Universal Knee Prosthesis Extractor With Scissor Mechanism
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Solution Overview
Problem
Current ejectors and jigs for knee endoprostheses lack stable non-positive anchoring and inefficient force transmission, making it difficult to remove prosthetic components during revision surgeries without causing secondary damage to the bony bed or requiring unsatisfactory osteotomies.
Innovation Solution
A universal extractor with a scissor mechanism, clamping jaws, and a T-piece with a slotted rod, featuring adjustable clamping jaws and a knurled nut for secure anchoring and optimal force development, allowing for stable, orthograde fixation and easy release of knee prosthesis components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current ejectors and jigs are used for knee endoprostheses, then the removal process can be performed, but stable non-positive anchoring cannot be achieved and force transmission is inefficient
Solution Approach 1:
The clamping jaws are designed with a curved shape that matches the curvature of the prosthesis component surface. This curved geometry enables stable non-positive anchoring by conforming to the rounded edges of the prosthesis, allowing the extractor to firmly grip and securely anchor to the component during removal operations.
Solution Approach 2:
The scissor mechanism is integrated within the T-piece structure, with the clamping jaws nested at the distal end of the scissor mechanism. This nested arrangement allows compact construction while maintaining full functionality, enabling stable anchoring through the integrated clamping system and efficient force transmission through the nested mechanical components.
2Force
If sledge hammers are used for explanting joint components, then removal force can be applied, but unsatisfactory force transmission occurs
Solution Approach 1:
The T-piece with slotted rod acts as an intermediary between the hammer impact and the prosthesis component. The slotted rod provides a guided path for force transmission, directing the impact force efficiently from the hammer through the T-piece to the prosthesis, replacing the inadequate direct force transmission of sledge hammers with a controlled mechanical interface.
Solution Approach 2:
The scissor mechanism provides dynamic force multiplication and directional control. As the hammer strikes the T-piece, the scissor mechanism dynamically translates this impact force into controlled extraction force on the prosthesis, optimizing force transmission efficiency while maintaining the ability to apply substantial explantation force.
3Productivity
If firmly integrated prosthesis components are removed directly, then removal can be attempted, but secondary damage to the bony prosthesis bed occurs
Solution Approach 1:
The extractor enables preliminary loosening action before complete removal. The stable anchoring and controlled force application allow the prosthesis to be gradually loosened from its firm integration, reducing anchoring surface area progressively. This preliminary action prevents sudden forceful extraction that would cause secondary damage to the bony prosthesis bed.
4Adaptability or versatility
If a universal extractor is designed to accommodate different prosthesis sizes, then versatility is improved, but device complexity increases
Solution Approach 1:
The extractor is segmented into modular components: the T-piece with slotted rod, the scissor mechanism, and the clamping jaws. This segmentation allows the device to accommodate different prosthesis sizes and geometries while maintaining a relatively simple overall structure. The modular segments can be adjusted and reconfigured for different extraction scenarios without requiring complete device redesign.
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 secure, non-damaging removal of knee prosthesis components by providing stable anchoring and controlled force transmission, facilitating revision surgeries and re-implantation while being reusable and resterilizable.
Implementation Method 1
eyebolt with knurled nut
Implementation Method 2
scissor mechanism with clamping jaws
Implementation Method 3
shovel-like, approximately V- to U-shaped form allows a firm, self-centering fixation even on curved prosthesis edges
Data Source
Figure 1
AI summary
The invention relates to a universal extractor for total endoprostheses (TEP) of the knee joint. The object of the invention, namely to make available a universal extractor for artificial knee joints that avoids the disadvantages of the prior art, is achieved by the fact that the universal extractor comprises the following parts: a T-piece (1) with an extraction plate (11) and with a securing arm (8), said securing arm (8) being fork-shaped and slotted at its distal end (9) and supporting the extraction plate (11) at its proximal end; a scissor mechanism (7) with clamping jaws (71) located at its free distal ends, said securing arm (8) holding the scissor mechanism (7) by means of a securing pin (74) about which the scissor mechanism (7) can move; and an eyebolt (72) which is mounted on the proximal end of the scissor mechanism (7) and has a knurled nut (73), the eyebolt (72) being adjustable and connecting the ends of the scissor mechanism (7) to each other, so as to permit fixing or release of the clamping jaws (71), which have a shovel-shaped, U-shaped to V-shaped geometry.