Antibiotic-Coated Knee Spacer with Locking Segments

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Solution Overview

Problem

Conventional static spacers for infected prosthetic knee joints lack sufficient stability, making them difficult to install and remove, and may contaminate the medullary cavity, while also providing inadequate antibiotic treatment and limited adjustability.

Innovation Solution

A temporary knee replacement system comprising tibial and femoral rods with antibiotic coatings, C-shaped channels, and a locking spacer that allows for adjustable spacing and easy removal, along with a kit providing various sizes and lengths to accommodate different patients and procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If conventional static spacers are used, then the joint is supported, but the stability is insufficient and the device is difficult to install and remove

Engineering Contradiction:

Improvejoint stabilityVSAvoidinstallation and removal ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The spacer is divided into multiple segments that can be independently inserted into the medullary cavity through separate incisions. Each segment contains locking mechanisms that can be engaged or disengaged independently, allowing for easy assembly during installation and systematic disassembly during removal, thereby improving both stability and operational ease

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spacer incorporates dynamic locking mechanisms that can be adjusted between locked and unlocked states. The locking elements feature cam-actuated mechanisms that provide mechanical advantage during installation, allowing secure engagement with minimal force, and can be easily released during removal, resolving the contradiction between stability and ease of operation

Inventive Principle:

Principle #15Dynamics

2Stability of the object's composition

If intra-medullary rod is installed to support the joint, then joint stability is improved, but the procedure contaminates the medullary cavity and makes removal difficult

Engineering Contradiction:

Improvejoint stabilityVSAvoidmedullary cavity contamination

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The spacer is segmented into multiple sections that can be inserted through separate small incisions rather than requiring extensive medullary cavity exposure. This segmentation minimizes the surgical footprint and reduces contamination risk while maintaining structural integrity and joint stability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spacer is designed as a temporary implant intended for removal after a specific healing period. The materials selected allow for easy removal without causing additional contamination or damage to the medullary cavity, embodying the principle of using temporary, easily removable components for short-term support

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If conventional spacers are used, then antibiotic treatment is provided, but the treatment depth is limited and adjustability is restricted

Engineering Contradiction:

Improveantibiotic treatment effectivenessVSAvoidspacing adjustability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The spacer is divided into multiple segments that can be independently adjusted in length and position. Each segment can be customized to achieve the desired total spacing, allowing precise adaptation to different patient anatomies and infection scenarios while maintaining effective antibiotic distribution throughout the entire spacer structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spacer segments are designed with universal interfaces and standardized dimensions that allow for various combinations to achieve different total lengths and configurations. This modularity provides both deep antibiotic treatment coverage and customizable spacing adjustment, resolving the contradiction between treatment reliability and adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 system provides improved joint stability, effective antibiotic treatment deep into the tissue, and easier installation and removal, while allowing for customization to accommodate individual patient needs, enhancing the treatment of infected prosthetic knee joints.

Implementation Method 1

The antibiotic in the spacer leaches out over time to treat the infection

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8974538B2Orthopedic spacer

Publication Date: 2015.03.10 TEENY STEVEN M

AI summary

A temporary knee replacement assembly and kit includes a tibial plate that attaches to the tibia, a tibial rod that extends through the plate into the medullary cavity and abuts the plate. A femoral plate attaches to the femur, and a femoral rod extends through the second plate into the femur medullary cavity and abuts the plate. A locking spacer connects the two rods. The spacer may be length adjustable or may be provided in multiple sizes for length selection. One or both of the rods may include a bone cement/antibiotic coating to provide antibiotic treatment to the tissue. The kit may include multiple tibial and femoral rods, multiple tibial and femoral plates, and multiple locking spacers, to accommodate different applications.