Antimicrobial Bone Cement with Segmented Powder for Uniform Elution

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Solution Overview

Problem

Current antibiotic impregnated spacer implants made from acrylic bone cement lack uniformity in elution, mechanical, and handling properties due to variable antibiotic concentrations and mixing methods, leading to unpredictable performance in orthopedic surgical applications.

Innovation Solution

A two-part bone cement composition with a premixed powder component containing gentamicin and vancomycin, along with a liquid monomer, is used to create a temporary spacer implant, providing a consistent viscosity profile that allows for predictable elution and handling properties without the need for pre-chilling or excess liquid, suitable for use in orthopedic surgical procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If antibiotics are hand-mixed in bone cement with varying concentrations, then the antibiotic dose can be adjusted, but uniformity of elution, mechanical properties, and handling properties deteriorates

Engineering Contradiction:

Improveantibiotic dose adjustmentVSAvoiduniformity of elution and mechanical properties

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The bone cement is divided into two separate components: a powder component containing acrylic polymer and antibiotic sources, and a liquid component containing monomer. This segmentation allows for consistent mixing ratios and predictable elution properties while maintaining the ability to adjust antibiotic doses through controlled formulation of the powder component.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent specifies precise parameter ranges for the powder to liquid ratio (from about 1:1 to about 2:1 by weight) and antibiotic concentrations (gentamicin from 5-6% and vancomycin from 4-5% of powder component weight). By controlling these parameters within defined ranges, the invention achieves uniform elution and mechanical properties while allowing dose adjustment through formulation selection.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If bone cement viscosity is reduced by chilling, then the cement can be used, but the handling properties and working time are affected

Engineering Contradiction:

Improvecement usabilityVSAvoidhandling properties and working time

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

The patent formulates the bone cement with specific powder to liquid ratios and antibiotic concentrations that inherently provide suitable viscosity at room temperature, eliminating the need for chilling. The powder component contains acrylic polymer and radical initiator in controlled amounts to ensure proper flow characteristics and working time without temperature modification.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If powder to liquid ratio is altered to obtain suitable viscosity, then the cement can be mixed, but elution, mechanical, or handling properties are altered in unpredictable ways

Engineering Contradiction:

Improveviscosity suitabilityVSAvoidpredictability of elution and mechanical properties

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent establishes specific parameter ranges for the powder to liquid ratio (from about 1:1 to about 2:1 by weight) and antibiotic concentrations that simultaneously achieve suitable viscosity and predictable elution properties. The controlled formulation ensures that within these ranges, the cement maintains consistent mechanical and handling properties while providing reliable antibiotic release.

Inventive Principle:

Principle #35Parameter changes

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 solution ensures a stable and predictable delivery of antibiotics, maintaining mechanical strength and handling properties, allowing for effective infection management and implantation procedures with reduced waste and improved clinical outcomes.

Implementation Method 1

The bone cement composition comprises a powder component including an acrylic polymer and a radical initiator. A liquid monomer component is also provided. A reaction of the powder polymer component and liquid monomer component provides a bone cement composition

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentUS8834772B2Antimicrobial methacrylate cements

Publication Date: 2014.09.16 BIOMET MFG LLC

AI summary

Bone cement compositions and methods of making two-part bone cements. The methods comprise transferring premixed powder and a liquid component into a receptacle, and mixing the powder component and the liquid component to form a cement composition. The premixed powder component comprises an acrylic polymer and a radical initiator. The bone cement is loaded with from about 5% to about 6% gentamicin by weight of the powder component, and from about 4% to about 5% vancomycin by weight of the powder component. The methods include filling a mold cavity with the bone cement composition to form a temporary spacer implant. The bone cement compositions provide a viscosity profile sufficient for the bone cement composition to flow within the mold cavity for an elapsed working time period of greater than about 6 minutes from the start of mixing at approximately 23° C.