Variable Stiffness Spinal Connecting Element with Uniform Screw Interface
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Solution Overview
Problem
Current spinal implant technologies fail to provide a spinal implant set with varying stiffness along its longitudinal axis that can be used in a wide range of orthopedic situations without requiring predetermined segment lengths or multiple types of bone screws, leading to limitations in multisegmental applications and potential complications during surgery.
Innovation Solution
A spinal implant set with a connecting element whose cross-section varies continuously or in one step along the rod axis, allowing the use of the same bone screws throughout, ensuring compatibility and ease of use during surgery, and featuring a material like PCU with varying stiffness for enhanced biocompatibility and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a metal rod is connected to a textile band in an outer plastic cushion to form a connected dynamic stabilization, then different degrees of stiffness can be achieved, but the structure becomes complex and difficult to manufacture
Solution Approach 1:
The patent applies composite materials by combining a metallic inner rod with a textile band embedded in an outer plastic cushion. This composite structure allows the connecting element to exhibit different degrees of stiffness along its longitudinal axis while maintaining a unified, manufacturable form. The metallic core provides rigidity where needed, while the textile-reinforced plastic cushion provides elasticity in other regions, resolving the contradiction between adaptability and complexity.
2Adaptability or versatility
If variable cross-sections are used to achieve different stiffness areas, then stiffness variation is possible, but the rod requires predetermined segment lengths and multiple screw types for multisegmental applications
Solution Approach 1:
The patent achieves universality by designing a connecting element with variable cross-section that can be used with a single type of bone screw across multiple segments. The rod's varying stiffness profile allows it to serve multiple functions: providing rigidity in fusion areas and flexibility in motion segments, all while accommodating standard bone screw interfaces throughout its length. This eliminates the need for predetermined segment lengths and multiple screw types, resolving the contradiction between stiffness variation and ease of operation.
3Adaptability or versatility
If the cross-section varies along the rod axis to provide different stiffness, then extended orthopedic applications are enabled, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the cross-sectional dimensions of the connecting element along its longitudinal axis. The outer diameter and wall thickness are modified in different regions to create the desired stiffness profile. This controlled parameter variation enables extended orthopedic applications while maintaining manufacturability through established precision manufacturing techniques for variable cross-section components.
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 enables extended application in orthopedic situations by providing a stable and adaptable spinal implant with continuous stiffness variation, facilitating seamless integration with the same bone screws and maintaining long-term stability and biocompatibility, thus addressing the limitations of existing technologies.
Implementation Method 1
elastic connecting rods having different degrees of stiffness along its longitudinal axis
Implementation Method 2
the cross-section varies continuously or in at least one step, preferably exactly one step, along the rod axis
Data Source
AI summary
A connection element (1) for stabilizing vertebral bodies that has a variable stiffness along its longitudinal axis in that particularly the cross-section of the connecting element varies along its longitudinal axis and extends over a plurality of bone screws (6). In spite of the varying cross-section (h1, h2), in a preferred embodiment, the same bone screws (6) may be used in all locations by inserting clamping elements (9, 10) of different lengths.