Polyaxial Bone Anchoring Device Sequential Locking Mechanism
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Solution Overview
Problem
Current polyaxial bone anchoring devices require complex handling and multiple tools for simultaneous locking of the head and rod, making the fixation process cumbersome and prone to errors.
Innovation Solution
A polyaxial bone anchoring device with a sequential locking mechanism using a single tool with a single drive portion, allowing for independent locking of the head and rod, facilitated by a deformable pressure member and a monolithic locking member that clamps the head and rod in a sequential manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single tool with a single drive portion is used for sequential locking, then the ease of operation is improved, but the device complexity increases due to the deformable pressure member mechanism
Solution Approach 1:
The deformable pressure member automatically performs the clamping function when the locking member is advanced, eliminating the need for separate manual clamping operations. The system uses itself to achieve both clamping and locking through a single tool operation.
Solution Approach 2:
The pressure member transitions from a rigid state to a deformable state under load, changing its physical parameters to enable sequential clamping. This parameter change allows the same component to adapt its function based on the applied force level.
2Reliability
If multiple locking elements are used for independent locking of head and rod, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The locking member integrates multiple functions: it simultaneously provides clamping force through the pressure member and locking force through direct engagement with the rod. This merging of functions reduces the number of separate components while maintaining reliability.
Solution Approach 2:
The single locking member serves multiple purposes: it acts as both a clamping mechanism (via the pressure member) and a locking mechanism (via direct rod engagement). This multi-functionality eliminates the need for separate locking elements for each component.
3Productivity
If simultaneous locking of head and rod is performed, then the productivity is improved, but the ease of operation deteriorates due to requiring tools with multiple drive portions
Solution Approach 1:
The sequential locking process maintains continuous useful action through a single uninterrupted tool operation. The same single drive portion tool continues to advance the locking member throughout both clamping and locking phases, eliminating tool changes or repositioning.
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
Simplifies the handling and fixation process, enabling reliable and adjustable locking of the head and rod with fewer parts, enhancing ease of use and reducing the complexity of the fixation process.
Implementation Method 1
the locking member contacts the pressure member such that the deformable portion is deformed and the locking member comes into contact with the rod and clamps the rod
Implementation Method 2
the locking member contacts the pressure member resulting in a load applied to the pressure member that clamps the head
Data Source
AI summary
A polyaxial bone anchoring device is provided comprising a bone anchoring element having a shank to be anchored in a bone and a head; a receiving part coupled to the shank and configured to pivotably receive the head, and having a channel for receiving a rod and a longitudinal axis; a pressure member configured to be positioned in the receiving part; a locking member insertable into the channel; wherein the pressure member has a deformable portion; and wherein, when the locking member is advanced into the channel in the direction of the longitudinal axis, the locking member in moveable from a position where it contacts the pressure member resulting in a load applied to the pressure member that clamps the head, to a position where the locking member contacts the pressure member such that the deformable portion is deformed and the locking member contacts the rod and clamps the rod.