Shape Memory Polymer Bone Fixation Device
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Solution Overview
Problem
Current internal fixation devices, such as those made of metal, fail to maintain adequate fixation and compression across bone fractures over time, leading to increased risk of interfragmentary motion and non-union or pseudo-arthrosis due to resorption of necrotic surfaces and loss of compression.
Innovation Solution
An internal fixation device featuring a shape memory polymer material with features such as protrusions or particulate materials, including ceramic, that expands radially and shortens axially to securely fixate the device to the bone, ensuring symmetrical or asymmetrical expansion and maintaining compression at the fracture site.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal fixation devices (stainless steel or titanium) are used for bone fracture fixation, then initial fixation strength is achieved, but fixation stability and compression maintenance deteriorate over time due to resorption of necrotic surfaces
Solution Approach 1:
The patent applies parameter changes by utilizing the phase transition temperature of shape memory polymer material. The device is inserted in a deformed state at temperatures below the phase transition point, then heated to above the phase transition temperature to trigger radial expansion and axial shortening, thereby changing the physical parameters of the material to achieve stable fixation and maintain compression over time
Solution Approach 2:
The patent employs composite materials by combining shape memory polymer material with metallic components (such as stainless steel or titanium rods). This composite structure integrates the initial strength advantage of metals with the time-dependent stability and compression maintenance capabilities of shape memory polymers, resolving the contradiction between initial fixation strength and long-term reliability
2Reliability
If shape memory polymer material is used for internal fixation, then fixation stability and compression maintenance are improved over time, but device complexity increases due to temperature control requirements
Solution Approach 1:
The patent applies self-service by utilizing the body's natural temperature (approximately 37°C) as the heat source to trigger the phase transition of the shape memory polymer material after implantation. This eliminates the need for external heating devices or complex temperature control systems, reducing device complexity while maintaining the reliability benefits of shape memory effects
Solution Approach 2:
The patent leverages phase transitions of the shape memory polymer material at a specific phase transition temperature. The material transitions from a flexible state at lower temperatures to an expanded rigid state at body temperature, enabling automatic activation of the fixation mechanism without requiring complex external control systems
3Ease of manufacture
If uniform expansion of shape memory material is assumed, then device design is simplified, but actual fixation performance deteriorates due to asymmetric expansion and shifting
Solution Approach 1:
The patent applies asymmetry by designing the shape memory polymer material with non-uniform cross-sectional geometry or asymmetric internal structures. This intentional asymmetry compensates for the natural tendency of the material to expand asymmetrically during phase transition, ensuring that the final expanded configuration achieves symmetric and accurate fixation positioning despite the complex expansion behavior
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 device provides stable fixation and compression across the fracture site, reducing the risk of non-union or pseudo-arthrosis by maintaining adequate expansion and load-bearing capacity over the healing period, while also allowing for gradual resorption and dynamization.
Implementation Method 1
the polymer material includes shape memory qualities
Implementation Method 2
When it is heated to a deformation temperature (i.e., the deformation temperature (Tf) as will be described hereinafter), it can be recovered to the memorized shape
Implementation Method 3
this shape-memory material is reheated by, for example, bringing into contact with hot water (sterilized saline) at the deformation temperature (Tf) or above
Implementation Method 4
the shape-memory material for bone fixation is recovered to the original molded article in the shape of a thick and round bar and comes in contact closely to the endosteal surface and/or cancellous bone
Data Source
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AI summary
The present disclosure relates to an internal fixation device including an interface portion, a polymer material coupled to the interface portion, wherein the polymer material includes at least one feature on a surface of the polymer material, and means for allowing adequate expansion of the polymer material on each side of the bone fracture site. A method of fixating the internal fixation device to a bone and other internal fixation devices and methods for fixating are also disclosed.