Bone Anchor Coupling With Reversible Head Clamping Control
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Solution Overview
Problem
Existing polyaxial bone anchoring devices lack flexibility in allowing repeated and easy correction steps during surgery, limiting their effectiveness in adjusting the position of the bone anchor head.
Innovation Solution
A coupling device with a receiving part and a pressure member that allows for a flexible portion to clamp the bone anchor head, enabling easy clamping and unlocking through an instrument, and providing multiple locking options, including full locking and frictional clamping, with automatic centering and alignment of engagement structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure member is designed to provide strong locking force, then the bone anchor head is securely locked, but the device loses flexibility for repeated correction steps
Solution Approach 1:
The pressure member is designed to be movable between different positions (first position for strong locking, second position for frictional clamping) along the central axis. This dynamic positioning allows the system to switch between secure locking and flexible correction modes, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The locking force parameter can be changed by moving the pressure member between positions. In the first position, maximum locking force is applied; in the second position, reduced frictional clamping force is applied. This parameter change enables the system to adapt between secure locking and easy correction.
2Ease of operation
If the pressure member is moved to the second position for easy unlocking, then correction steps become easier, but the locking force is reduced
Solution Approach 1:
The pressure member can be dynamically repositioned along the central axis. When moved to the second position, it provides easy unlocking and correction; when moved to the first position, it provides strong locking. This dynamic capability allows easy operation when needed while maintaining strong locking when required.
Solution Approach 2:
The passage is segmented into different regions (first region for strong locking, second region for easy correction). The pressure member can be positioned in different segments to achieve different functional states, allowing easy unlocking in the second region while maintaining strong locking capability in the first region.
3Reliability
If the pressure member engages the inner wall for strong clamping, then the head is securely locked, but the flexible portion is highly compressed
Solution Approach 1:
The pressure member can be moved between positions to dynamically adjust the compression level of the flexible portion. In the first position, high compression provides secure clamping; in the second position, reduced compression eases the stress on the flexible portion while maintaining functional clamping.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates easy and repeated adjustment of the bone anchor head position, allowing for precise unlocking and locking, even when the rod is not in the channel, enhancing surgical flexibility and versatility.
Implementation Method 1
The pressure member has a flexible portion defining a hollow interior to accommodate and clamp the head therein
Data Source
AI summary
A coupling device for coupling a rod to a bone anchor includes a receiving part having a central axis, a coaxial passage, and an engagement recess extending laterally into the passage, and a pressure member having an expandable portion to clamp the head, a radially outwardly facing surface, and an engagement surface extending from the radially outwardly facing surface. The engagement surface of the pressure member is recessed from an outer surface of the receiving part. The pressure member is movable axially from a first position towards a second position where the receiving part directly engages the pressure member to increase a compression force on the expandable portion for clamping an inserted head. The engagement surface of the pressure member is engageable through the engagement recess of the receiving part by the instrument to move the pressure member axially from the second position back towards the first position.