Expandable Coupling Sleeve for Self-Locking Prosthesis Connections
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Solution Overview
Problem
The challenge in hip endoprosthetics is creating a secure and long-term stable cone insertion connection between prosthetic components, especially when cone geometries are damaged or non-standard, leading to stress concentrations and potential fractures, and existing adapters struggle to maintain a stable connection due to tolerance deviations and non-standardized dimensions.
Innovation Solution
A coupling device featuring an expandable radial sleeve with a conically tapering inner wall and a male taper, which forms a self-locking press fit by widening when the cone of a prosthesis component is inserted, allowing for secure connection even with flawed or non-standard cones, and includes features like slots for radial expandability and a bead-groove mechanism for secure positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a standard cone insertion connection is used between prosthetic components, then the connection is simple and easy to manufacture, but stress concentrations occur when cone geometries are damaged or non-standard, leading to potential fractures
Solution Approach 1:
The patent introduces an adapter sleeve as an intermediary component between the damaged/non-standard cone and the replacement joint head. This adapter sleeve has a conical outer surface that interfaces with the existing cone geometry, while its inner surface provides a standardized interface for the new joint head, thereby mediating the connection and eliminating stress concentrations without requiring complete prosthesis replacement
Solution Approach 2:
The adapter sleeve modifies the geometric parameters of the cone connection by providing a transitional conical surface with optimized dimensions and angle. This parameter change allows the connection to accommodate damaged or non-standard cones while maintaining proper stress distribution and connection integrity
2Reliability
If adapter sleeves are used to connect replacement joint heads to existing shafts, then complete prosthesis replacement is avoided, but tolerance deviations and non-standardized dimensions lead to unstable connections
Solution Approach 1:
The adapter sleeve is designed with universal applicability to work with various existing cone geometries and shaft configurations. By providing a standardized interface on one end and adaptive conical surfaces on the other, it serves multiple functions: accommodating different cone sizes, compensating for tolerance deviations, and ensuring stable connections across different prosthesis systems
3Reliability
If the cone surface quality is degraded after joint head removal, then stress concentrations cause fractures in replacement joint heads, but complete explantation of the shaft increases surgical complexity and recovery time
Solution Approach 1:
The adapter sleeve acts as a protective intermediary layer between the degraded cone surface and the replacement joint head. It distributes stresses uniformly across its conical surface, preventing stress concentrations that would otherwise cause fractures in the new joint head, thereby enabling retention of the existing shaft and reducing recovery time
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 solution enables a long-term stable and secure press fit between prosthetic components, reducing the need for complete replacements, minimizing stress concentrations, and allowing for uniform force distribution, thereby reducing recovery times and improving patient outcomes.
Implementation Method 1
a self-locking press fit between the cone of the first prosthesis component and the coupling device can be established
Implementation Method 2
the expansion sleeve is designed for receiving the cone of the first prosthesis component and is designed so as to be expandable radially outwardly
Data Source
AI summary
A coupling device is for connecting prosthesis components by a self-locking press fit on an end, formed as a cone, of a first prosthesis component that is inserted in bone tissue. The coupling device has an outer coupling body with a socket having a conically tapering inner wall, and an expansion sleeve having a lateral surface forming a male taper and an operative forming a female tape. The expansion sleeve is mounted in the socket so as to be rotatable about the longitudinal axis thereof, and receives the cone. The expansion sleeve is expandable radially outwardly to form the self-locking press fit, such that the expansion sleeve widens radially when the cone is inserted into the expansion sleeve. As a result, the self-locking press fit between the cone of the first prosthesis component and the coupling device is established.