Asymmetric Radius Intervertebral Implant Core Kinematics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing intervertebral implants with spherical bearing surfaces and sockets of equal radius suffer from undefined kinematics and excessive translational movement during pivoting, which can lead to improper vertebral body alignment and increased wear, especially under high forces from ligaments and muscles.
Innovation Solution
Designing an intervertebral implant with bearing surfaces and sockets of differing radii, where one side has a significantly larger radius to restrict movement and ensure a defined pivoting sequence, reducing unwanted translation by using a core with spherically curved surfaces that engage in corresponding sockets, and incorporating lateral guiding surfaces and stops to limit pivoting to a single direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spherical bearing surfaces and sockets of equal radius are used, then pivoting movement is achieved, but undefined kinematics and excessive translational movement occur
Solution Approach 1:
The patent applies asymmetry by using spherical bearing surfaces and sockets with different radii on opposing sides of the core. Specifically, one side has a smaller radius while the other has a larger radius, creating asymmetric geometry that constrains the movement path and eliminates undefined kinematics, ensuring only pivoting movement occurs without unwanted translation.
Solution Approach 2:
The patent applies local quality by differentiating the bearing surface and socket radii at specific locations on the core. The smaller radius is positioned at one end while the larger radius is at the other end, creating localized constraints that control the movement characteristics in different regions of the implant.
2Adaptability or versatility
If a plane bearing surface is used on one side, then lateral movement is allowed to compensate for translation, but the core may be driven laterally out of position under high forces
Solution Approach 1:
The patent replaces the plane bearing surface with a spherical bearing surface of larger radius on one side, maintaining the ability to accommodate movement while preventing lateral displacement. The asymmetric radius configuration ensures the core remains constrained within the bearing sockets under high clamping forces from ligaments and muscles.
3Ease of operation
If the core moves on a plane bearing surface, then lateral compensation is possible, but undesired translational movement increases
Solution Approach 1:
The patent uses spherical bearing surfaces with different radii instead of a plane bearing surface. The curvature of the spherical surfaces, particularly the larger radius on one side, guides the core movement along a controlled arc path that eliminates linear translation while allowing necessary pivoting motion, thereby removing the harmful translational movement component.
Data Source
AI summary
In an intervertebral implant with a top contacting element, a bottom contacting element and arranged between these a core which with an upper, spherical bearing surface engages a spherical bearing socket, having the same radius, of the top contacting element and with a lower, spherical bearing surface engages a spherical bearing socket, having the same radius, of the bottom contacting element, in order to improve the kinematics and the endurance, it is proposed that the radius of the bearing surface and of the bearing socket receiving it differ on opposing sides of the core at least by the factor 5.