Dynamic Spinal Connector With Segmented Rod And Cord
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Solution Overview
Problem
Current spinal stabilization methods face challenges in providing adequate fatigue strength and natural movement of the spine without fusion, as well as compatibility with rigid rod systems, especially in situations requiring varying levels of rigidity and flexibility along the spine.
Innovation Solution
A dynamic longitudinal connecting member comprising a rigid rod portion and a flexible cord portion, covered by a flexible jacket, which can be adjusted in length and tensioned for optimal spinal support, allowing for both rigid and dynamic stabilization depending on the spinal segment's needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid longitudinal connecting member is used to provide substantial immobilization and support, then spinal stability and structural integrity are improved, but natural spinal movement and flexibility are lost
Solution Approach 1:
The connecting member is divided into distinct segments: a rigid rod portion for structural support and a flexible cord portion for allowing movement. This segmentation enables different regions of the same device to provide different functions, resolving the contradiction between stability and flexibility.
Solution Approach 2:
Different portions of the connecting member have different mechanical properties - the rod portion is rigid while the cord portion is flexible. This local differentiation of quality allows the device to simultaneously provide both structural integrity and natural movement capability at different locations.
2Adaptability or versatility
If a flexible cord portion is used to allow natural spinal movement, then adaptability and motion are improved, but fatigue strength and structural support are reduced
Solution Approach 1:
The device separates the functions of movement allowance and fatigue resistance into different segments - the flexible cord handles motion while the rigid rod provides fatigue strength, eliminating the need for the entire device to compromise on either property.
Solution Approach 2:
The connecting member combines materials with different mechanical properties - rigid materials for the rod portion and flexible materials for the cord portion - creating a composite structure that exhibits both flexibility and high fatigue strength simultaneously.
3Strength
If fusion is performed to provide permanent immobilization and prevent anchor loosening, then long-term spinal stability is improved, but adjacent spinal segments experience increased stress and accelerated degeneration
Solution Approach 1:
The device transitions from static immobilization (fusion) to dynamic stabilization, allowing controlled motion at the instrumented level while maintaining stability. This dynamic approach redistributes stresses more evenly, preventing the hyper-mobility and collapse that occur with fusion.
Solution Approach 2:
The device changes the mechanical parameters of the spinal construct by introducing a flexible element that allows controlled deformation and stress distribution, altering how loads are transmitted through the spine and reducing peak stresses at adjacent segments.
4Ease of manufacture
If a uniform rigid rod is used throughout the entire length, then manufacturing simplicity is maintained, but the ability to provide varying levels of support along different spinal segments is lost
Solution Approach 1:
The connecting member is manufactured as segmented components (rod and cord portions) that can be produced using relatively simple processes, then assembled together. This segmentation allows each component to be optimized for its specific function while maintaining manufacturing feasibility.
Solution Approach 2:
The device introduces dynamic adaptability through the flexible cord portion that can adjust to varying spinal segment requirements, allowing the same basic device design to accommodate different clinical scenarios without complex customization.
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 provides enhanced spinal stabilization with improved fatigue strength and flexibility, allowing for natural movement while maintaining structural integrity, and is compatible with existing rigid rod systems, addressing the limitations of both fusion and traditional dynamic stabilization methods.
Implementation Method 1
an elastic bumper in compression
Implementation Method 2
a flexible cord portion... allowing for both rigid and dynamic stabilization
Data Source
AI summary
A medical implant assembly having at least two bone attachment structures cooperating with a dynamic longitudinal connecting member, the improvement wherein the connecting member includes: a first end, a transition portion, and a second end; a substantially rod portion extending longitudinally from the first end to the transition portion, and including a longitudinal axis and a substantially rigid core running substantially parallel with the longitudinal axis; a substantially cord portion joined with the rod portion and extending from the transition portion to the second end; and a substantially flexible jacket portion covering the rod and cord portions.