Ni-Ti Dynamic Bone Anchor with Superelastic Barbs
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Solution Overview
Problem
Existing bone anchors are inadequate for stabilizing weak or osteoporotic bones, as they lack the necessary flexibility and secure fixation to allow controlled motion and prevent loosening.
Innovation Solution
A dynamic bone anchor featuring a nickel-titanium (Ni—Ti) based shape memory alloy with superelastic properties, incorporating a push-and-turn mechanism with barb elements that can be inserted into a bone core hole, allowing for correction and secure anchoring, and a core member that can move relative to the anchor member due to superelastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional rigid bone anchor is used, then strong fixation is achieved, but flexibility and controlled motion are lost
Solution Approach 1:
The patent applies parameter changes by utilizing the superelastic properties of Ni-Ti shape memory alloy to change the mechanical parameters of the anchor member. The material transitions between austenite and martensite phases in response to stress and temperature changes, allowing the anchor to dynamically adjust its stiffness and elasticity. This enables the anchor to provide strong fixation when needed while allowing controlled motion when required, resolving the contradiction between fixation strength and flexibility.
Solution Approach 2:
The patent implements dynamics by creating a dynamic bone anchor system where the anchor member can move relative to the core member along the longitudinal axis. The superelastic anchor member allows for controlled limited motion between the anchor and core, enabling the system to adapt to varying mechanical conditions. This dynamic capability allows the anchor to maintain fixation strength while providing necessary flexibility for controlled motion, directly addressing the technical contradiction.
2Adaptability or versatility
If a dynamic design allowing motion is implemented, then flexibility is improved, but stability and fixation reliability deteriorate
Solution Approach 1:
The superelastic Ni-Ti alloy changes its mechanical parameters dynamically in response to applied stress and temperature. The material exhibits high elasticity and can undergo large deformations while maintaining the ability to return to its original shape. This parameter change capability allows the anchor to provide reliable fixation during stable phases while accommodating controlled motion during dynamic phases, thus maintaining fixation reliability despite the dynamic design.
Solution Approach 2:
The dynamic bone anchor design allows the anchor member to move relative to the core member along the longitudinal axis, providing flexibility. However, the superelastic properties ensure that the anchor member maintains strong engagement with the bone and core member through elastic recovery, preventing loosening. The controlled limited motion is constrained within specific boundaries, ensuring that fixation reliability is maintained while flexibility is provided.
3Strength
If Barb elements are deployed outward for secure anchoring, then fixation strength is improved, but insertion difficulty increases
Solution Approach 1:
The patent applies dynamics by utilizing the superelastic properties of the Ni-Ti alloy to enable the barb elements to change their configuration during insertion. The anchor member can be compressed axially, causing the barb elements to collapse inward, reducing the insertion force required. Once inserted and subjected to tensile stress, the barbs automatically deploy outward to engage with the bone, providing secure anchoring. This dynamic transformation resolves the contradiction between anchoring strength and insertion ease.
Solution Approach 2:
The superelastic material undergoes parameter changes in response to applied stress during insertion. When compressive force is applied during insertion, the material's elastic properties allow the barbs to collapse inward, reducing resistance. After insertion, when tensile load is applied, the material returns to its original shape, deploying the barbs outward to provide strong anchoring. This stress-induced parameter change enables easy insertion while achieving strong fixation.
4Ease of operation
If a push-and-turn mechanism is used for insertion, then insertion ease is improved, but device complexity increases
Solution Approach 1:
The patent merges the push-and-turn insertion mechanism with the superelastic Ni-Ti alloy properties into a single integrated anchor member design. The combination allows the barbs to collapse during pushing while the superelastic material provides the necessary flexibility and recovery. This merging of functions into a single component reduces the number of separate parts and mechanisms required, thereby reducing overall device complexity while maintaining insertion ease.
Solution Approach 2:
The anchor member serves multiple functions: it provides the push-and-turn insertion mechanism, utilizes superelasticity for barb collapse and deployment, and maintains the connection between the head and core member. By making the anchor member multi-functional, the patent reduces the need for separate components for each function, thereby reducing device complexity while achieving easy insertion and secure fixation.
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 dynamic bone anchor provides enhanced stability and flexibility, allowing controlled limited motion of bone parts and vertebrae, preventing loosening while enabling easy insertion and removal, and maintaining fixation through superelastic properties and a strong press-fit connection.
Implementation Method 1
The anchor member is made at least partially of a material that comprises a nickel-titanium (Ni—Ti) based shape memory alloy having superelastic properties
Implementation Method 2
A portion of the anchor member is movable relative to the core member... maintaining fixation through superelastic properties
Data Source
AI summary
A dynamic bone anchor includes an anchor member having a tubular body with a first end and a second end, the anchor member defining an anchor axis including a plurality of barb elements, and being made at least partially of a nickel-titanium (Ni—Ti) based shape memory alloy. The dynamic bone anchor also including a core member configured to be inserted from the first end through the second end such that a first portion of the core number extends out from the first end, and a second portion of the core number extends out from the second end. The anchor member and the core member are configured such that when assembled, the first portion of the core member is spaced apart from the anchor member and movable with respect to it, and the second portion of the core member is fixed to and movable together with the anchor member.