Bone Cement Mesh Reinforcement Fatigue and Thermal Management
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Solution Overview
Problem
Current bone cements like PMMA and structural biomaterials such as calcium phosphate and hydroxyapatite suffer from low fatigue resistance and mechanical properties, leading to thermal necrosis, stress shielding, and premature failure in orthopedic applications due to their brittleness and susceptibility to stress crazing.
Innovation Solution
A mesh device impregnated with bone cement or biomaterials, featuring a shape memory alloy like Nitinol, is used to enhance fatigue life by distributing stress and absorbing heat from exothermic polymerization reactions, similar to rebar in cement, and providing reinforcement through porous fabric meshes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PMMA bone cement is used to anchor artificial joints, then primary stability and fast remobilization are achieved, but thermal necrosis occurs due to highly exothermic polymerization reaction heating the cement to 82.5°C
Solution Approach 1:
A mesh device made of heat-absorbing or heat-conducting material is introduced as an intermediary between the bone cement and the surrounding tissue. The mesh absorbs or conducts away the heat generated during polymerization, protecting the bone from thermal necrosis while allowing the cement to maintain its strength and stability functions.
Solution Approach 2:
The patent modifies the thermal parameters of the bone cement system by incorporating a mesh structure that changes the heat distribution pattern. The mesh alters the temperature profile during polymerization, reducing peak temperatures at the bone-cement interface while maintaining the exothermic reaction necessary for cement setting and strength development.
2Strength
If PMMA bone cement is used to fill spaces between prosthesis and bone, then high compression strength and creep resistance are achieved, but stress shielding occurs due to lower Young's modulus (1.8-3.1 GPa) causing stresses to load into the cement instead of bone
Solution Approach 1:
The patent creates a composite structure combining the bone cement with a mesh device made of material having different mechanical properties. This composite construction allows the cement to provide compression strength while the mesh structure helps distribute and transfer stresses more effectively to the bone, reducing stress shielding effects.
Solution Approach 2:
The mesh device segments the stress distribution within the bone cement, creating multiple load paths through its interconnected structure. This segmentation prevents stress concentration in single locations and facilitates more uniform stress transfer to the surrounding bone, mitigating stress shielding.
3Stability of the object's composition
If PMMA bone cement is used as a grouting agent, then it prevents motion between prosthesis and bone, but brittleness and susceptibility to stress crazing lead to crack formation and eventual failure
Solution Approach 1:
The patent forms a composite material system where the mesh device is embedded within or adjacent to the bone cement. This composite structure combines the motion-preventing properties of the cement with the crack-resistance and ductility of the mesh material, creating a more reliable assembly resistant to fatigue and stress crazing.
Solution Approach 2:
The mesh device acts as a pre-positioned reinforcement that cushions and distributes stresses before they can initiate or propagate cracks in the brittle bone cement. The mesh provides a safety network that prevents stress concentration and crack formation during loading cycles.
4Stability of the object's composition
If hydroxyapatite, calcium phosphate, or tricalcium phosphate are used as fillers to replace bone, then bone remodeling and healing are promoted, but low crack resistance and fatigue durability prevent load-bearing application
Solution Approach 1:
The patent creates a composite structure where the bioactive materials (hydroxyapatite, calcium phosphate, or tricalcium phosphate) are combined with a reinforcing mesh device. This composite construction provides the bone remodeling properties of the bioactive materials while the mesh structure supplies the necessary crack resistance and fatigue durability for load-bearing applications.
Solution Approach 2:
The mesh device segments and reinforces the brittle bioactive material structure, creating multiple load-bearing pathways that prevent crack propagation. This segmentation allows the bioactive material to maintain its bone remodeling functionality while gaining the mechanical strength needed for load-bearing use.
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 mesh structure significantly improves the fatigue and mechanical properties of bone cements and biomaterials, reducing the risk of thermal necrosis, enhancing load distribution, and increasing the durability of implants by acting as a rebar-like reinforcement and heat absorber.
Implementation Method 1
absorbing heat from exothermic polymerization reactions
Implementation Method 2
distributing stress and absorbing heat
Implementation Method 3
The mesh structure includes a shape memory alloy
Implementation Method 4
The porous fabric mesh is manufactured from superelastic Nitinol wire
Data Source
AI summary
A device includes a bone cement or a biomaterial and a mesh structure impregnated with the bone cement or the biomaterial. The mesh structure reinforces the bone cement or the biomaterial and reinforces the material's fatigue properties. The mesh structure may be made of a shape memory alloy.