Spinal Anchor Assembly Retainer Deformation Control
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Solution Overview
Problem
Existing spinal implant fasteners are cumbersome to place and manipulate during surgery due to multiple components, leading to deformation issues that complicate achieving a precise fit between the fastener components and the spinal anatomy.
Innovation Solution
An anchor assembly comprising a receiver member, an anchor member, and a retainer with a pivotally capturing receptacle and axial passages that allow for increased angulation and deformation without compromising the structural integrity, enabling precise positioning and secure fixation of elongated implants along the spinal column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multi-axial screw assemblies with multiple components are used to secure spinal implants, then the anchoring strength and stability are improved, but the complexity of placement and manipulation during surgery increases
Solution Approach 1:
The retainer integrates multiple functions into a single component: it captures the screw head pivotally, provides axial passages for force distribution, and enables multi-planar angulation adjustment. This merging of functions reduces the number of separate components from multiple fastener parts to a unified retainer-screw-implant assembly, directly improving ease of placement while maintaining anchoring strength through the integrated design.
2Reliability
If multiple fastener components are used to achieve precise fit, then the anchoring reliability is improved, but the risk of component deformation during manipulation increases
Solution Approach 1:
The retainer is divided into multiple wall segments that are movable relative to one another about the screw head. This segmentation allows each segment to flex and deform independently during insertion and manipulation, absorbing mechanical stresses that would otherwise deform the entire assembly. The segmented structure maintains anchoring reliability by allowing controlled deformation in non-critical areas while preserving the integrity of the screw-implant connection.
Solution Approach 2:
The axial passages in the retainer body can change their cross-sectional parameters (from open to closed configurations) as the wall segments move relative to each other. This parameter change allows the retainer to adapt its structural properties during manipulation, becoming more flexible during insertion and more rigid when locked in position, thereby preventing unwanted deformation while maintaining reliability.
3Strength
If the retainer structure is made rigid to maintain structural integrity, then the strength is improved, but the ability to accommodate angulation adjustment and deformation is reduced
Solution Approach 1:
The retainer transitions from a static rigid structure to a dynamic system where wall segments can move relative to one another. This dynamic capability allows the retainer to accommodate angulation adjustments in multiple planes as the segments pivot and flex during manipulation. The structural integrity is maintained because the segments are connected through the common screw head and retainer body, creating a unified structure that distributes loads while allowing necessary movements for positioning.
Data Source
AI summary
Anchor assemblies are provided to secure one or more implants along the spinal column that include a retainer in a receiver member. The retainer is configured to distribute the forces exerted on the retainer toward the proximal end of the retainer where it may deform without deforming, distorting or altering the retainer where it supports the anchor member in the receiver member. The desired positioning of the anchor member relative to the retainer and receiver member can thus be attained even when the retainer is subject to deformation forces.