Modular Knee Prosthesis Distal Offset Joint Line
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Solution Overview
Problem
Standard knee prostheses often fail to optimally position the joint line and size the metaphyseal sleeve due to bone defects and resection requirements, leading to instability and potential revision surgeries.
Innovation Solution
A modular knee prosthesis system with a distal femoral component and adjustable metaphyseal members, including sleeves and shims, that allow for optimal sizing and positioning of the joint line by creating frictional locks at different positions on the stem, enabling the use of an optimally sized metaphyseal sleeve on a healthy bone bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard knee prostheses are used, then the implant can be installed quickly, but the joint line positioning and metaphyseal sleeve sizing cannot be optimized, leading to instability
Solution Approach 1:
The metaphyseal sleeve is divided into multiple modular components that can be selectively assembled. Different sized metaphyseal sleeves and stem adapters can be combined to achieve optimal joint line positioning and metaphyseal fill, resolving the contradiction between stability and complexity by allowing customization only when needed.
Solution Approach 2:
The system provides dynamic adjustability through multiple sizing options and configurable assemblies. Surgeons can select from various metaphyseal sleeve sizes and stem adapter configurations to optimize the joint line position and metaphyseal support, enabling the prosthesis to adapt to different bone anatomies and defect sizes.
2Ease of operation
If additional bone removal is performed to accommodate standard prostheses, then the prosthesis can be installed, but bone stock is depleted and revision surgery may be required
Solution Approach 1:
The system offers multiple sizing parameters including different metaphyseal sleeve lengths, diameters, and configurations. This allows surgeons to select components that match the patient's existing bone anatomy without requiring additional bone removal, thereby simplifying the surgical procedure while preserving bone stock.
3Reliability
If metaphyseal cavitary defects are present, then bone support is compromised, but standard implants cannot adequately fill the defects
Solution Approach 1:
The metaphyseal sleeve system is segmented into multiple size options and configurable components. Different sized sleeves can be selected to adequately fill various sizes of metaphyseal cavitary defects, providing appropriate bone support and adaptability to different defect geometries.
Solution Approach 2:
The modular metaphyseal sleeve system serves multiple functions: it provides metaphyseal support, fills cavitary defects of varying sizes, enables optimal joint line positioning, and can be configured with different stem adapters. This multi-functionality allows a single system to address diverse bone defect scenarios.
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
This system allows for flexible optimization of the joint line and metaphyseal sleeve positioning, enhancing the stability and longevity of the prosthetic implant by accommodating varying bone anatomy without the need for additional bone removal, thereby reducing revision surgeries.
Implementation Method 1
an inner surface defining a tapered bore sized and shaped to be mountable on the stem of the distal femoral component and to create a frictional lock between the stem of the distal femoral component and the metaphyseal member
Data Source
AI summary
A modular knee prosthesis system includes a femoral component having a stem and a sleeve. The system is modular, and provides the surgeon with the option of distally offsetting the joint line by controlling the relative axial positions of the stem and the sleeve. Alternative options include providing sleeves with tapered bores of different diameters, providing a shim to be placed between the sleeve and the stem and providing the stems as adapters having different diameters.