Mold-Based Bone Cement Application for Orthopedic Implants
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Solution Overview
Problem
The use of bone cement in orthopedic implants is hindered by the formation of a leathery skin on doughy cement surfaces, which impairs micro-mechanical interlock and adhesive properties, making it difficult to achieve an optimal cement-prosthesis interface, especially when high viscosity cements are not practical for application.
Innovation Solution
A mold body and method for forming a flowable material against a prosthetic implant, which involves a mold cavity conforming to the implant's surface, an inlet port for introducing low viscosity cement, and vents to release air, allowing the cement to adhere and reach a higher viscosity doughy state before implantation, thereby improving micro-mechanical interlock and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low viscosity bone cement is applied directly to the implant, then the cement can flow and adhere to the bone opposing surface, but the cement runs off the implant making application impractical and messy
Solution Approach 1:
A mold is introduced as an intermediary device between the cement and the implant. The mold contains the flowable cement and presses it against the bone opposing surface of the implant, allowing the cement to adhere properly without running off. This mediator enables the use of low viscosity cement while solving the application control problem.
Solution Approach 2:
The cement viscosity is changed over time within the mold. The mold allows the cement to maintain low viscosity during application, then progressively increases viscosity as the cement cures, transforming from a runny state to a doughy state that adheres to the implant surface.
2Ease of operation
If doughy bone cement is used to minimize mess and time, then ease of operation improves, but a leathery skin forms on the surface preventing micro-mechanical interlock
Solution Approach 1:
The mold is used to apply cement to the bone opposing surface before the cement has a chance to form a leathery skin. By pressing the cement against the implant surface while it is still in a tacky state and maintaining contact, the system ensures micro-mechanical interlock occurs before surface deterioration can happen.
Solution Approach 2:
The mold creates a protected environment that prevents air exposure to the cement surface. By keeping the cement contained within the mold and pressed against the implant, the system prevents monomer liquid evaporation that would otherwise cause leathery skin formation.
3Ease of operation
If high viscosity doughy cement is applied, then cement does not run off the implant, but the cement lacks the ability to establish superior micro-mechanical interlock
Solution Approach 1:
The cement viscosity is made dynamic rather than static. The system starts with low viscosity cement that can flow and penetrate the bone opposing surface, then progressively increases to high viscosity as curing occurs. This dynamic viscosity change allows both good application control and superior micro-mechanical interlock.
Solution Approach 2:
The cement application process occurs in distinct stages: first, low viscosity cement is applied while flowable; second, the cement progressively cures and increases in viscosity; third, the cement reaches a doughy state with optimal adhesion. This periodic transformation enables both controlled application and strong bonding.
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 method enhances the quality and strength of the prosthesis-cement interface by ensuring early contact with a tackier cement, preventing air exposure and leathery skin formation, and facilitating easier handling and placement of the implant.
Implementation Method 1
such bone cements can offer an adhesive property to further couple the implant to the host bone
Implementation Method 2
Cement bond strength can be a function of both true adhesion and micro-mechanical interlock that can be established between the cement and the bone opposing surface of the implant
Implementation Method 3
The vent can be configured to permit air to escape therethrough upon the introduction of the flowable material into the void
Data Source
AI summary
An apparatus for forming a flowable material against a prosthetic implant can comprise a mold body having an outer surface and an inner surface. The inner surface can define a mold cavity that is selectively configured to at least partially accept the prosthetic implant in a forming position. An inlet port can be configured on the mold cavity that extends between the inner and outer surfaces. The mold cavity can substantially conform to a profile of a bone opposing surface of the prosthetic implant such that a void is created between the inner surface of the mold body and the bone opposing surface of the prosthetic implant. The inlet port can be configured to permit introduction of the flowable material into the void and against the bone opposing surface of the prosthetic implant.