Intramedullary Nail Shape Memory Alloy Bone Fusion
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Solution Overview
Problem
Current bone fixation techniques for ankle fusion, such as Tibio-talo-calcaneal (TTC) procedures, face challenges with bone resorption leading to loss of compressive stress and prolonged or unsuccessful fusion, which can result in patient pain, recurring surgery, infection, and potential limb amputation.
Innovation Solution
Intramedullary medical devices with a non-linear contracting element made of shape memory alloys that provide sustained compressive forces across the bone fusion site, maintaining pseudo-elastic stress response even with bone resorption, ensuring continuous compression between the tibia, talus, and calcaneus through a pseudo-elastic stress response of the shape memory alloy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional bone fixation devices are used for ankle fusion, then initial compression is achieved, but compressive stress is lost due to bone resorption leading to fusion failure
Solution Approach 1:
The device transitions from a static fixation system to a dynamic one using a shape memory alloy spring that can change its mechanical properties. The spring transitions between martensite (compliant) and austenite (rigid) phases, allowing it to adapt its stiffness and maintain compression dynamically as bone resorption occurs during the fusion process
Solution Approach 2:
The shape memory alloy spring changes its physical parameters (modulus of elasticity, stiffness) in response to temperature changes or stress conditions. This parameter change allows the device to maintain optimal compressive force throughout the fusion process, adapting to the changing mechanical environment as bone resorbs and heals
2Stability of the object's composition
If rigid fixation devices are used to maintain compression, then initial stability is achieved, but the device cannot accommodate bone resorption and movement
Solution Approach 1:
The fixation device incorporates a dynamic element (shape memory alloy spring) that can adjust its mechanical behavior. The spring transitions between compliant and rigid states, allowing the device to accommodate bone resorption and movement while maintaining overall stability of the compression force across the fusion site
Solution Approach 2:
The shape memory alloy spring automatically adjusts to the changing conditions of bone resorption without external intervention. The material's inherent phase transformation properties enable it to self-regulate the compression force, maintaining stability while adapting to the biological processes occurring during fusion
3Adaptability or versatility
If compliant elements are used to accommodate movement, then adaptability to bone resorption is improved, but insufficient compressive force is maintained for successful fusion
Solution Approach 1:
The shape memory alloy spring changes its mechanical parameters (stiffness, modulus) based on temperature or stress conditions. This allows the element to be compliant when needed to accommodate movement and bone resorption, then transition to a rigid state to maintain sufficient compressive force for successful bone fusion
Solution Approach 2:
The shape memory alloy undergoes phase transitions between martensite and austenite phases. During the martensite phase, the material is compliant and can accommodate deformation; during the austenite phase, it becomes rigid and maintains high compressive force, thus resolving the contradiction between compliance and force maintenance
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 intramedullary medical device effectively maintains compressive forces across the ankle joint, enhancing bone fusion success by preventing loss of compressive stress due to bone resorption, thereby reducing the risk of complications and promoting stable, pain-free fusion.
Implementation Method 1
a non-linear contracting element made of shape memory alloys that provide sustained compressive forces across the bone fusion site, maintaining pseudo-elastic stress response even with bone resorption
Implementation Method 2
maintaining pseudo-elastic stress response even with bone resorption, ensuring continuous compression between the tibia, talus, and calcaneus through a pseudo-elastic stress response of the shape memory alloy
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
Intramedullary medical devices (e.g., intramedullary nails) and methods for their use and manufacture are described herein. The intramedullary medical devices described herein may provide sustained compressive forces across a bone fusion site despite bone resorption processes. Through various embodiments, the intramedullary medical devices described herein may provide non-linear force curves relative to displacement. Intramedullary medical devices are described with multiple elements made of different materials. Examples of intramedullary medical devices are described with shape memory alloys.