Flexible Snap-Fit Prosthetic Component for Joint Replacement

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Solution Overview

Problem

Current joint replacement surgeries using stiff metal prosthetics face issues such as metal erosion, metallosis, osteolysis, and stress shielding, leading to bone resorption and complications like aseptic loosening of bone cement.

Innovation Solution

Development of flexible prosthetic components with snap-fit technology using biocompatible polymers that interlock with resected bone via protrusions and recesses, eliminating the need for bone cement and allowing natural stress distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If stiff metal prosthetics are used for joint replacement, then structural strength and load-bearing capacity are improved, but stress shielding occurs leading to bone resorption and osteolysis

Engineering Contradiction:

Improvestructural strengthVSAvoidstress shielding

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The prosthetic component uses a composite structure combining metal elements with bone cement (polymethylmethacrylate). The metal provides structural strength and load-bearing capacity, while the bone cement fills the interface between metal and bone, allowing stress distribution and reducing stress shielding effects on the bone.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The prosthetic design incorporates localized features including protrusions on the metal component that interface with recesses in the bone cement, creating localized stress distribution zones. The bone cement itself has different mechanical properties than the metal, providing a gradient of stiffness that reduces overall stress shielding while maintaining necessary structural strength.

Inventive Principle:

Principle #3Local quality

2Strength

If stiff metal prosthetics are used for joint replacement, then load-bearing capacity is improved, but metal erosion and metallosis occur leading to osteolysis

Engineering Contradiction:

Improveload-bearing capacityVSAvoidmetal erosion

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The prosthetic system uses a composite approach combining metal with bone cement and polyethylene components. The metal provides load-bearing capacity while the bone cement and polyethylene act as protective interfaces, reducing direct metal-on-metal or metal-on-bone contact that causes erosion and metallosis.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The bone cement and polyethylene components serve as intermediary materials between the metal prosthetic and the bone/tissue. These intermediaries prevent direct contact between metal and biological tissue, eliminating the harmful effects of metal erosion and metallosis while still allowing effective load transfer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If bone cement is used to secure metal prosthetics to bone, then fixation strength is improved, but aseptic loosening occurs over time

Engineering Contradiction:

Improvefixation strengthVSAvoidbond stability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The fixation system is segmented into multiple components: the metal prosthetic with protrusions, the bone cement matrix, and the polyethylene insert. This segmentation allows each component to perform its specific function - the protrusions provide mechanical interlocking, the bone cement provides chemical and mechanical bonding, and the polyethylene provides a stable articulating surface - reducing the risk of overall loosening.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fixation system uses composite materials including polymethylmethacrylate bone cement combined with metal and polyethylene. This composite approach provides both immediate fixation strength through the cement's rapid setting and long-term reliability through the combined mechanical and biological properties of the material system.

Inventive Principle:

Principle #40Composite materials

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 flexible prosthetic components provide secure mechanical retention, reduce bone resorption, and minimize complications associated with metal prosthetics, enhancing the stability and longevity of joint replacements.

Implementation Method 1

The elasticity of the flexible prosthetic components in conjunction with fabricated protrusions will enable these prosthetic components to be slipped over and snap-fit around resected bone

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10952859B2Flexible snap-fit prosthetic component

Publication Date: 2021.03.23 HOWMEDICA OSTEONICS CORP

AI summary

Disclosed herein are flexible prosthetic components that are designed to be snap-fit to bone of a patient. The prosthetic components each have an outer articular surface and an inner bone contacting surface opposing the outer articular surface. The bone contacting surface has an anterior surface and an opposing posterior surface configured to contact corresponding anterior and posterior surfaces of the patient's bone. At least one of the anterior and posterior surfaces includes one or more protrusions extending outwardly therefrom. The anterior and posterior surfaces of the prosthetic components may flex toward and away from one another such that the one or more protrusions may snap-fit into corresponding recesses in the bone. The bone of the patient may be resected to include planar surfaces or resurfaced to include a curved surface corresponding to the respective bone contacting surface of the prosthetic components.