Spinal Bushing Friction Reduction via Material Substitution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spinal rod anchoring systems using metallic bushings can result in metal particles being deposited in patients due to friction, and there is a need for a solution that allows for axial movement and rotational flexibility while minimizing tissue irritation and debris generation.
Innovation Solution
The use of polymeric, ceramic, or cobalt-chromium bushings with low-friction coatings or materials, integrated or separable within a tulip-type anchoring head, which permits axial movement and rotational flexibility (roll, pitch, and yaw) without compressing the rod excessively, and includes retention mechanisms like set screws and flexible connectors to secure the bushing in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic bushings are used in spinal rod anchoring systems, then structural strength and durability are improved, but metal particles are deposited in patients due to friction
Solution Approach 1:
The patent introduces a bushing as an intermediary component between the metallic spinal rod and the anchoring system. This bushing, made of low-friction material (polymer, ceramic, or coated metal), mediates the contact interface to prevent direct metal-to-metal friction, thereby eliminating metal particle deposition while maintaining structural integrity.
Solution Approach 2:
The patent replaces the traditional metallic contact interface with alternative materials that have superior low-friction properties. By substituting metal-to-metal mechanical contact with metal-to-polymer/ceramic/coated contact, the system eliminates the harmful friction-based metal particle generation while preserving the mechanical function of the anchoring system.
2Object-affected harmful factors
If low-friction bushings are used to permit axial movement and rotational flexibility, then tissue irritation and debris generation are minimized, but structural support and stability may be compromised
Solution Approach 1:
The patent employs composite material structures where the bushing is integrated with or attached to the metallic anchoring components. This composite approach combines the low-friction, biocompatible properties of polymers/ceramics with the structural strength of metals, allowing the system to provide both movement flexibility and reliable structural support simultaneously.
Solution Approach 2:
The patent modifies the friction parameter of the contact interface by introducing low-friction materials, while maintaining other critical parameters such as load-bearing capacity and structural stability through proper design of the bushing-rod and bushing-anchor interfaces. The system achieves controlled movement within specific parameter ranges while preserving overall structural reliability.
3Object-generated harmful factors
If polymeric or ceramic bushings are used instead of metallic bushings, then metal particle deposition is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the anchoring system into distinct functional components: the metallic rod, the bushing (made of polymer/ceramic/coated material), and the anchoring mechanism. This segmentation allows each component to be manufactured using optimal processes for its material and function, then assembled together, thereby managing manufacturing complexity through modular design rather than requiring complex monolithic manufacturing.
Solution Approach 2:
The patent implements a nested structure where the bushing is inserted into or integrated with the metallic anchoring components. The bushing is nested within the anchoring system's structural framework, allowing for simplified assembly where components are fitted together in a hierarchical manner, reducing overall manufacturing complexity despite using multiple material types.
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
This solution reduces metal particle deposition, allows for effective axial and rotational movement of spinal rods, minimizes tissue irritation, and reduces debris generation, providing a more biologically acceptable and efficient anchoring system for spinal procedures.
Implementation Method 1
a low-friction bushing that comes into contact with a spinal rod... fabricated from a hard, low-friction, biologically acceptable material
Data Source
AI summary
Various methods and apparatus for dynamic stabilization of bones, and especially of vertebra. Disclosed herein are bushings that permit axial movement of a rod, tether, or similar interconnection device relative to an anchoring head that is coupled to a bone. Some bushings further allow lateral relative movement or rotational relative movement, such additional relative movement being limited by the size and shape of the bushing, the size and shape of the interconnection device, the size and shape of the bushing container, the manner of attaching the anchoring head to the bone, or other considerations.