Modular Knee Prosthesis Metaphyseal Sleeve Design
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Solution Overview
Problem
Current knee prosthetic systems face challenges in optimizing the joint line position and sizing of metaphyseal sleeves, leading to potential loosening and instability due to cavitary defects in the metaphysis, which can require revision surgery.
Innovation Solution
A modular knee prosthesis system with multiple sized metaphyseal sleeves having the same geometry over a substantial portion of their axial lengths, allowing for optimal positioning and sizing without additional bone preparation, using tapered and stepped surfaces for secure frictional locking with the femoral and tibial components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metaphyseal sleeves with different geometries are used to fill cavitary defects, then the fit and stability in the metaphysis is improved, but the complexity of selecting and sizing components increases
Solution Approach 1:
The metaphyseal sleeve is designed with a universal geometry that can accommodate various bone conditions without requiring multiple specialized sleeve designs. The standardized geometry allows the same sleeve design to function effectively across different patient anatomies and defect types, reducing the complexity of component selection while maintaining reliable fixation.
Solution Approach 2:
Rather than changing the geometry of the metaphyseal sleeve, the invention changes the parameters of the accompanying augments (thickness, configuration) to adapt to different bone conditions. This allows the metaphyseal sleeve geometry to remain constant while still providing customized solutions for various cavitary defects through parameter adjustment of auxiliary components.
2Loss of substance
If the joint line is elevated to accommodate proximal resection, then bone loss is compensated, but the performance of the prosthetic knee system deteriorates
Solution Approach 1:
The metaphyseal sleeve acts as an intermediary component that allows the joint line to be maintained at the appropriate level despite proximal resection. By providing structural support and load transfer capability within the metaphysis, the sleeve enables the use of a standard femoral component position without compromising knee kinematics or ligament function, thus mediating between bone loss and prosthetic performance requirements.
Solution Approach 2:
The prosthesis is segmented into distinct components (femoral component, metaphyseal sleeve, augments) that can be independently optimized. The metaphyseal sleeve specifically addresses bone loss in the metaphysis while allowing the femoral component to maintain its optimal position for knee performance, separating the functions of bone reconstruction and joint mechanics.
3Adaptability or versatility
If multiple sized metaphyseal sleeves with same geometry are provided, then adaptability to different bone conditions is improved, but the quantity of components in the system increases
Solution Approach 1:
The system provides localized adaptation through augments of varying thicknesses and configurations that are added to the standardized metaphyseal sleeve. Rather than creating entirely different sleeve geometries for different bone conditions, the invention applies local modifications via augments to achieve the necessary customization, reducing the overall quantity of unique components required.
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 secure fixation, reducing the need for further bone preparation and potentially minimizing revision surgeries by providing a stable and customizable fit for varying bone conditions.
Implementation Method 1
an inner surface defining a tapered bore sized and shaped to be mountable on the stem of one of the implant components and to create a frictional lock between the stem and the first metaphyseal member
Implementation Method 2
using tapered and stepped surfaces for secure frictional locking with the femoral and tibial components
Data Source
Figure 1
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Figure 3~6
AI summary
A modular knee prosthesis system includes a femoral component (10) having a stem (16) and a plurality of different sizes of sleeves (24, 24A, 24B, 24C) mountable on the stem. 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.