Polyaxial Bone Anchor Preload Clamping Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyaxial bone anchoring devices face difficulties in aligning and inserting stabilization rods, especially in complex clinical applications where multiple bone anchors are connected, due to the free pivoting of the anchoring element's head before locking, which complicates the alignment and insertion process.
Innovation Solution
A polyaxial bone anchoring device that allows temporary clamping of the anchoring element's head in a desired angular position without locking, using a pressure element to exert a preload and prevent free pivoting, facilitating easier alignment and insertion of the stabilization rod, and enabling adjustments without complete unlocking, while allowing for stepless adjustability and reversible friction force using set screws.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the head of the anchoring element is allowed to pivot freely before locking, then the device maintains adjustability, but alignment and insertion of the rod becomes difficult
Solution Approach 1:
The pressure element is advanced to exert a preload on the head before final locking occurs, temporarily clamping the head in the desired angular position. This preliminary action stabilizes the assembly, making it easier to align and insert the rod without sacrificing the ability to adjust the angular position before locking
2Ease of operation
If the head is temporarily clamped with preload, then alignment and insertion becomes easier, but the head cannot be adjusted freely
Solution Approach 1:
The system transitions from a static locked state to a dynamic intermediate state where the pressure element applies controlled preload. This dynamic state allows the head to be temporarily clamped for alignment while still permitting adjustments by reversing the friction force through the pressure element, combining stability with adaptability
3Ease of operation
If a pressure element is used to exert preload on the head, then the head is prevented from free pivoting, but the device complexity increases
Solution Approach 1:
The pressure element serves multiple functions: it applies preload to temporarily clamp the head for alignment, maintains the anchoring element's angular position, and enables reversible friction-based locking. By integrating these functions into a single component that works with existing receiving parts, the patent avoids significant increases in device complexity while achieving improved ease of operation
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
Improves handling during surgery by simplifying the alignment and insertion of multiple bone anchors, allowing for precise preload adjustment and maintaining the desired angular position, while reducing manufacturing complexity and costs, and enabling safer pre-assembled devices with reduced risk of misalignment.
Implementation Method 1
the pressure element and the receiving part are configured to cooperate in such a way that the pressure element can frictionally clamp the head to maintain a desired angular position
Implementation Method 2
a friction force exerted by the set screws is reversible by loosening the set screws
Data Source
AI summary
A polyaxial bone anchoring device includes an anchoring element having a shaft and a head, a receiving part having a first end and a second end, a bore extending from the first end towards the second end, a seat for receiving the head, and at least one threaded through hole transverse to the bore, a pressure element to exert pressure onto the head, such that the head is pivotable and can be locked at an angle relative to the receiving part, the pressure element having at least one hole configured to at least partially align with the through hole, and at least one set screw threadable into the through hole to engage the pressure element at the hole such that a force is exerted by the pressure element onto the head that maintains the head at an adjustable angular position relative to the receiving part by friction.