Reverse Hip Prosthesis Interlocking Cup and Ball Design

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Solution Overview

Problem

Conventional hip implants experience instability and dislocation at extreme ranges of motion due to the nature of the articular femoral ball and acetabular cup design, leading to wear and tear issues.

Innovation Solution

The design is reversed with a femoral cup and an acetabular ball, securely attached via a Morse taper, ensuring the articular surfaces are in full contact, providing increased stability and reduced wear through a concentric interlocking mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a conventional articular femoral ball and acetabular cup design is used, then the hip implant can be easily assembled, but the prosthesis becomes unstable at extreme ranges of motion allowing dislocation

Engineering Contradiction:

Improveease of assemblyVSAvoidstability at extreme range of motion

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent inverts the conventional hip implant design by replacing the articular femoral ball with an articular femoral cup and the acetabular cup with an acetabular ball. This reversal creates an interlocking mechanism where the femoral cup sits within the acetabular cup, and the acetabular ball is contained within the femoral cup, preventing dislocation at extreme ranges of motion while maintaining ease of assembly through the reversed configuration

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If the articular femoral ball is forced into a resilient opening in the acetabular cup, then the assembly is simplified, but the ball may separate from the cup under forces from ambulatory motion

Engineering Contradiction:

Improveassembly simplicityVSAvoidconnection stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

By reversing the design to use an interlocking cup-and-ball configuration where the femoral cup is contained within the acetabular cup and the acetabular ball is contained within the femoral cup, the patent eliminates the need for forcing the ball into a resilient opening. The interlocking geometry provides inherent stability that prevents separation under ambulatory forces while maintaining simple assembly procedures

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If the articular surfaces have limited contact, then the implant design is simpler, but wear increases and weight distribution is poor

Engineering Contradiction:

Improveimplant design complexityVSAvoidwear and weight distribution

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The reversed cup-and-ball configuration creates extensive interlocking contact between the articular surfaces. The femoral cup articulates with the acetabular ball while being contained within the acetabular cup, and the acetabular ball is contained within the femoral cup. This geometry maximizes the contact area between articular surfaces, improving weight distribution and reducing wear without significantly increasing design complexity

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent implements a nested configuration where the femoral cup is nested within the acetabular cup, and the acetabular ball is nested within the femoral cup. This nesting arrangement creates multiple layers of contact and containment, maximizing the articulating surface area and ensuring optimal weight distribution across the joint while minimizing wear through increased surface contact

Inventive Principle:

Principle #7Nested doll (Nesting)

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 configuration enhances the range of motion while minimizing the risk of dislocation and wear, improving weight distribution and reducing the release of wear particles in the joint.

Implementation Method 1

The acetabular ball (8) is solidly and concentrically attached to a central protrusion or stem (9) of the acetabular cup via Morse taper. A femoral cup (6) is preferably solidly attached to a femoral implant by means of a Morse taper.

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS8992627B2Interlocking reverese hip and revision prosthesis and method

Publication Date: 2015.03.31 HIP INNOVATION TECHNOLOGY LLC

AI summary

A reverse hip prosthesis comprising an acetabular cup for implanting in an acetabular socket. The acetabular cup is secured to the acetabular socket. The acetabular cup has a stem extending from the center of a concave portion thereof and an acetabular ball is attached to the stem. A femoral implant has a femoral cup attached to the proximal end thereof. The femoral cup has a stem which can be made with several stem lengths in order to accommodate the various sizing requirements of patients. After implantation of the acetabular cup and ball and the femoral cup, the members are assembled together so that the femoral cup can articulate on the acetabular ball. The prosthesis of the invention has a wide range of motion and substantially improved tribology.