Hinged Knee Prosthesis Variable Axis Rotation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hinged knee prostheses face challenges in evenly distributing weight loads and replicating the natural movement of the knee joint, particularly in cases where collateral ligaments are damaged, leading to instability and inadequate load transfer.
Innovation Solution
The design incorporates a hinge assembly with elongated slots in the femoral component and a piston with a hinge pin that translates along these slots, allowing for a variable axis of rotation and even load distribution across the bearing component and tibial tray, mimicking natural knee movement and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a hinge mechanism is used to couple the femoral component to the tibial component, then stability is provided, but the hinge mechanism must support load transfer which increases stress on the hinge
Solution Approach 1:
A bearing component is introduced as an intermediary element between the femoral component and tibial component. The bearing includes a bearing surface that transfers loads from the femur to the tibia, mediating the load transfer function and allowing the hinge mechanism to focus on providing stability through motion constraint rather than supporting full joint loads
Solution Approach 2:
The prosthesis is divided into distinct functional components: the hinge assembly (with piston, hinge pin, and elongated slots) responsible for stability and motion control, and the bearing component responsible for load transfer. This segmentation allows each component to optimize its specific function without compromising the other
2Device complexity
If a fixed axis hinge is used, then the hinge mechanism is simple, but it does not replicate natural knee movement which involves complex motions
Solution Approach 1:
The hinge mechanism transitions from a fixed axis design to a dynamic variable axis design. The elongated slots in the femoral component allow the hinge pin to translate along the slots during flexion and extension, creating a moving axis of rotation that adapts to the natural kinematics of the knee joint while maintaining relative simplicity in the mechanism's construction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A hinged orthopaedic knee prosthesis (10) includes a femoral component (12), a tibial component (18), and a bearing component (16) positioned between the femoral and tibial components. A hinge assembly (14) is coupled to the femoral component to constrain the movement of the femoral component relative to the tibial component.