Spinal Anchor Assembly Smooth Rod Pathway Wear Reduction
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Solution Overview
Problem
Current spinal implants face issues with wear and friction, particularly due to interrupted rod surfaces and access apertures that cause rod wear and head wear during sliding motion, leading to reduced durability and effectiveness.
Innovation Solution
The design incorporates a polyaxial spinal anchor assembly with a smooth and continuous rod pathway, a tulip head with flexible coupling, and interlocking features to minimize friction and prevent splaying, along with a set screw mechanism to secure the rod retainer, ensuring reduced wear and improved sliding motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If access apertures are provided in the rod pathway for tool access, then ease of operation is improved, but rod wear and head wear increase due to interrupted surfaces
Solution Approach 1:
The rod pathway is segmented into an upper portion and a lower portion that can be independently configured. The upper rod pathway includes apertures for tool access, while the lower rod pathway maintains a continuous smooth surface for rod sliding, resolving the contradiction by dividing the pathway into functional segments with different surface characteristics
Solution Approach 2:
A rod retainer is introduced as an intermediary component between the head and the rod. The rod retainer includes a retainer body with a smooth continuous retainer pathway that mediates between the apertured upper pathway and the rod, preventing direct contact between the rod and the apertured surfaces, thereby reducing wear while maintaining tool access capability
2Reliability
If a smooth continuous rod pathway is used, then wear is reduced, but access to internal features becomes more difficult
Solution Approach 1:
The rod pathway is segmented into upper and lower portions with different surface characteristics. The upper portion has apertures for tool access, while the lower portion maintains continuity for smooth rod sliding, allowing both wear reduction and ease of operation in different regions
Solution Approach 2:
The design transitions from a two-dimensional continuous surface to a three-dimensional structure with apertures in the upper portion. This dimensional change allows tool access through the apertures while maintaining the continuous smooth surface in the lower portion for rod sliding, resolving the contradiction through spatial differentiation
3Ease of operation
If the rod pathway is interrupted for apertures, then tool access is enabled, but frictional capture increases during sliding motion
Solution Approach 1:
The rod retainer acts as a mediator between the apertured upper pathway and the rod. The smooth continuous retainer pathway in the rod retainer body provides a low-friction interface for rod sliding, eliminating direct frictional contact with the apertured surfaces while still allowing tool access through the apertures
Solution Approach 2:
The harmful frictional contact is extracted from the rod pathway by introducing the rod retainer with its own smooth retainer pathway. This separates the tool access function (apertures in upper pathway) from the sliding function (smooth retainer pathway), eliminating frictional capture while maintaining both capabilities
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 solution significantly reduces rod and head wear, enhances durability, and allows for polyaxial motion, accommodating bent rods while maintaining stability and minimizing frictional capture, thereby improving the longevity and functionality of spinal implants.
Implementation Method 1
a flexible coupling wire that allows polyaxial motion between the head and the bone connector
Implementation Method 2
a set screw mechanism to secure the rod retainer
Data Source
AI summary
One embodiment of an implantable anchor assembly for support of a spinal rod includes a bone connector; a head having first and second opposing arms and forming a lower rod pathway therebetween, each said first and second opposing arm having the same one of a notch or a projection, the one of a notch or projection of said first arm facing one of a notch or projection of said second arm; a rod retainer having third and fourth opposing arms and forming an upper rod pathway therebetween, each said third and fourth opposing arm having the other of a notch or a projection, said third and fourth opposing arms being slidable to a position between said first and second opposing arms, said rod retainer having a threaded aperture; and a set screw threadably receivable within the threaded aperture.