaxial bone anchoring device, the anchoring member (1) comprisinga bone anchoring section (2) with a bone engagement structure in at least a portion of an outer surface thereof;a head (3);a central axis (C) extending through a center of the head (3) and the bone anchoring section (2), anda neck portion (24; 24′; 24″; 24′″) between the bone anchoring section and the head, wherein the neck portion is asymmetric with respect to the central axis (C); andwherein the bone anchoring section (2) has a contour in a circumferential direction adjacent to the neck portion and wherein the neck portion is at least partially recessed with respect to the contour of the bone anchoring section at one side and extends beyond the contour of the bone anchoring section at an opposite side from the central axis.