Fillable Nuclear Disc Implant for Modulus-Matched Load Damping
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Solution Overview
Problem
Existing methods for implanting a nuclear prosthesis in situ fail to address the substantial difference in modulus of elasticity between vertebral bony elements and implanted materials, leading to issues like subsidence, migration, and expulsion of the implant, and do not effectively dampen impacts or sudden increases in intradiscal pressure.
Innovation Solution
A kit comprising an inner and outer fillable enclosure with a reinforcing band, an inflation stylus, and a delivery sheath, allowing for minimally invasive implantation and inflation of the enclosures with a curable medium, ensuring a compliant modulus of elasticity that matches the surrounding tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nuclear prosthesis is implanted using existing in situ formation techniques, then the implant can be placed in the disc space, but the high modulus of elasticity of the implanted material causes it to fail to dampen impacts and sudden increases in intradiscal pressure
Solution Approach 1:
The patent changes the physical state and mechanical properties of the implant material by using a flowable curable material that transitions from a low-viscosity liquid to a solid gel or rubbery state after implantation. This parameter change allows the material to achieve both low initial modulus for impact damping and sufficient final strength for structural support, resolving the contradiction between impact damping capability and structural strength.
Solution Approach 2:
The patent employs composite material systems consisting of a curable base material combined with reinforcing agents or fillers that provide both compliance for impact absorption and structural integrity. The composite formulation allows tuning of the modulus of elasticity to match native disc tissue properties, simultaneously achieving impact damping and preventing subsidence.
2Strength
If a nuclear prosthesis with high modulus of elasticity is implanted, then structural support is provided, but the large difference in modulus of elasticity between implanted material and adjacent tissues leads to softening of vertebral end plates and subsidence of the implant
Solution Approach 1:
The patent modifies the mechanical parameters of the implant material to achieve a modulus of elasticity that closely matches native disc tissue and vertebral end plate properties. This parameter matching prevents stress shielding and bone softening while maintaining sufficient structural support, thereby preventing subsidence while providing necessary structural integrity.
3Reliability
If a nuclear prosthesis is implanted using existing techniques, then the implant is placed in the disc space, but migration and expulsion of the implant occur due to mismatch in mechanical properties
Solution Approach 1:
The patent adjusts the modulus of elasticity and other mechanical parameters of the implant material to closely match the surrounding disc and vertebral tissues. This mechanical property matching ensures uniform stress distribution during loading, preventing implant migration and expulsion while maintaining implant stability and long-term reliability.
4Ease of operation
If a flowable curable material is delivered into a mold to form a nuclear prosthesis, then the implant can be formed in situ, but the substantial difference in modulus of elasticity between implanted material and vertebral elements causes biomechanical incompatibility
Solution Approach 1:
The patent utilizes the ability to change physical and mechanical parameters of the curable material both before and after implantation. The material is delivered in a flowable state for ease of injection and in situ formation, then cures to achieve optimal mechanical properties for biomechanical compatibility, thereby resolving the contradiction between ease of implantation and biomechanical compatibility.
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 a nuclear implant that maintains biomechanical mobility, prevents subsidence, and encourages tissue integration, effectively absorbing vertical and horizontal load stresses while minimizing migration and expulsion.
Implementation Method 1
delivering the flowable curable material into the mold to fill the cavity, and (iv) permitting the curable material to cure
Data Source
AI summary
A nuclear disc implant includes an inner fillable enclosure and an outer fillable enclosure. After insertion into a enucleated disc cavity, the inner enclosure is filled with a fluid and the outer fillable enclosure is filled with a curable material. The curable material is allowed to cure and the fluid is removed from the inner enclosure to leave an inner enclosure surrounded by an cured outer enclosure. A reinforcing band may be provided around the nuclear disc implant. An inflation tool to fill the nuclear disc implant is provided.