Dynamic Intervertebral Spacer With Cortical Rim Load Sharing
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Solution Overview
Problem
Traditional interbody spinal implants face challenges such as end-plate preparation, implant retention, implant subsidence, bone graft volume, incorporation with vertebral bone, and radiographic visualization, particularly due to improper seating on the apophyseal rim of the vertebral body, which is composed of stronger cortical bone.
Innovation Solution
The intervertebral spacer implant features a body with lobes extending from the perimeter, allowing it to flex and engage the apophyseal rim, reducing subsidence risk, and includes anti-migration features and radiographic markers for improved stability and visualization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional threaded cylindrical implants are used, then implantation is straightforward, but the implant contacts only a small portion of the vertebral endplate and engages softer cancellous bone, increasing subsidence risk
Solution Approach 1:
The implant body is divided into multiple load-bearing surfaces or zones, including a first load-bearing surface for initial engagement and a second load-bearing surface for enhanced cortical bone contact. This segmentation allows the implant to distribute loads across different regions of the vertebral endplate, improving retention while maintaining ease of implantation.
Solution Approach 2:
The implant transitions from traditional point or line contact to surface contact with the vertebral endplate. The first and second load-bearing surfaces create multiple contact zones, effectively adding dimensional coverage from point/line contact to area contact, thereby improving load distribution and reducing subsidence risk.
2Ease of operation
If traditional implants engage the center of the vertebra, then implantation is easier, but they contact softer cancellous bone rather than stronger cortical bone, increasing apparent stress and subsidence risk
Solution Approach 1:
Different regions of the implant are designed with different functional qualities. The first load-bearing surface is optimized for initial engagement and load distribution, while the second load-bearing surface is specifically designed to contact the stronger cortical bone at the periphery. This local differentiation allows the implant to leverage the superior strength of cortical bone while maintaining ease of implantation.
3Strength
If the implant uses a rigid structure, then it provides strong load-bearing capacity, but it increases overall stiffness and prevents bone graft material from carrying load
Solution Approach 1:
The implant incorporates dynamic elements that allow it to adapt its stiffness characteristics. The structure can transition between more rigid and more compliant states, enabling the bone graft material to carry a portion of the load during the healing process while maintaining adequate load-bearing capacity. This dynamic adaptability supports both the implant's structural requirements and the bone graft's load-bearing potential.
4Device complexity
If the implant contacts a small area of the endplate, then the structure is simpler, but the stress concentration increases and subsidence risk increases
Solution Approach 1:
The implant combines multiple load-bearing surfaces and contact zones into a unified structure. The first and second load-bearing surfaces work together to distribute loads across a larger area of the vertebral endplate, reducing stress concentration while maintaining structural simplicity. This merging of contact zones effectively increases the load-bearing area without significantly complicating the implant design.
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 implant enhances end-plate preparation, reduces subsidence, increases bone graft volume, improves retention, and facilitates better radiographic assessment by distributing load to the cortical bone rim and incorporating with the vertebral bone.
Implementation Method 1
the at least one lobe is adapted to flex when the intervertebral spacer is implanted adjacent a vertebral body
Data Source
AI summary
Intervertebral spacer implants with dynamic load spreading features responsive to external loads and having attachment mechanisms. The dynamic load spreading features having a native state and a loaded state, which complements vertebral end plate geometry and disperses load to the epiphyseal rim.