Convex Spinal Fusion Interbody Spacer Design
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Solution Overview
Problem
Existing interbody devices for spinal fusion often fail to engage sufficient bone surface area, leading to subsidence and require extensive vertebral reshaping, while cylindrical devices are not well-suited to conform to the natural concave shape of vertebrae, and do not effectively promote normal lordosis.
Innovation Solution
A non-threaded, non-cylindrical interbody device with convex upper and lower surfaces and concave sides, designed to conform to the natural concavity of vertebrae, minimizing subsidence and promoting fusion by maximizing bone contact and allowing for efficient packing of bone fusion material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cylindrical threaded interbody devices are used, then the device can be directly threaded between vertebrae, but the device engages insufficient bone surface area leading to subsidence
Solution Approach 1:
The patent inverts the conventional approach by making the interbody device convex rather than concave, and non-threaded rather than threaded. This inversion allows the device to seat against the natural concave surfaces of vertebral end plates, maximizing bone contact area without requiring threading operations, thus resolving the contradiction between ease of implantation and bone engagement stability
Solution Approach 2:
The patent applies curvature by designing the interbody device with convex surfaces that conform to the natural concave geometry of vertebral end plates. This curved surface design maximizes the contact area between the device and bone, distributing loads more effectively and preventing subsidence, thereby improving reliability while maintaining ease of implantation
2Reliability
If interbody devices are designed to maximize bone contact surface, then subsidence is reduced, but the device volume and weight increase
Solution Approach 1:
The patent applies local quality by concentrating the device's mass and structural reinforcement only where needed to maintain strength, rather than uniformly increasing the entire device. The convex geometry and strategic material distribution allow sufficient bone contact for stability while minimizing overall volume and weight
Solution Approach 2:
The patent employs composite materials that provide high strength-to-weight ratio, enabling the device to achieve adequate bone contact surface area for stability without proportionally increasing weight. The composite construction allows optimization of local structural properties to maintain reliability while controlling overall mass
3Reliability
If conventional interbody devices are used, then fusion can be promoted, but extensive cutting and reshaping of vertebrae is required
Solution Approach 1:
The patent inverts the conventional approach by designing a convex device that seats against the natural concave vertebral surfaces, eliminating the need for extensive bone resection or reshaping. This inversion allows the device to conform to the existing bone geometry, reducing surgical preparation complexity while maintaining fusion promotion capability
Solution Approach 2:
The patent changes the geometric parameters of the interbody device from concave/threaded to convex/non-threaded, allowing it to interface with the natural concave geometry of vertebral end plates. This parameter change eliminates the need for extensive bone cutting and reshaping while preserving the device's ability to promote fusion through maintained spacing and stability
4Weight of moving object
If the device is made smaller and lighter, then body compatibility is improved, but strength is reduced
Solution Approach 1:
The patent employs composite materials with high strength-to-weight ratios, enabling the device to be made smaller and lighter while maintaining adequate structural strength. The composite construction allows optimization of material properties to achieve the necessary strength performance at reduced mass
Solution Approach 2:
The patent applies local quality by concentrating structural reinforcement and material density only in critical load-bearing regions, rather than uniformly throughout the device. This localized optimization maintains strength where needed while minimizing overall weight and volume for improved body compatibility
Data Source
AI summary
A convex spinal fusion interbody space device includes spaced apart superior and inferior abutment surfaces which are effectively medially convex. The peak of such convexity is displaced anteriorly of a central plane through the device. The spacer device has a height which is greater than the width of the device. The spacer device is implanted between a pair of adjacent vertebrae by insertion in a tipped-over orientation and then reoriented to an upright orientation for engagement by facing surfaces of the vertebrae. Fusion promoting bone material is packed between the vertebrae and about and within the spacer device subsequent to implantation.