Porous Bone Insert Structure for PMMA Cement Interdigitation
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Solution Overview
Problem
Existing bone implant devices fail to securely attach to sclerotic bones due to insufficient interdigitation of PMMA cement, leading to potential loosening and failure under repetitive forces, especially in joints like the knee.
Innovation Solution
A bone insert with a porous cap and stem structure, featuring micro struts and a barrier, designed to interdigitate with cement and match the modulus of elasticity of the host bone, promoting bone ingrowth and minimizing contact area to reduce friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PMMA cementing is used to attach bone implant to bone, then the implant can be secured to the bone surface, but the cement fails to interdigitate with sclerotic bone sufficiently, leading to loosening and failure under repetitive forces
Solution Approach 1:
The bone insert is constructed with a porous structure featuring numerous interconnecting pores and channels throughout the insert body. This porous configuration enables the PMMA cement to penetrate and interdigitate with the insert, creating mechanical interlocking that significantly enhances cement-bone bonding strength and prevents loosening under repetitive forces.
Solution Approach 2:
The invention creates a composite construct comprising the bone insert, PMMA cement, and host bone. The porous insert structure serves as a scaffold that combines with the cement and bone to form a unified composite material system, improving overall bonding strength and resistance to repetitive forces through synergistic properties of all components.
2Ease of operation
If a solid metal bone augment spacer device is used to adjust position, then the implant position can be controlled, but the device does not provide bone ingrowth surfaces and cannot stabilize the cement mantle
Solution Approach 1:
The bone insert replaces solid metal spacers with a porous structure that provides both position adjustment capability and bone ingrowth surfaces. The porous configuration allows cement penetration and creates mechanical interlocking, thereby stabilizing the cement mantle while maintaining the ability to control implant position.
Solution Approach 2:
The bone insert serves multiple functions simultaneously: it acts as a position adjustment mechanism, provides bone ingrowth surfaces for stabilization, creates mechanical interlocking with cement, and serves as a structural scaffold. This multi-functionality eliminates the need for separate devices for each purpose.
3Strength
If the bone insert has a porous structure to interdigitate with cement, then bonding strength is improved, but the contact area between insert and implant is reduced, potentially increasing friction and wear
Solution Approach 1:
The bone insert features localized quality variations: the porous structure is concentrated in regions requiring cement interdigitation and bonding, while specific contact interfaces maintain appropriate surface characteristics to minimize friction and wear. This localized differentiation allows simultaneous optimization of bonding strength and reduction of harmful frictional effects.
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 bone insert enhances the stability of the cement-bone interface, resisting crack propagation and pullout, while matching the mechanical properties of the bone to extend the implant's lifespan and improve joint function.
Implementation Method 1
The bone insert can include a cap and an elongated stem that can be highly porous structures... The PMMA can then cure to secure bone implant device to the bone
Implementation Method 2
The bone insert enhances the stability of the cement-bone interface, resisting crack propagation and pullout
Implementation Method 3
The barrier structure of the bone insert can be placed against the surfaces of the host bone surrounding the hole
Implementation Method 4
The cap of the bone insert can be a curved convex surface... The small focal point contact surface area between the bone insert and the bone implant is important because it minimizes the contact area between these metal components. Movement between the bone insert and the bone implant results in friction and wear of these components
Implementation Method 5
The bone insert with a porous cap and stem structure, featuring micro struts and a barrier, designed to interdigitate with cement and match the modulus of elasticity of the host bone, promoting bone ingrowth
Data Source
AI summary
A bone insert includes a cap having a convex top surface, an elongated stem, and a barrier between the cap and the stem. The stem of the bone insert is inserted into a hole formed in a host bone until the barrier is pressed against the exposed bone. The bone implant can be placed against a small focus contact point on the cap. Liquid cement can be injected into a space volume between the host bone and a bone implant. The cap can be made of a material and/or have surface features that create a strong bond with the cement when the liquid cement cures. The stem can be made of a material and/or have bone ingrowth surface features that create a strong bond with the bone.