Polyaxial Bone Screw with Elastic Coil Connecting Member
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional spinal stabilization methods, such as fusion and rigid longitudinal connecting members, lead to immobilization of the spine, rapid degeneration, and inadequate pain relief, while dynamic stabilization approaches face challenges in providing adequate spinal support and fatigue strength.
Innovation Solution
The development of polyaxial bone screw assemblies with an elastic and flexible longitudinal connecting member, comprising an inner cylindrical core and an outer coil-like member, allowing for sliding and torsional engagement, along with adjustable support structures and coatings for enhanced stability and bioactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fusion and rigid longitudinal connecting members are used for spinal stabilization, then spinal stability is improved, but spinal mobility is lost and adjacent segments degenerate rapidly
Solution Approach 1:
The patent applies the dynamics principle by transitioning from rigid, fixed connecting members to a dynamic system with an elastic core and flexible coil-like member that allows controlled movement. The elastic core provides stability while the flexible member enables natural spinal motion, resolving the contradiction between stability and mobility by making the system adaptable rather than static.
Solution Approach 2:
The patent changes the mechanical parameters of the connecting member by using an elastic core with specific modulus values and a flexible coil-like member with controlled stiffness. This allows the system to maintain stability through material property optimization while permitting physiological motion, thereby resolving the stability-mobility contradiction through parameter adjustment rather than structural rigidity.
2Strength
If rigid longitudinal connecting members are used, then spinal support is adequate, but fatigue strength is insufficient and implant failure risk increases
Solution Approach 1:
The patent applies composite materials by combining an elastic core (made of materials with specific modulus values) with a flexible coil-like member. This composite structure distributes mechanical loads across different material properties, providing adequate spinal support through the elastic core while the flexible member absorbs fatigue cycles, thereby improving reliability without sacrificing strength.
Solution Approach 2:
The patent segments the connecting member into distinct functional components: an elastic core for primary load-bearing and support, and a flexible coil-like member for fatigue resistance and motion accommodation. This segmentation allows each component to optimize its specific function, with the core providing strength and the flexible member providing fatigue durability.
3Ease of operation
If dynamic stabilization with flexible members is used, then spinal mobility is maintained, but spinal support becomes inadequate
Solution Approach 1:
The patent applies the nested doll principle by placing the elastic core inside the flexible coil-like member, with the core providing primary structural support and the outer flexible member providing motion capability. This nested configuration allows the stiffer inner core to maintain spinal support while the outer flexible layer permits natural mobility, resolving the support-mobility contradiction through hierarchical structuring.
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 dynamic, protected motion of the spine, offering improved spinal support, reduced risk of implant failure, and potential for natural movement, while maintaining stability and preventing tissue ingrowth.
Implementation Method 1
an elastic and flexible longitudinal connecting member, comprising an inner cylindrical core and an outer coil-like member, allowing for sliding and torsional engagement
Data Source
AI summary
A pivotal bone screw assembly includes a receiver having a central bore with a bottom opening and a channel for receiving an elongate rod, with the central bore including a partial spherical internal surface adjacent the bottom opening and a horizontally-extending recess with a cylindrical sidewall surface. The assembly also includes a shank with a capture structure for positioning within the central bore and an anchor portion for attachment to the bone, with the capture structure having a partial spherical lower surface configured to slidably engage the internal surface of the central bore to provide for pivotal motion of the shank with respect to the receiver, together with an insert with a rod seating surface and an outwardly-projecting radiused structure, with the insert being downwardly displaceable within the central bore until the radiused structure snaps into the recess to prevent upward movement of the insert with respect to the receiver.