Asymmetric Rod Spinal Stabilization Device Anti-Slip Fixation
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Solution Overview
Problem
Existing spinal stabilization devices face challenges in maintaining secure fixation and preventing slipping of rods with circular cross-sections during rotational corrections, leading to limited rotational force application and stability issues.
Innovation Solution
A stabilization device featuring a rod with n-fold rotational symmetry and corresponding contact surfaces in the receiving part and fixation member, creating a form-fit connection that reduces slipping risk and allows for higher rotational forces, enabling more effective vertebral correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rod with circular cross-section is used, then the rod can be easily inserted and handled, but the receiving part slips around the rod axis during rotational corrections
Solution Approach 1:
The rod is designed with an asymmetric cross-section featuring a flat portion and a curved portion, eliminating the rotational symmetry of a circular cross-section. This asymmetric geometry creates a form-fit connection with the receiving part that prevents slipping during rotational corrections while maintaining ease of insertion and handling.
2Device complexity
If a rod with circular cross-section is clamped in the receiving part, then the device structure is simple, but rotational forces cause slipping around the rod axis
Solution Approach 1:
The asymmetric rod cross-section with flat and curved portions creates a form-fit connection that inherently prevents rotational slipping. This geometric solution achieves reliable fixation under rotational loads without requiring complex additional fixation mechanisms, thus maintaining relative structural simplicity while dramatically improving reliability.
3Reliability
If the rod has n-fold rotational symmetry with distinct external surfaces, then the risk of slipping is reduced and higher rotational forces can be applied, but the manufacturing complexity increases
Solution Approach 1:
The rod features an asymmetric cross-section with a flat portion and a curved portion, which can be manufactured using standard metal forming and machining processes. This design achieves improved anti-slipping performance and rotational force capacity through geometric configuration rather than material complexity, balancing manufacturing ease with enhanced mechanical performance.
Data Source
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AI summary
A stabilization device for bones or vertebrae is provided comprising: a rod (20, 20') having a rod portion with a rod axis (L) and with a number (n) of distinct external surfaces (21a, 21b, ...21i; 21a', 21 b', ...21i') that are arranged in an n-fold rotationally symmetrical manner around the rod axis (L), a bone anchoring device (1, 1', 100) including a receiving part (3, 105) comprising a channel for receiving the rod portion, wherein the receiving part includes a rod support (8, 8', 173); a fixation member (40, 40", 400) for fixing the rod in the channel; wherein the rod support (8, 8', 173) and the fixation member (4,4", 400) each comprise at least one contact surface (8a, 8b; 8a', 8b'; 173a, 173b) that is configured to contact an external surface of the rod portion, and wherein said contact surfaces (8a, 8b; 8a', 8b'; 173a, 173b) and said external surfaces (21a, 21 b, ...21i; 21a', 21b', ...21i') are configured and arranged to clamp the rod portion along at least three surface areas.