Bone Anchor Coupling Structure for Polyaxial and Monoplanar Locking
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Solution Overview
Problem
Existing coupling devices for bone anchors in orthopedic surgery lack a simple structure that can facilitate both polyaxial and monoplanar functionalities, limiting flexibility and versatility in surgical applications.
Innovation Solution
A coupling device with a receiving part and a locking member that allows interchangeable use with different bone anchors, enabling either polyaxial or monoplanar configurations by adjusting the locking member's position, and featuring slits and cutout portions for enhanced pivot angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a coupling device is designed with a simple structure, then ease of manufacture and inventory management improve, but the ability to provide both polyaxial and monoplanar functionalities deteriorates
Solution Approach 1:
The coupling device is designed with a universal receiving part that can accommodate both monoplanar bone anchors (with wings) and polyaxial bone anchors (without wings or with spherical heads). The receiving part includes a head receiving portion with an accommodation space that adapts to different anchor types, and a locking member that can lock both types. This universal design allows a single coupling device structure to provide multiple functionalities (both polyaxial and monoplanar configurations) without requiring separate specialized devices for each anchor type.
Solution Approach 2:
The coupling device incorporates a dynamic locking mechanism that can adapt its configuration based on the inserted bone anchor type. The locking member is designed to engage with different anchor geometries (wings vs. spherical heads) through the same receiving part, allowing the device to dynamically adjust its locking approach. The head receiving portion can accommodate various anchor orientations and geometries, providing adaptive functionality within a single static structure.
2Adaptability or versatility
If different coupling devices are designed for polyaxial and monoplanar functionalities, then adaptability improves, but device complexity and inventory requirements worsen
Solution Approach 1:
The coupling device employs a universal receiving part design that eliminates the need for separate polyaxial and monoplanar coupling devices. The head receiving portion includes an accommodation space that can receive both monoplanar bone anchors (with wings) and polyaxial bone anchors (with spherical heads or without heads). The locking member is designed to engage with both anchor types through the same interface, allowing a single coupling device to replace what would traditionally require two different devices. This reduces inventory requirements and the quantity of different parts needed while maintaining adaptability to different anchor types.
3Ease of operation
If the head receiving portion has a locally reduced wall thickness for easy insertion, then ease of operation improves, but structural strength deteriorates
Solution Approach 1:
The head receiving portion of the coupling device is designed with non-uniform wall thickness, featuring locally reduced wall thickness in specific regions to facilitate easy insertion and expansion of the bone anchor head. These thinned regions are strategically positioned to allow the head to be inserted and expanded without excessive force. Conversely, other regions of the head receiving portion maintain thicker walls to provide sufficient structural strength and stability when the locking member clamps the inserted head. This local quality variation optimizes both ease of operation (insertion) and structural strength (clamping) in different locations of the same component.
Data Source
AI summary
A system for coupling a rod to bone includes different first and second bone anchors and a coupling device including a receiving part with a rod receiving portion for receiving a rod and a head receiving portion for interchangeably accommodating a head of either the first or second bone anchors, and a locking member positionable at least partially around the head receiving portion and movable between a first position where the held head is movable relative to the receiving part and a second position where the held head is locked relative to the receiving part. The coupling device includes a restraining surface configured to restrict pivoting of the first bone anchor relative to the receiving part, while the coupling device is configured to restrict pivoting of the second bone anchor relative to the receiving part differently than the restricted pivoting of the first bone anchor relative to the receiving part.