Intervertebral Disc Replacement With Variable Spring Constant Columns
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Solution Overview
Problem
Current intervertebral disc replacements often reduce compressive support, overload adjacent facet joints, and generate excessive wear particles, leading to premature arthritic changes and surgical complications.
Innovation Solution
A three-layer intervertebral disc replacement with compressible column springs having varying spring constants, arranged in concentric rings and designed to mimic the biomechanical properties of a native disc, including compressive, extension, and rotational behavior, manufactured using 3D printing for patient-specific customization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If existing intervertebral disc replacements are used, then spinal motion is maintained, but compressive support is reduced and facet joints are overloaded
Solution Approach 1:
The disc replacement incorporates multiple column springs with different spring constants (K values) distributed throughout the structure. Each spring can be tailored with specific stiffness characteristics to match the load-bearing requirements of different spinal regions, providing localized optimization of compressive support while distributing forces appropriately to prevent facet joint overload.
Solution Approach 2:
The invention utilizes variable spring constants across different columns and within individual springs (through varying coil densities or materials) to dynamically adjust the mechanical response of the disc replacement. This parameter variation allows the device to provide appropriate compressive support across different loading conditions while maintaining physiological force distribution patterns.
2Stability of the object's composition
If existing intervertebral disc replacements are used, then spinal stability is provided, but excessive wear particles are generated
Solution Approach 1:
The invention replaces traditional bearing surface mechanics with a spring-based mechanical system. Instead of relying on articulating surfaces that generate wear particles through friction and contact, the disc replacement uses elastic deformation of column springs to absorb and dissipate mechanical energy, thereby eliminating the wear particle generation mechanism while maintaining spinal stability.
Solution Approach 2:
The column springs are designed as sacrificial elements that can undergo controlled deformation and energy absorption. The springs are engineered to deform in a predictable manner under load, absorbing mechanical energy that would otherwise be transmitted to bearing surfaces and generate wear. This approach trades the 'life' of the spring material for the protection of the surrounding spinal structures from wear-induced damage.
3Ease of manufacture
If uniform spring constants are used in all column springs, then manufacturing is simplified, but biomechanical accuracy is reduced
Solution Approach 1:
The disc replacement is divided into multiple independent column spring units, each capable of having different spring constants. This segmentation allows the complex biomechanical requirements of the spinal disc to be broken down into discrete, manufacturable elements. Each column can be manufactured with specific K values using additive manufacturing techniques, enabling precise control of the overall mechanical behavior while maintaining manufacturing feasibility through modular construction.
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 disc replacement provides improved compressive and shear stress dampening, reduces facet and adjacent level disc disease, minimizes wear debris, and allows for precise spinal motion parameters, reducing the risk of osteolysis and chronic inflammation, while maintaining spinal flexibility and stability.
Implementation Method 1
a second layer coupled to the first layer, the second layer comprising a plurality of compressible column springs, where each of the plurality of compressible column springs includes a plurality of stacked coils, and each of the plurality of stacked coils has a spring constant (K)
Implementation Method 2
Each of the plurality of compressible column springs includes a plurality of stacked coils, and each of the plurality of stacked coils has a spring constant (K)
Implementation Method 3
manufactured using 3D printing for patient-specific customization
Data Source
AI summary
According to some embodiments of the invention, an intervertebral disc replacement includes a first layer having a lower surface for contacting a first vertebral bone, a second layer coupled to the first layer, the second layer comprising a plurality of compressible column springs, and a third layer coupled to the second layer, the third layer having an upper surface for contacting a second vertebral bone. Each of the plurality of compressible column springs comprises a plurality of stacked coils, and each of the plurality of stacked coils has a spring constant (K). At least one of the plurality of compressible column springs includes a first coil having a first spring constant and a second coil comprising a second spring constant, wherein the first spring constant is different from the second spring constant.