Modular Knee Prosthesis with Common-Geometry Metaphyseal Sleeves
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Solution Overview
Problem
In knee replacement surgeries, especially revision surgeries, standard knee implants often fail to adequately address metaphyseal cavitary defects, leading to loosening and instability of the prosthetic implant due to insufficient bone support, requiring additional bone preparation for larger sleeves, which complicates the procedure.
Innovation Solution
A modular knee prosthesis system with metaphyseal sleeves of varying lengths sharing a common geometry, allowing for optimal positioning of the joint line without additional bone preparation, using tapered stems and sleeves with frictional locks to ensure stability and compatibility across different sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard knee implants are used, then the procedure is simple, but they fail to adequately address metaphyseal cavitary defects leading to loosening and instability
Solution Approach 1:
The prosthesis system is divided into modular components including a base implant and separate metaphyseal sleeves. The sleeves can be selectively added to address cavitary defects in the metaphysis, allowing the implant to be segmented into functional zones (articulating surfaces, stem, and metaphyseal support) that can be independently optimized and assembled.
Solution Approach 2:
The metaphyseal sleeves are designed to fit over the stem of the base implant, creating a nested structure. The sleeves contain internal channels that receive the stem, similar to nested dolls, providing additional bone support and filling cavitary defects while maintaining a compact, integrated structure that doesn't significantly increase overall complexity.
2Reliability
If larger sleeves are used to fill metaphyseal defects, then bone support is improved, but additional bone preparation is required which complicates the procedure
Solution Approach 1:
The metaphyseal sleeves are pre-formed with the correct geometry and internal channels during manufacturing. The stem is designed with a corresponding external geometry that matches the sleeve channels. During surgery, the stem is simply inserted into the sleeve without requiring additional bone preparation or modification, as all preparatory actions were completed in advance during fabrication.
3Adaptability or versatility
If multiple sizes of metaphyseal sleeves are used, then adaptability to different defects is improved, but device complexity increases
Solution Approach 1:
Different metaphyseal sleeves are designed with locally optimized qualities to address specific defect patterns. Each sleeve variant has customized features such as varying lengths, different channel configurations, and specialized geometries tailored to fit specific cavitary defect locations and sizes, allowing targeted treatment without requiring complete redesign of the entire prosthesis system.
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
Enables flexible optimization of the joint line position and efficient seating of metaphyseal sleeves on a healthy bone bed, reducing the need for additional bone preparation and enhancing the stability and longevity of the prosthetic implant.
Implementation Method 1
tapered stems and sleeves with frictional locks to ensure stability
Data Source
AI summary
A modular knee prosthesis system includes a femoral component having a stem, a plurality of different sizes of sleeves mountable on the stem, and a plurality of different sizes of augments mountable on the femoral component. The system is modular, and provides the surgeon with the option of distally offsetting the joint line by selecting the size of sleeve that will provide the desired joint line. The different sizes of sleeves have different axial lengths but share a common geometry along a substantial part of their lengths so that the same bone cavity will accept multiple sizes of sleeves.