Ceramic Joint Prosthesis Adapter Force Distribution
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Solution Overview
Problem
Existing joint prosthesis systems face issues with ceramic failure due to uneven force distribution, leading to cracking and premature revision surgery, especially when cone angles are unknown or damaged, causing complications during revision operations.
Innovation Solution
A joint prosthesis system with a conical adapter made of superelastic material, such as a nickel-titanium alloy, that concentrates force on a narrow surface area of the metal outer cone and distributes it over a large area on the ceramic inner cone, near the virtual center of the joint ball, using a convex bulge and resilient design to absorb forces and counteract tilting moments, ensuring even load distribution and maintaining contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coupling element contacts the entire conical surface of the metal neck and ceramic joint ball, then the force is distributed over the entire surface, but this leads to ceramic failure due to force application deviating from the center point
Solution Approach 1:
The adapter is divided into functionally distinct wall sections: an inner wall section with a convex circumferential bulge that contacts a narrow surface area on the metal outer cone, and an outer wall section with a conical surface that contacts the load-bearing area on the ceramic inner cone. This segmentation allows different parts of the adapter to perform different functions - concentrating force on the metal while distributing it appropriately on the ceramic.
Solution Approach 2:
The adapter features localized structural variations with different wall sections having distinct geometries and material properties. The inner wall section has a convex bulge for force concentration on the metal cone, while the outer wall section has a conical shape for force distribution on the ceramic cone. This local differentiation optimizes force transmission paths to protect the ceramic from damaging stress concentrations.
2Ease of operation
If the cone angle of the prosthesis neck is unknown or damaged, then the prosthesis socket must be extracted during revision operations, but this causes adverse consequences for the patient
Solution Approach 1:
The adapter is designed with elastic properties that allow it to accommodate variations in cone angle and diameter. The resilient wall section can deform elastically to adapt to different geometric parameters of the metal outer cone, enabling the adapter to function correctly even when the original cone dimensions are unknown or have changed due to damage or wear.
Solution Approach 2:
The adapter incorporates a resilient wall section that can dynamically adapt its shape and contact points based on the actual geometry of the metal outer cone. This dynamic adaptability allows the system to maintain proper force transmission without requiring precise pre-knowledge of cone parameters, simplifying revision operations.
3Strength
If the adapter concentrates force on a narrow surface area of the metal outer cone, then the metal can withstand the concentrated load, but the ceramic must also receive distributed force over a large area
Solution Approach 1:
The adapter serves as an intermediary component between the metal outer cone and the ceramic inner cone. It has an inner wall section that concentrates force on the metal cone and an outer wall section that distributes force over a large area on the ceramic cone. This intermediary structure allows the metal and ceramic components to interact in their optimal stress states without direct contact.
4Stability of the object's composition
If the resilient wall section prevents bulge caused by the convex circumferential bulge, then tilting moment is counteracted, but the adapter must maintain elastic contact with both the metal cone and ceramic inner cone
Solution Approach 1:
The resilient wall section acts as a counterbalancing element that prevents the convex circumferential bulge from causing excessive tilting moments. By providing elastic resistance, it counteracts the destabilizing effect of the bulge while maintaining the overall geometric stability of the adapter during force transmission.
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 effectively increases the service life of the prosthesis by reducing stress on the ceramic joint ball, allowing it to absorb forces near its center while relieving outer areas, preventing fractures and enabling precise fitting regardless of cone dimensions, thus minimizing the risk of revision surgery.
Implementation Method 1
a resilient wall section which firstly rests on the outer cone below the load-bearing area on the lower part to prevent a bulge caused by the convex peripherally shaped bulge generated tilting moment and later elastically against the inner cone of the joint ball
Implementation Method 2
the shaped body is made of a superelastic material, preferably a biocompatible shape memory alloy, for example nickel-titanium alloy, which shows a pronounced superelasticity, whereby the adapter undergoes a hysteresis depending on the stress level acting on it, which adapter returns to its original shape
Implementation Method 3
whereby the adapter undergoes a hysteresis depending on the stress level acting on it, which adapter returns to its original shape
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The invention relates to a joint prosthesis system, comprising a metal shaft (1), which is implanted in the femur, a throat (2) having an outer cone (3), a joint ball (5) made of ceramic and having an accommodation (6) for the throat (2), said accommodation comprising an inner cone (7), and a sheath-shaped adapter (4), which is arranged between the shaft (1) and the joint ball (5) in a clamping manner. Due to an exceptional elasticity and a special shaping of an inner and an outer wall section (9, 12) of the adapter (4), the application of force to a narrow surface region (11) on the metal outer cone (3) and the application of the force into the ceramic inner cone (7) is extensively concentrated on a load-bearing region (B) opposite the narrow surface region (11) within the largest mass expansion of the ceramic joint ball (5).