Porous Hip Stem Polymer Bonding and Tactile Alignment
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Solution Overview
Problem
Current prosthetic hip stems face challenges in achieving optimal articulating movement and alignment during minimally invasive procedures due to limited visualization, and existing bonding methods can compromise the fatigue strength of the core material.
Innovation Solution
A prosthetic hip stem design featuring a core with a polymer matrix layer and a porous metal layer, where the polymer matrix connects the core and porous metal layer, and includes a contoured neck portion with a version indicator element for tactile alignment and enhanced mechanical interconnection features, eliminating the need for sintering to maintain core fatigue strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous surface layer is sintered to the core by heating to high temperature, then the connection between core and porous surface layer is enhanced, but the fatigue strength of the core material is compromised
Solution Approach 1:
A polymer coating layer is applied as an intermediary between the metal core and the porous surface layer. This polymer layer serves as a bonding medium that connects the two layers without requiring high-temperature sintering that would compromise the core's fatigue strength. The polymer coating is applied at lower temperatures and provides adequate mechanical interconnection.
2Adaptability or versatility
If the neck portion has a standard profile, then structural strength is maintained, but the degree of articulating movement is limited
Solution Approach 1:
The neck portion features a contoured profile with varying cross-sectional dimensions optimized for different regions. The upper neck has a smaller diameter to maximize articulating movement, while the lower neck maintains sufficient diameter for structural strength. This localized variation in geometry allows the design to simultaneously achieve both mobility and strength requirements.
3Manufacturing precision
If direct visualization of the hip stem is used during implantation, then precise positioning is achieved, but the procedure cannot be minimally invasive
Solution Approach 1:
Version indicator elements (such as bumps or protrusions) are integrated directly onto the hip stem's neck portion. These tactile features allow the surgeon to sense the stem's orientation and version through touch alone during implantation, enabling precise positioning without direct visualization. This self-indicating feature makes minimally invasive procedures feasible while maintaining positioning accuracy.
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 design allows for increased articulating movement and precise alignment during minimally invasive procedures while maintaining the core's fatigue strength, facilitating better implantation and integration with surrounding bone tissue.
Implementation Method 1
a polymer matrix layer substantially covering the stem portion of the core... The polymer matrix layer connects the core and the porous metal layer
Data Source
AI summary
A prosthetic hip stem for use in a prosthetic hip joint. The hip stem generally includes a core having a stem portion and a neck portion, a polymer matrix layer substantially covering the stem portion of the core, and a porous metal layer substantially covering the polymer matrix layer. The polymer matrix layer connects the core and the porous metal layer, and may be injection molded therebetween. The neck portion of the hip stem has a relatively thin or slender profile which allows for an increased degree of articulating movement of the hip stem with respect to the acetabular component of a prosthetic hip joint. The neck portion of the hip stem additionally includes a version indicator element, such as a bump or a protrusion, which may be tactilely felt by a surgeon to aid the surgeon in positioning the hip stem during a minimally invasive total hip arthroplasty procedure, for example, where direct visualization of the hip stem by the surgeon may not be possible. Additionally, the core of the hip stem includes grooves, ridges, flats, dimples or other features to enhance the mechanical interconnection between the core and the polymer matrix layer.