Bone Anchor Head Preload Clamping for Releasable Angle Fixation
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Solution Overview
Problem
Existing bone anchoring devices face challenges in providing improved handling during surgery and are costly to manufacture, with a need for simplified design and efficient angular adjustment of the stabilization rod.
Innovation Solution
A bone anchoring device with a pivotably connected bone anchoring element and receiving part, utilizing a pressure element and a closed ring to achieve temporary clamping and adjustable angular positioning of the head, allowing for easy rod insertion and adjustment without complete loosening, and featuring a simple design with few parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional locking mechanism is used to fix the head angular position, then the head is securely locked, but the device complexity increases and surgical handling becomes more difficult
Solution Approach 1:
The invention extracts the locking function from a complex multi-component mechanism and implements it through a simple friction-based interface. The head includes a friction surface that directly contacts the rod, eliminating the need for separate locking nuts, clips, or cam mechanisms. This extraction of the locking function to a fundamental friction interface resolves the contradiction between reliable fixation and device complexity.
Solution Approach 2:
The head structure itself provides the locking capability through its friction surface, without requiring external locking components. The head serves dual functions: positioning the rod and securing it through friction. This self-service approach where the head performs both positioning and locking functions reduces device complexity while maintaining reliability.
2Stability of the object's composition
If the head is fully locked in position, then angular stability is achieved, but adjustments become impossible without complete loosening
Solution Approach 1:
The locking mechanism transitions from a static fully-locked or fully-loosened state to a dynamic continuum of friction-based holding forces. By controlling the friction coefficient and contact pressure between the head's friction surface and the rod, the system allows for adjustable stability - maintaining angular stability during use while permitting adjustments when needed, without requiring complete loosening.
Solution Approach 2:
The system utilizes parameter changes in friction force to control the locking state. By varying the normal force between the head and rod, or modifying the friction coefficient through material selection or surface treatment, the system can transition between adjustable and stable states. This parameter-based control enables both adaptability and stability without mechanical locking components.
3Manufacturing precision
If multiple components are used to achieve angular adjustment, then positioning precision is improved, but manufacturing costs increase
Solution Approach 1:
The invention merges the angular adjustment function and the locking function into a single integrated head structure. Instead of separate adjustment mechanisms and locking components, the head combines both functions through its geometry and friction surface. This merging reduces the number of parts, simplifies manufacturing, and lowers costs while maintaining positioning precision through the friction-based interface.
Solution Approach 2:
The head structure performs multiple functions: it positions the rod at the desired angle, secures it through friction, and allows for adjustments. This multi-functionality eliminates the need for separate adjustment and locking components, reducing manufacturing complexity and cost while maintaining the required angular positioning precision through the integrated design.
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 improved surgical handling and cost-effective manufacturing by enabling temporary clamping and adjustable angular positioning of the head, allowing for efficient rod alignment and insertion, while maintaining the head in a desired position until final locking.
Implementation Method 1
the pressure element can assume a position within the receiving part in which it clamps the head via the ring by friction without fully locking the head with respect to the receiving part
Data Source
AI summary
A bone anchoring device includes an anchoring element having a shaft and a head, a receiving part having a coaxial bore and a seat for receiving the head, a pressure element configured to be movable within the bore, and a preload element being positionable between the head and the pressure element. When the head is inserted in the receiving part, the head is pivotable with respect to the receiving part, and can be locked at an angle relative to the receiving part by the pressure element. The pressure element can assume a position relative to the receiving part where the pressure element and the preload element are in direct contact, and where the pressure element exerts a force onto the head via the preload element to maintain one of a plurality of releasable angular positions between the head and the receiving part by friction before locking the head.