Elbow Prosthesis Hermetic Seal for Wear Containment
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Solution Overview
Problem
Existing elbow prostheses suffer from backside wear, where polyethylene inserts wear not only on intended surfaces but also on metal contact surfaces, leading to wear products escaping into surrounding tissues and triggering immune responses that cause prosthesis loosening.
Innovation Solution
The elbow prosthesis design features a forearm stem with a head and upper arm stem connected via a shaft, incorporating a pipe section insert with an outer cover and disc-shaped covering plates, made of UHMWPE or HxUHMWPE, welded to form a hermetic seal, preventing wear products from escaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene inserts are used to create wear surfaces in elbow prostheses, then the wear surfaces can be designed with good friction properties, but backside wear occurs where wear products escape into surrounding tissues causing immune response and prosthesis loosening
Solution Approach 1:
The prosthesis is divided into multiple components: a metal shaft, a polyethylene insert, and a metal outer cover. This segmentation allows the wear-generating polyethylene insert to be isolated within the hermetic outer cover, preventing wear products from escaping to surrounding tissues while maintaining the functional wear surface between the insert and shaft.
Solution Approach 2:
The hermetic outer cover acts as an intermediary barrier between the wear interface (shaft and polyethylene insert) and the surrounding biological environment. This intermediate structure captures and contains wear products, preventing them from reaching the immune system and causing adverse reactions.
2Ease of manufacture
If form-locking bonds are used to attach polyethylene components to metal prosthesis elements, then the components can be securely mounted, but the form-locking joints do not prevent wear product formation and escape
Solution Approach 1:
The hermetic outer cover serves as an intermediary containment structure that surrounds the form-locking joint between the polyethylene insert and metal shaft. While the form-locking bond maintains its simple mounting function, the outer cover prevents wear products generated at this interface from escaping, thus resolving the contradiction between easy assembly and wear product containment.
Solution Approach 2:
The outer cover functions as a flexible yet hermetic shell that encapsulates the entire joint assembly. This thin-walled structure maintains the simplicity of the form-locking connection while providing a continuous barrier against wear product escape.
3Reliability
If chambers are formed in the joint to capture wear shiver, then wear products can be isolated, but the openings of the chambers break the continuous joint surface and shiver still damages the joint surface
Solution Approach 1:
The hermetic outer cover acts as an intermediary containment structure that completely encloses the joint assembly. Unlike discrete chambers with openings, the continuous outer cover maintains the integrity of the joint surface while still capturing wear products through its hermetic seal, thus preserving both surface continuity and wear capture functionality.
Solution Approach 2:
The outer cover is a continuous thin-walled shell that envelops the entire joint without breaking the surface continuity. This hermetic enclosure captures wear products throughout the joint volume while maintaining an unbroken protective barrier, solving the contradiction between wear capture and surface integrity.
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 design minimizes micro-movements and hermetically isolates wear products, reducing backside wear and preventing them from entering surrounding tissues, thus reducing immune response and prosthesis loosening.
Implementation Method 1
an outer cover covering the head is attached to the insert, on which a first covering plate with a first hole and a second covering plate with a second hole both having the same diameter as the diameter of the axial hole of the insert) formed as a pipe section are oppositely arranged, and a forearm stem opening is formed, and the flange of the holes is welded to the flange) of the axial hole, the flange of the opening of the forearm stem is welded to the forearm stem along the respective flanges by a continuous seam.
Data Source
AI summary
The invention relates to an elbow prosthesis implant having a forearm stem (1) an upper arm stem (2), and a shaft (3) fixed to the upper arm stem (2) hingedly connecting the stems (1, 2) to each other, and an insert (9) is arranged between the shaft (3) and an inner surface (1c) of a hole (1a). The insert has an axial hole (10), and an outer cover (4) is attached to the insert (9), on which first (31) and second covering plates (32) are oppositely arranged. and a forearm stem opening (43) is formed, and the flange (31p, 32p) of the holes (31f, 32f) is welded to the flange (10p) of the axial hole (10), the flange (43p) of the opening (43) of the forearm stem (1) is welded to the forearm stem (1) along the respective flanges (31p, 32p, 10p, 43p) by a continuous scam.