Offset Anti-Rotational Element for Prosthetic Component Stability
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Solution Overview
Problem
Prosthetic components in Total Hip Replacement (THR) procedures face challenges such as high frictional torque leading to rotational movements, wear, and corrosion, particularly with metal and polyethylene bearings, and the need for multiple sizes of femoral heads and sleeves, which increases manufacturing costs and storage requirements.
Innovation Solution
Incorporating an anti-rotational element with a parallel and offset axis of rotation in prosthetic components to resist rotational movement, allowing for multiple engagement positions and adjusting relative heights, and using asymmetrical designs with planar or recessed surfaces to enhance stability and reduce the risk of mal-rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ridges and grooves are machined into the conical element to reduce bursting stresses, then the risk of ceramic head cracking is minimized, but cavities appear where fluid can nest leading to crevice corrosion that weakens the frictional fit
Solution Approach 1:
The patent converts the harmful effect of fluid nesting in cavities by redesigning the stress distribution mechanism. Instead of using ridges and grooves that create fluid-trapping cavities, the invention uses a conical element with optimized geometry that distributes stresses without creating enclosed spaces, thereby eliminating crevice corrosion while maintaining protection against ceramic head cracking
Solution Approach 2:
The patent applies local quality by modifying specific regions of the conical element's surface geometry. The conical element features localized geometric variations that provide stress distribution exactly where needed, while maintaining smooth continuous surfaces that prevent fluid accumulation in other critical areas
2Adaptability or versatility
If multiple sizes of femoral heads and sleeves are provided to suit different patients, then the adaptability to different patient requirements is improved, but the manufacturing cost and storage requirements increase
Solution Approach 1:
The patent implements universality by designing the conical element with adjustable positioning capabilities. A single conical element design can be positioned at multiple angles and locations within the femoral head recess, allowing one component to serve multiple functions that previously required multiple different sized components. This reduces the number of unique parts needed while maintaining the ability to accommodate different patient anatomies
Solution Approach 2:
The patent applies dynamics by enabling the conical element to be positioned at variable locations and orientations within the femoral head recess. This dynamic positioning capability allows the same conical element to adapt to different patient requirements through adjustable placement rather than requiring multiple fixed-size components
3Stress or pressure
If circular ridges and grooves are provided on the taper junction to even out stresses, then stress distribution is improved, but the frictional fit at the component interface is reduced
Solution Approach 1:
The patent applies asymmetry by replacing the traditional symmetric circular ridges and grooves with an asymmetric conical geometry. The conical element features a tapered surface with specific angular and radial variations that provide stress distribution while maintaining continuous contact. This asymmetric design eliminates the gaps created by circular features, preserving the frictional fit necessary for secure component attachment
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 anti-rotational element provides rotational stability, minimizes wear and corrosion, and allows for adjustable positions of prosthetic components, reducing the need for multiple sizes and enhancing surgical flexibility without compromising compatibility with standard replacement components.
Implementation Method 1
The sleeves are usually configured for a tight frictional fit onto the conical element... the anti-rotational element configured to resist rotational movement between the inter-engaging parts
Data Source
AI summary
The invention relates to a prosthesis comprising a first component (10) and a second component (60), wherein the first and second components have respective inter-engaging parts (24,64) and wherein at least one of the first or second components comprises an anti-rotational element (32,66) configured to resist rotational movement between the inter-engaging parts and wherein the inter-engaging parts share an axis of rotation such that they are engageable in a plurality of relatively rotated positions and wherein the axis of rotation of the inter-engaging part of one of the first or second components is parallel to but offset from a central axis of said first or second component.