Joint Prosthesis Anchoring Element Rotation Mechanism
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Solution Overview
Problem
Existing joint prostheses, such as meniscus implants, face challenges in durable fixation under rotational and other stresses, as they rely heavily on polymer cords that can break due to rubbing against bone, leading to loose implants with no biological integration.
Innovation Solution
A joint prosthesis assembly featuring an anchoring element made of a biocompatible non-resorbable material that allows rotation of the prosthesis body, reducing forces on the implant by translating shear forces to the anchoring element, which can be made of a different material, thereby enhancing durability and integration with the bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-resorbable meniscus prosthesis is fixed using polymer cords attached to end plugs, then the prosthesis can be anchored to the tibial plateau, but the polymer cords break due to rubbing against bone, leading to loose implants
Solution Approach 1:
The invention extracts the problematic polymer cord from the fixation system and replaces it with a metal cable that has superior mechanical properties. The metal cable is routed through the tibial plateau bone rather than rubbing against the bone surface, eliminating the wear mechanism that caused polymer cord failure.
Solution Approach 2:
The metal cable acts as an intermediary element between the prosthesis and the bone. Instead of the polymer cord directly contacting and rubbing against the bone surface, the cable is embedded within the bone tunnel, using the bone itself as a protective conduit that eliminates friction and wear.
2Stability of the object's composition
If the prosthesis is rigidly fixed to prevent rotation, then stability is improved, but rotational stresses cause breakage of fixation elements
Solution Approach 1:
The invention introduces dynamic capability to the fixation system by allowing controlled rotation of the prosthesis around the metal cable axis. This dynamic design accommodates physiological rotational movements of the knee joint, preventing stress concentration and cable breakage that would occur with rigid fixation.
Solution Approach 2:
The invention changes the fixation parameter from rigid immobilization to controlled rotational freedom. The metal cable fixation system allows the prosthesis to rotate within a defined range, transforming the fixation from a static constraint to a dynamic system that adapts to joint movement.
3Ease of manufacture
If polymer cords are used for fixation, then implantation is simpler, but the cords lack resistance to rubbing forces and fail over time
Solution Approach 1:
The invention employs composite material strategy by combining metal cable (high strength, wear-resistant) with the polymer prosthesis body. The metal cable provides the necessary mechanical strength and wear resistance for fixation, while the polymer prosthesis maintains its ease of implantation and biocompatibility.
Data Source
AI summary
A joint prosthesis assembly, includes a joint prosthesis body (1) made of a first biocompatible non-resorbable material and an anchoring element (2-5) made of a second biocompatible non-resorbable material. The anchoring element (2-5) is arranged to allow rotation of an end portion of the joint prosthesis body (1) with respect to the anchoring element (2-5) when in situ.