Prosthetic Stem Case for Uniform Cement Fixation and Bone Protection

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Solution Overview

Problem

Existing prosthetic components, such as tibial, femoral, and humeral components, face issues like bone resorption due to direct metal contact, loss of fixation, and instability due to non-uniform cementation, leading to frequent replacements.

Innovation Solution

A biocompatible case-like device is used to cover the prosthetic components, ensuring a stable and uniform layer of bone cement adhesion, preventing direct metal-bone contact and maintaining a consistent distance, thereby stabilizing the implant.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a metal prosthetic stem is directly implanted into bone, then the prosthesis provides structural support, but bone resorption occurs due to direct metal-bone contact

Engineering Contradiction:

Improvestructural supportVSAvoidbone resorption

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a case-like device made of biocompatible material as an intermediary between the metal prosthetic stem and the bone. This intermediate layer prevents direct metal-bone contact that causes bone resorption, while still allowing the prosthesis to provide structural support. The case-like device acts as a mediator that transmits loads without causing the harmful stress shielding effect.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite material construction by combining the metal prosthetic stem with a biocompatible material case-like device. This composite structure allows the metal component to provide strength and rigidity while the biocompatible material layer prevents bone resorption, creating a system that leverages the advantages of both materials.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If bone cement is used to fix the prosthesis, then the implant achieves initial stability, but non-uniform cementation causes loss of fixation

Engineering Contradiction:

Improveinitial stabilityVSAvoidfixation stability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The case-like device is pre-formed with a uniform geometry before implantation. This preliminary preparation ensures that when bone cement is applied, it distributes evenly around the prosthetic stem within the case-like device, preventing the non-uniform cementation that leads to fixation failure. The pre-formed structure guides uniform cement distribution.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The case-like device provides a uniform, homogeneous structure that ensures even distribution of bone cement around the prosthetic stem. This homogeneity in the cement layer thickness and distribution prevents weak points in the fixation, thereby improving the reliability and long-term stability of the implant.

Inventive Principle:

Principle #33Homogeneity

3Productivity

If the prosthetic stem is positioned blindly in the diaphysis, then implantation is quick, but the stem tip contacts bone causing resorption

Engineering Contradiction:

Improveimplantation speedVSAvoidbone resorption

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The case-like device serves as a pre-prepared protective cushion that is implanted first. This beforehand protection ensures that even if the prosthetic stem is positioned quickly without precise visualization, the stem tip cannot contact the bone directly because the case-like device is already in place as a protective barrier, preventing bone resorption.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Object-affected harmful factors

If centering rings are added to the stem, then some contact is prevented, but the solution is not entirely effective

Engineering Contradiction:

Improvemetal-bone contactVSAvoidstem structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent separates the prosthetic system into distinct functional components: the metal prosthetic stem for structural support, the case-like device for protection and cement containment, and the bone cement for fixation. This segmentation allows each component to perform its specific function effectively, with the case-like device providing complete protection against bone contact without modifying the stem structure.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20260047935A1Case-like device and prosthetic component equipped with such device

Publication Date: 2026.02.19 TECRES SPA

AI summary

Prosthetic component provided with a stem, adapted to be implanted in use at a bone of a patient, such as for example a tibial and/or femoral component of a knee prosthesis or a femoral component of a hip prosthesis or a humeral component of a shoulder prosthesis, or a component of an elbow prosthesis, including a device adapted to externally cover and/or to house at its interior at least the stem of the prosthetic component, wherein the device is in use placed between the prosthetic component and the bone of the patient, suitable to stably constrain in use the prosthetic component to the bone of the patient and to prevent the direct contact between prosthetic component and bone of the patient.