Bone Cement Viscosity Control for Leakage Prevention
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Solution Overview
Problem
Current bone cements used in procedures like vertebroplasty and kyphoplasty often leak due to their liquid phase during injection, and existing viscous materials harden quickly, making them difficult to inject effectively, while also potentially emitting heat and toxic substances during polymerization.
Innovation Solution
A bone cement formulation that rapidly transitions from a liquid monomer and powdered polymer mixture to a high viscosity state with minimal liquid phase, maintaining this viscosity for a working window of several minutes, achieved by using sub-populations of polymer beads with varying molecular weights and sizes to control polymerization kinetics and viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bone cement is injected in liquid phase to reduce injection resistance, then ease of injection is improved, but cement leakage outside vertebra increases
Solution Approach 1:
The patent applies parameter changes by controlling the viscosity of bone cement within a specific range (50-500 Pascal-second) to simultaneously achieve ease of injection and prevent leakage. The viscosity is adjusted through polymer molecular weight selection and monomer-to-polymer ratio optimization, allowing the cement to flow adequately during injection while maintaining sufficient body to remain contained within the vertebra.
Solution Approach 2:
The patent utilizes phase transitions by designing bone cement that transitions from liquid monomer and powder polymer components to a gel-like state during injection. This phase change occurs through polymerization reactions initiated by mixing, transforming the material from a free-flowing liquid to a semi-solid gel that resists leakage while maintaining injectability during the transition period.
2Reliability
If viscous material is used to reduce cement leakage, then cement leakage control is improved, but injection difficulty increases
Solution Approach 1:
The patent resolves this contradiction by precisely controlling viscosity parameters within the 50-500 Pascal-second range. This parameter optimization ensures the cement is viscous enough to prevent leakage but not so viscous that it becomes difficult to inject, achieving a balance between containment and deliverability through systematic adjustment of formulation variables.
3Duration of action of moving object
If polymerization reaction proceeds rapidly to achieve high viscosity, then working time control is improved, but heat generation and toxic substance emission increase
Solution Approach 1:
The patent controls the polymerization reaction rate by adjusting parameters such as initiator concentration, monomer-to-polymer ratio, and polymer molecular weight. These parameter changes allow the working time to be extended while preventing excessive heat generation and toxic substance emission by slowing the polymerization kinetics to a manageable rate that completes the setting process without dangerous byproduct accumulation.
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 allows for effective injection and stabilization of fractures with reduced leakage, maintaining high viscosity during procedures, thus facilitating vertebral repair and restoration of vertebral height without significant hardening or toxicity issues.
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
A broad aspect of the invention relates to a bone cement characterized by a rapid transition from separate liquid monomer and powdered polymer components to a single phase characterized by a high viscosity
Data Source
AI summary
A bone cement comprising an acrylic polymer mixture which is formulated to have a relatively high viscosity for a relatively long window, due to distributions of molecular weights and/or sizes of acrylic beads.