Bone Cement Viscosity Control via Polymer Bead Suspension
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Solution Overview
Problem
Current bone cements used in orthopedic procedures, such as vertebroplasty and kyphoplasty, face challenges with cement leakage due to their liquid phase and rapid hardening, which limits their viscosity and working window, making it difficult to maintain a stable viscosity for effective injection and fracture stabilization.
Innovation Solution
A bone cement formulation that rapidly transitions from separate liquid monomer and powdered polymer components to a high viscosity state with a controlled working window, achieved by using sub-populations of polymer beads with varying molecular weights and sizes, ensuring minimal liquid phase and prolonged stability during injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If liquid phase cement is used for injection, then injection resistance is reduced, but cement leakage occurs outside the vertebra
Solution Approach 1:
The patent changes the viscosity parameter of the bone cement by incorporating polymer beads of specific sizes (0.25mm, 0.5mm, 1mm) and controlling the monomer-to-polymer ratio. This creates a cement that maintains lower viscosity during injection (reducing injection resistance) while achieving higher viscosity after setting (preventing leakage), thus resolving the contradiction between ease of injection and leakage prevention.
2Reliability
If more viscous cement is injected to reduce leakage, then cement leakage is reduced, but the cement hardens very quickly and injection becomes difficult
Solution Approach 1:
The patent creates a dynamic viscosity profile where the cement transitions from a lower viscosity state during injection to a higher viscosity state after setting. The polymer bead suspension allows the cement to be injectable initially, then progressively harden to prevent leakage, making the viscosity property dynamic rather than static throughout the entire process.
Solution Approach 2:
The patent performs preliminary action by suspending polymer beads in the cement mixture before injection. This pre-prepared suspension ensures that the cement has the optimal viscosity for injection at the moment of delivery, while the subsequent hardening process automatically provides leakage prevention without requiring additional intervention.
3Reliability
If cement is injected during doughing time and beginning of polymerization to reduce leakage, then cement leakage is reduced, but the working window becomes too short for effective injection
Solution Approach 1:
The patent carefully controls the polymerization parameters by selecting specific polymer bead sizes and concentrations. This optimization creates a working window that is extended enough to allow complete injection procedures while ensuring that leakage prevention is achieved once the cement sets, resolving the time-related contradiction.
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 cement achieves a high viscosity within minutes of mixing, maintaining stability for several minutes, reducing leakage and allowing for effective injection and fracture stabilization, thereby enhancing the success of orthopedic procedures like vertebroplasty and kyphoplasty.
Implementation Method 1
Polymerization begins by the 'addition mechanism' in which a monomer becomes unstable by reacting with an initiator, a volatile molecule that is most commonly a radical
Implementation Method 2
Radicals are formed when heat or light cleaves the peroxide molecule
Implementation Method 3
peroxide is typically cleaved by adding a chemical activator such as N, N-dimethyl-p-toluidine
Data Source
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AI summary
A bone cement comprising an acrylic polymer mixture. The cement is characterized in that it achieves a viscosity of at least 500 Pascal-second within 180 seconds following initiation of mixing of a monomer component and a polymer component and characterized by sufficient biocompatibility to permit in-vivo use.