Threaded Acetabular Liner Assembly for Secure Shell Alignment

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Solution Overview

Problem

Current methods for aligning and securing the acetabular liner within the acetabular shell in hip replacement surgery are inadequate, leading to a high risk of dislocation and failure due to improper alignment and engagement, particularly with ceramic or metal liners.

Innovation Solution

A prosthetic acetabular liner is designed with a threaded spigot that engages a corresponding threaded apical hole in the acetabular shell, allowing for rotational alignment and a compressive force via a Morse taper to secure the liner in place, using a specialized instrument for precise torque application.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If current alignment methods are used for acetabular liner and shell, then the assembly process is simple, but the risk of dislocation and failure is high due to improper alignment

Engineering Contradiction:

Improverisk of dislocation and failureVSAvoidalignment mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A threaded spigot is introduced as an intermediary alignment feature that engages with a corresponding threaded hole in the acetabular shell. This spigot acts as a mediator between the liner and shell, ensuring precise rotational alignment during assembly while maintaining a relatively simple overall device structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The threaded spigot and hole are pre-configured with matching thread geometries before assembly. This preliminary configuration ensures that when the components are assembled, the threads automatically guide and constrain the rotational alignment, preventing improper positioning before the final securing step.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If rotational alignment method is used with threaded spigot, then proper alignment and engagement is ensured, but the assembly process requires specialized instruments for torque application

Engineering Contradiction:

Improvealignment precisionVSAvoidassembly operation simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The manual alignment process is replaced with a threaded mechanical engagement system. Instead of relying on surgeon skill to align components visually or tactilely, the threaded spigot automatically provides precise rotational alignment through its engagement with the threaded hole, reducing dependency on operator skill.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The alignment mechanism utilizes thread pitch and rotational parameters to achieve precise positioning. By controlling the number of rotations and the thread geometry, the system transforms a complex alignment task into a simple rotational operation with built-in precision.

Inventive Principle:

Principle #35Parameter changes

3Strength

If Morse taper is used to secure liner, then compressive force is applied to secure engagement, but the risk of dislocation remains without additional alignment features

Engineering Contradiction:

Improveengagement strengthVSAvoiddislocation resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention merges two previously separate functions into a unified system: the threaded spigot provides rotational alignment while the Morse taper provides axial compression and secure engagement. This combination ensures both proper orientation and strong mechanical bonding, significantly improving dislocation resistance compared to using either feature alone.

Inventive Principle:

Principle #5Merging (Combining)

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

This design significantly reduces the risk of dislocation and failure by ensuring proper alignment and engagement between the acetabular liner and shell, enhancing the durability and longevity of the hip implant.

Implementation Method 1

a threaded spigot extending outwardly from the apex portion... rotation of the liner in the shell causes the threaded spigot to engage the threaded apical hole and thereby draw the liner into the shell

Methodology Applied

Scientific EffectScrew: Screw

Implementation Method 2

a compressive force via a Morse taper to secure the liner in place

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS20260026946A1Modular Acetabular Cup System

Publication Date: 2026.01.29 RR MEDICAL PTY LTD

AI summary

A prosthetic acetabular liner including a wall that extends from an apex portion to a circumferential rim portion, the wall having: a convex outer surface; a threaded spigot extending outwardly from the apex portion; a concave inner bearing surface; and an opening surrounded by the circumferential rim portion. The liner is rotatably insertable into an acetabular outer shell having a corresponding threaded apical hole, and rotation of the liner in the shell causes the threaded spigot to engage the threaded apical hole and thereby draw the liner into the shell.