Pivotal Bone Anchor Assembly with Resilient Ring Positioner Alignment
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Solution Overview
Problem
Existing open-ended bone screws in spinal surgery face challenges with loose or floppy rotation of the receiver, limited angular range, and difficulty in aligning retainers within the receiver, leading to unreliable snap-on connections and inventory management issues due to the need for various sizes and shapes.
Innovation Solution
A pivotal bone screw assembly with a shank, receiver subassembly, pivoting retainer, and multi-purpose positioner that ensures alignment and secure locking, allowing multi-planar or mono-planar motion, and includes a compression insert for stable connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pivoting receiver is used to allow multi-planar motion, then ease of operation is improved, but device complexity increases due to additional alignment components
Solution Approach 1:
A positioner component is introduced as an intermediary element between the receiver and retainer. This positioner ensures proper alignment of the retainer with the shank's capture structure, enabling reliable snap-on connection while maintaining the pivoting capability for multi-planar motion. The positioner acts as a mediator that simplifies the alignment process without compromising the pivoting function.
2Ease of operation
If the retainer is made resilient to facilitate snap-on connection, then ease of operation is improved, but reliability may worsen due to potential misalignment
Solution Approach 1:
The positioner performs a preliminary alignment action before the retainer engages with the shank's capture structure. By pre-positioning the retainer correctly using the positioner's ledged surface, the system ensures that when the resilient retainer is compressed for snap-on connection, it does so in proper alignment, thereby maintaining connection reliability while preserving ease of operation.
3Adaptability or versatility
If multiple receiver configurations are provided for different spinal levels, then adaptability is improved, but device complexity and inventory management worsen
Solution Approach 1:
The positioner is designed with a universal structure that can accommodate different retainer configurations (pivoting and non-pivoting) and work with various receiver types (multi-planar and mono-planar). This universal positioner design allows a single component to serve multiple functions across different spinal application levels, reducing the need for multiple specialized components and simplifying inventory management while maintaining adaptability.
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
The assembly provides reliable, quick, and secure attachment of bone anchors, reducing inventory complexity and ensuring consistent alignment, even in modular spinal systems.
Implementation Method 1
A pivotal bone screw assembly with a shank, receiver subassembly, pivoting retainer, and multi-purpose positioner that ensures alignment and secure locking
Data Source
AI summary
A pivotal bone anchor assembly includes a bone anchor having a capture portion and an anchor portion, and a receiver sub-assembly that includes a resilient open ring positioner, a resilient open ring retainer, and a receiver having an upper portion defining a channel for receiving a rod and a base portion defining a central bore with a recess adjacent to a lower opening. The recess has an upper region and a lower region, with the positioner being disposed within the recess and the retainer being disposed and constrained within the positioner. The retainer and positioner expand together within the upper region of the recess upon the uploading of the capture portion through the lower opening, after which the retainer separates from the positioner to contract and displace downward into the lower region of the recess to capture and hold the bone anchor to the receiver. After the bone anchor is captured, the positioner overlaps the retainer to inhibit the retainer from moving back up into the upper region of the recess.