Modular Hinge Knee Prosthesis Offset Flexion Centers
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Solution Overview
Problem
Current total knee arthroplasty (TKA) prostheses, particularly hinge knee prostheses, fail to accurately replicate natural patellofemoral kinematics, leading to unnatural joint movement and restricted range of motion, which can be painful and compromise patient satisfaction.
Innovation Solution
A total knee prosthesis design featuring a tibial component with a baseplate and protruding portion, a femoral component with offset flexion centers, and a coupling component with a bearing and articulating portion, allowing for natural patellar tilt angles and enhanced range of motion by positioning the articular surfaces to mimic the kinematics of a natural knee.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a one-degree-of-freedom hinge mechanism is used to provide stability, then knee stability is improved, but natural knee kinematics become restricted
Solution Approach 1:
The hinge mechanism is segmented into multiple independent components: a femoral component with cam structure, a tibial component with post structure, and a coupling component with bearing. This segmentation allows each component to perform its specific function while collectively providing both stability and natural kinematics. The cam structure provides rotational freedom, the post structure provides stability during flexion, and the bearing allows for natural patellofemoral movement.
Solution Approach 2:
The hinge mechanism transitions from a static one-degree-of-freedom design to a dynamic multi-functional system. The cam and post structures enable the knee to adapt its degrees of freedom based on the flexion angle: at extension, the cam allows rotation; during flexion, the post engages to provide stability; and the bearing allows natural patellar movement. This dynamic behavior resolves the contradiction between stability and natural kinematics.
2Stability of the object's composition
If existing hinge knee prostheses focus on tibiofemoral articulation, then tibiofemoral stability is improved, but patellofemoral kinematics become unnatural
Solution Approach 1:
The prosthesis is divided into distinct functional segments: the tibiofemoral joint components (cam and post structures) and the patellofemoral joint components (articulating portion with bearing). This segmentation allows independent optimization of each joint's function. The tibiofemoral components provide stability through the cam-post mechanism, while the patellofemoral components provide natural kinematics through the bearing and articulating surfaces.
Solution Approach 2:
The coupling component serves multiple functions: it connects the femoral and tibial components, provides the bearing surface for natural patellar movement, and transmits forces between the joints. This multi-functionality resolves the contradiction by integrating both tibiofemoral stability and patellofemoral natural kinematics into a single unified structure.
Data Source
AI summary
A total knee prosthesis including a tibial component having a baseplate portion and a protruding portion extending from the baseplate portion is disclosed. An axle is connectable to the tibial component directly or indirectly. A femoral component has an articular surface and an opening for receipt of the axle. The opening defines a pivot center about which the femoral prosthesis rotates. The articular surface has a posterior portion having a first flexion radius defining a first flexion center. The first flexion center is offset from the pivot center a distance substantially equal to a product of a constant and the first flexion radius.