Bone Anchor Shape Memory Alloy Thermal Expansion
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Solution Overview
Problem
Existing bone anchors face challenges with high insertion forces and bone trauma due to the need for pre-drilled holes and mechanical activation, which can cause damage and reduce holding power, especially with barb-type and expandable casing-type anchors.
Innovation Solution
The use of temperature-activated shape memory alloy engagement elements that transition from a retracted to an expanded configuration within the bone, reducing insertion forces and allowing for self-embedding without pre-drilled holes, and providing better gripping with smaller hole sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barb-type or expandable casing-type bone anchors are pressed into pre-drilled holes, then the bone anchor can be secured in the bone, but high insertion forces are required and significant bone trauma occurs
Solution Approach 1:
The patent changes the activation parameter from mechanical force to temperature. The engagement elements are made of shape memory alloy that transitions from martensitic to austenitic phase at body temperature, causing automatic expansion without requiring high insertion forces or pre-drilled holes, thus reducing bone trauma while maintaining holding power
Solution Approach 2:
The patent replaces the mechanical activation system (where barbs are folded inward and require high insertion forces) with a thermal activation system. The shape memory alloy elements automatically expand at body temperature, eliminating the need for pre-drilled holes and reducing insertion forces and bone trauma
2Ease of operation
If barbs are sheathed in a tube prior to insertion, then the bone anchor assumes a streamlined geometry for easier insertion, but significant friction is created during sheath withdrawal requiring substantial effort to release the barbs
Solution Approach 1:
The patent replaces mechanical barb deployment (requiring sheath withdrawal and high release forces) with thermal activation. The shape memory alloy elements automatically expand at body temperature, eliminating the sheath and associated friction problems, allowing easy insertion without streamlined geometry while maintaining easy release
Solution Approach 2:
The patent extracts and eliminates the sheath component from the bone anchor system. By using temperature-activated shape memory alloy elements that automatically expand at body temperature, the sheath is no longer needed, removing the source of friction and release force problems
3Ease of operation
If larger bone holes are used to reduce insertion forces, then easier insertion is achieved, but the holding power of the anchor is reduced and bone trauma increases
Solution Approach 1:
The patent changes the activation parameter from mechanical insertion force to thermal activation at body temperature. The shape memory alloy elements expand automatically after insertion, allowing use of smaller bone holes that maintain both ease of insertion and holding power while reducing bone trauma
Solution Approach 2:
The patent performs the expansion action automatically at body temperature after insertion. The shape memory alloy elements are designed to transition from martensitic to austenitic phase at physiological temperature, causing automatic expansion to engage the bone wall without requiring large insertion forces or holes
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
This approach significantly reduces insertion complications, enhances holding power, and minimizes bone trauma by utilizing thermal transformation of shape memory alloys to deploy engagement elements radially outward, facilitating easier insertion and higher pull-out forces.
Implementation Method 1
the engagement elements are formed from a shape memory alloy and have a martensitic start temperature (Ms) and an austenitic finish temperature (Af) less than a physiological temperature of a human body
Implementation Method 2
thermal transformation of shape memory alloys to deploy engagement elements radially outward
Data Source
Figure 1~2
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Figure 5
AI summary
A bone anchor (20) that uses temperature transition of a shape memory material to expand the anchor within a bone. Thermal transformation of the metallic crystal state (and hence the stress/strain properties) of shape memory alloy (e.g., Nitinol, NiTi) expands engagement elements (32) within the bone to fix the bone anchor in place. Various self-locking assemblies (60) for attached suture material to the bone anchor are also disclosed.