Porous Bone Insert Offset Structure for Sclerotic Bone Fixation
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Solution Overview
Problem
Existing bone implant devices fail to securely attach to bones with less porous or sclerotic structures, leading to instability and increased risk of failure due to mismatched modulus of elasticity and stress shielding, resulting in cement breakdown and loosening.
Innovation Solution
A bone insert with a porous cap and stem structure, featuring micro struts and fenestrations, designed to match the modulus of elasticity of the host bone, promoting bone ingrowth and interdigitation with cement, thereby enhancing stability and resistance to fatigue failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid metal bone augment spacer device is used to adjust position, then the implant can be securely attached to the bone, but the device does not have bone ingrowth surfaces and cannot stabilize the cement mantle
Solution Approach 1:
The bone insert is constructed with a porous structure featuring interconnected pores and struts throughout the body. This porous configuration provides bone ingrowth surfaces that allow cement to interdigitate and penetrate into the bone insert, creating mechanical interlocking. The porous structure simultaneously maintains structural integrity for position adjustment while enabling cement mantle stabilization through interdigitation, resolving the contradiction between secure attachment and cement stability.
2Ease of manufacture
If PMMA cementing is used to secure the bone implant, then the implant can be attached to the bone, but the cement does not interdigitate or penetrate the bone in sclerotic bone, leading to insufficient fixation strength
Solution Approach 1:
The porous structure of the bone insert provides numerous interdigitating surfaces that extend into the cement mantle. The interconnected pores create mechanical interlocking with the PMMA cement, allowing the cement to penetrate and interdigitate with the bone insert even in sclerotic bone conditions. This porous configuration significantly enhances fixation strength by creating multiple bonding interfaces between the cement and bone insert, overcoming the limitations of conventional cementing in dense bone.
Solution Approach 2:
The bone insert creates a composite construct combining the porous metal insert with the PMMA cement mantle. This composite structure leverages the interdigitation between the porous insert and cement to achieve superior fixation strength. The composite material approach allows the cement to mechanically interlock with the porous structure, creating a synergistic effect that provides enhanced fixation compared to either component alone, particularly in sclerotic bone where conventional cementing fails.
3Manufacturing precision
If a solid metal screw device is used to adjust offset, then the implant position can be controlled, but the device does not interdigitate with cement and is prone to pullout failure under cyclic loading
Solution Approach 1:
The porous structure with interconnected struts and pores provides extensive interdigitation surfaces that mechanically lock with the cement mantle. This porous configuration creates multiple bonding interfaces that distribute cyclic loading forces throughout the insert-cement-bone assembly, preventing pullout failure. The porous structure maintains precise position control capability while simultaneously providing superior resistance to cyclic loading and pullout forces compared to solid metal devices.
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 improves cement fixation, reduces stress shielding, and minimizes movement between the implant and bone, extending the life of the implant by preventing cement breakdown and loosening.
Implementation Method 1
the bone insert also interdigitates with the cement in securing the bone insert to the cement, while the interdigitation with the cement produces a composite construct that resists breakdown at the cement insert interface with cyclic loading
Implementation Method 2
designed to match the modulus of elasticity of the host bone, promoting bone ingrowth and interdigitation with cement
Implementation Method 3
leading to instability and increased risk of failure due to mismatched modulus of elasticity and stress shielding
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.