Acetabular Cup Centering Pin Undulating Profile

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Solution Overview

Problem

Existing acetabular prostheses face challenges in accurately positioning the insert within the acetabular cup due to limited self-centering capabilities, material deformation, and risk of chipping or breakage during surgical insertion, especially with fragile materials like ceramics.

Innovation Solution

An acetabular prosthesis featuring a centering unit with a centering pin having an undulating profile along the centering axis, comprising concave and convex parts connected by an inflection, which facilitates stable and accurate insertion and positioning of the acetabular insert within the acetabular cup, even under inclinations, reducing the risk of chipping and improving frictional contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conical coupling is used between the acetabular cup and insert, then stable connection is achieved, but self-centering capability is limited and cross-positioning may occur during surgical insertion

Engineering Contradiction:

Improveconnection stabilityVSAvoidpositioning accuracy

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The centering pin is designed with a spherical head that fits into a corresponding spherical recess in the acetabular cup. This spherical geometry provides multi-directional self-centering capability, allowing the insert to automatically center itself even when significant angular deviations occur during surgical insertion, thereby preventing cross-positioning while maintaining connection stability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Manufacturing precision

If a centering pin with minimal diameter difference is used to reduce positioning errors, then positioning accuracy improves, but the risk of chipping or breakage increases during insertion

Engineering Contradiction:

Improvepositioning accuracyVSAvoidresistance to chipping and breakage

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The spherical head of the centering pin and its corresponding recess provide a curved contact surface that distributes insertion forces evenly, avoiding stress concentration at sharp edges. This curved geometry reduces the risk of chipping or breakage during insertion while maintaining minimal diameter difference for accurate positioning.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The spherical geometry of the centering pin and recess creates a gradual, controlled insertion path that cushions the impact during surgical placement. The curved surfaces allow for progressive engagement rather than sudden contact, protecting the fragile insert material from shock-induced damage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If the centering pin edge contacts the insert surface, then centering guidance is provided, but chipping may occur due to sudden inclination variations

Engineering Contradiction:

Improvecentering guidanceVSAvoidchipping risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The spherical head of the centering pin provides continuous surface contact with the curved recess, distributing mechanical stresses evenly during insertion and throughout articulation. This eliminates stress concentration at sharp edges, preventing chipping even when sudden inclination variations occur during surgical placement or subsequent use.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Ease of operation

If a conical or upturned cone centering pin is used, then centering function is achieved, but frictional resistance during insertion increases

Engineering Contradiction:

Improvecentering functionVSAvoidinsertion force required

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The spherical geometry of the centering pin and recess creates a self-aligning mechanism that reduces frictional resistance during insertion. The curved surfaces allow for smooth, multi-directional movement during centering, requiring less insertion force compared to conical geometries that demand precise alignment and generate higher friction.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 undulating centering pin configuration enhances the stability and accuracy of insert positioning, minimizes the risk of incorrect placement and material damage, and reduces frictional resistance during insertion, thereby ensuring a secure and reliable coupling of the acetabular insert within the acetabular cup.

Implementation Method 1

reduces frictional resistance during insertion, thereby ensuring a secure and reliable coupling

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS10918490B2Acetabular prosthesis

Publication Date: 2021.02.16 LIMACORPORATE SPA

AI summary

Acetabular prosthesis comprising an acetabular cup, an acetabular insert, able to be stably coupled inside the acetabular cup and configured to receive an articulation head and a centering unit configured to guide and center the insertion and stable positioning of the acetabular insert in the acetabular cup. The centering unit comprises a centering hole provided in the acetabular cup and a centering pin provided on the acetabular insert and which develops along a centering axis, configured to be inserted in the centering hole. The centering pin is provided with an external lateral surface that has an undulating development along the centering axis.