Artificial Knee Joint Dual Sliding Surface Rollback
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Solution Overview
Problem
Conventional artificial knee joints fail to replicate the natural rollback movement of the knee joint, with insufficient rollback in deep flexion, leading to potential contact between the femoral component and tibia, and an inconsistent rollback ratio across different flexion angles.
Innovation Solution
The artificial knee joint design features a femoral component with a medial and lateral condyle, and a tibial plate with specific sliding surfaces that change contact positions as the knee flexes, allowing for a smaller rollback in slight flexion and a larger rollback in deep flexion, mimicking the natural knee's movement by positioning the fourth sliding surface posterior to the third sliding surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional artificial knee joint design with a single sliding surface is used, then the structure is simple, but the rollback amount is insufficient in deep flexion and the rollback ratio remains constant
Solution Approach 1:
The single sliding surface is divided into multiple sliding surfaces (first sliding surface, second sliding surface, third sliding surface, and fourth sliding surface) positioned at different locations. Each sliding surface engages at different flexion angles, enabling the femoral component to achieve appropriate rollback amounts throughout the range of motion while maintaining structural simplicity through modular surface design.
2Ease of operation
If the rollback amount is increased in deep flexion, then the natural movement is improved, but the risk of femoral component contact with tibia increases
Solution Approach 1:
The knee joint design incorporates dynamic engagement of different sliding surfaces based on flexion angle. The first and second sliding surfaces engage during slight to moderate flexion, while the third and fourth sliding surfaces engage during deep flexion. This dynamic transition allows the rollback amount to increase naturally with flexion angle while maintaining safe separation between the femoral component and tibia through geometric constraints of the sliding surfaces.
3Ease of manufacture
If a single sliding surface configuration is used, then the manufacturing is simple, but the rollback ratio cannot vary with flexion angle
Solution Approach 1:
Different sliding surfaces are positioned at specific locations with distinct geometric properties. The first sliding surface and third sliding surface engage for slight flexion with a first rollback ratio, while the second sliding surface and fourth sliding surface engage for deep flexion with a second rollback ratio. This local differentiation of surface properties enables the rollback ratio to vary appropriately with flexion angle while maintaining manufacturing simplicity through standardized surface geometries.
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 design ensures the artificial knee joint operates similarly to a natural knee, with a lower rollback ratio in slight flexion and a higher ratio in deep flexion, reducing the risk of femoral component dislocation and improving stability and flexibility.
Implementation Method 1
a third sliding surface which is formed at a posterior surface of the post and with which the first sliding surface is rotatably and slidably in contact
Implementation Method 2
a fourth sliding surface which is formed posterior to the post and with which the second sliding surface is rotatably and slidably in contact
Data Source
AI summary
An artificial knee joint comprising a femoral component and a tibial plate is provided. The femoral component includes a medial condyle, a lateral condyle, a first sliding surface for coupling the medial and lateral condyles, while leaving an opening therebetween, and a second sliding surface above the first sliding surface. The tibial plate includes a medial fossa, a lateral fossa, a post insertable into the opening, a third sliding surface which the first sliding surface contacts at a posterior surface of the post, and a fourth sliding surface which the second sliding surface contacts behind the post. The artificial knee joint is configured to move in a first sliding state in which the first sliding surface is in contact with the third sliding surface, or a second sliding state in which the second sliding surface is in contact with the fourth sliding surface, according to a flexion angle.