Sequential Locking Assembly for Polyaxial Bone Anchoring Devices
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Solution Overview
Problem
Existing polyaxial bone anchoring devices require separate tools for locking the head and rod, making them more complex and less efficient in use, and often result in a larger, less compact design.
Innovation Solution
A locking assembly that allows sequential locking of the head and rod using a single tool with a single drive portion, where the outer locking element fixes the rod and the inner locking element fixes the head, enabling a more compact and low-profile design by transferring higher forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate tools are used for locking the head and rod, then the locking function is complete, but the device complexity increases and ease of operation decreases
Solution Approach 1:
The patent combines two separate locking operations (head locking and rod locking) into a single integrated locking assembly that can be operated with one tool. The first locking element engages the head while the second locking element engages the rod, allowing both to be locked simultaneously using a single drive portion, thereby reducing tool requirements and simplifying the operation process.
Solution Approach 2:
The locking assembly is designed with multi-functionality to perform both head locking and rod locking functions through a single assembly structure. The first locking element with engagement structure for a drive tool and the second locking element driven by the first locking element enable the system to complete multiple locking tasks that would traditionally require separate specialized tools.
2Volume of moving object
If separate locking elements are used for head and rod, then the locking function is complete, but the device becomes less compact
Solution Approach 1:
The patent implements a nested structure where the second locking element is arranged within or attached to the first locking element. This nested arrangement allows the locking components to be compactly organized, reducing the overall volume of the locking assembly while maintaining the necessary locking functions for both the head and rod.
3Ease of operation
If sequential locking is implemented, then the ease of operation improves, but the locking time increases
Solution Approach 1:
The locking assembly is pre-configured with the first locking element positioned to engage the head and the second locking element positioned to engage the rod. This preliminary arrangement of locking elements in the correct positions and orientations allows for rapid sequential locking operations without requiring additional positioning or adjustment steps during the locking process.
Data Source
AI summary
A locking assembly for securing a rod in a polyaxial bone anchoring device includes a first locking element having a first end, a second end, an outer surface with an external advancement structure, an inner wall, an internal advancement structure on the inner wall, and an engagement portion for a tool, and a second locking element having a first end configured to be oriented towards the first end of the first locking element, an opposite second end, an outer surface with an external advancement structure configured to cooperate with the internal advancement structure of the first locking element, and a portion at the second end having a width greater than a greatest width of the external advancement structure of the second locking element, wherein the second locking element is configured to move axially relative to the bone anchoring device at a speed different than the first locking element.