Ultra-Low Modulus Shape Memory Alloy for Orthopedic Implants
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Solution Overview
Problem
Orthopedic and dental implants made from conventional materials often suffer from stress shielding, leading to bone density reduction and loosening due to their higher elastic modulus compared to bone, necessitating the development of materials with reduced effective modulus and self-adaptive properties to mitigate these issues.
Innovation Solution
A method of fabricating shape-memory alloys comprising titanium, niobium, and zirconium, involving melting, heat treatment, thermo-mechanical processing, and training to achieve an effective modulus of elasticity less than 30 GPa, enabling self-adaptive and corrosion-resistant properties that adjust to the operating environment to reduce stress shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional implant materials (cobalt chrome or titanium) are used, then strength is achieved, but elastic modulus is too high causing stress shielding and bone density reduction
Solution Approach 1:
The patent changes the material parameters by developing shape memory alloys with specific compositions (Ni-Ti, Ti-Nb, Ti-Ni) that exhibit ultra-low effective elastic modulus (less than 30.0 GPa) after training. The training process modifies the material's stress-strain behavior to reduce the effective modulus while maintaining strength, directly addressing the stress shielding problem without sacrificing structural integrity
Solution Approach 2:
The patent introduces dynamic properties to the implant material through shape memory effects. The trained alloy can dynamically adjust its mechanical response to applied stresses, transforming from a static, high-modulus material to a dynamic material that adapts its effective modulus based on loading conditions, thereby reducing stress shielding while maintaining strength
2Stability of the object's composition
If high elastic modulus materials are used, then implant stability is achieved, but bone density reduction and loosening occur
Solution Approach 1:
The patent modifies the mechanical parameters of the implant material to achieve an ultra-low effective elastic modulus (less than 30.0 GPa) through composition control and training processes. This parameter change allows the implant to better match bone stiffness, maintaining stability while preventing the bone density reduction that leads to loosening and improving long-term reliability
Solution Approach 2:
The trained shape memory alloy exhibits self-adaptive behavior where the material automatically adjusts its effective modulus in response to applied stresses. This self-service capability allows the implant to maintain optimal mechanical interaction with bone tissue without external intervention, preventing loosening while ensuring long-term stability and reliability
3Object-affected harmful factors
If modulus reduction is achieved through material composition, then stress shielding is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent achieves modulus reduction through controlled composition changes (adding specific alloying elements like Nb or Ni to Ti) combined with heat treatment and training processes. While the composition is complex, the manufacturing steps follow conventional metallurgical practices, balancing material performance with manufacturing feasibility
Solution Approach 2:
The training process is performed during manufacturing to pre-establish the ultra-low effective modulus properties of the alloy. By completing the modulus reduction and adaptive behavior development during the manufacturing stage rather than during implantation or use, the patent simplifies the overall process while achieving the desired stress shielding reduction
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 resulting alloys exhibit reduced effective modulus, improved biocompatibility, and corrosion resistance, allowing them to adapt to changing bone conditions, thereby reducing bone loss and enhancing implant longevity and safety.
Implementation Method 1
heat treating the alloy formed in (a) by maintaining the alloy at a temperature between 850°C and 1100°C for at least 30 minutes
Implementation Method 2
thermo-mechanically processing the alloy, wherein thermomechanically processing the alloy comprises at least one of hot working, warm working, and cold working, or combinations thereof, and subjecting the alloy to a strain
Implementation Method 3
training the alloy at a constant temperature between 20°C (68°F) and 50°C (122°F) after (c) via a plurality of deformation cycles at a 1-3% strain
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Methods of manufacturing biocompatible, corrosion resistant, self-adaptive, shape-memory titanium-based alloys by using specific ranges of elements in the alloy. Subsequent to melting, the alloy may undergo heat treating, thermo-mechanically processing, and training. Subsequent to training, the alloy has an ultra-low elastic modulus and exhibits self-adaptive, superelastic behavior.