Anterior Stabilized PCL Retaining Knee Prosthesis Cam Mechanism
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Solution Overview
Problem
Current total knee arthroplasty (TKA) devices either sacrifice the anterior cruciate ligament (ACL) or remove both cruciate ligaments, leading to paradoxical movement, reduced proprioception, and insufficient performance for active individuals due to lack of anterior stability and proprioception.
Innovation Solution
A knee prosthesis design that retains the posterior cruciate ligament (PCL) and includes a tibial component with an anterior post and a femoral component with a cam mechanism, where the cam slides along the post's posterior surface from 0 to 40 degrees of flexion to restrict anterior subluxation, allowing the PCL to take over beyond 40 degrees, maintaining natural kinematics and proprioception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ACL is removed and PCL is retained (cruciate-retaining TKA), then the PCL can be preserved for proprioception, but the knee exhibits paradoxical movement and anterior subluxation during certain activities
Solution Approach 1:
The patent introduces a cam mechanism as an intermediary element between the femoral and tibial components. This cam provides anterior stability by contacting the tibial post, preventing paradoxical movement while allowing the PCL to remain intact for proprioception. The cam acts as a mediator that compensates for the lack of ACL without requiring PCL removal.
2Stability of the object's composition
If both ACL and PCL are removed and substituted with cam and post mechanism (posterior stabilized TKA), then anterior stability is provided, but proprioception is reduced and natural knee function is compromised
Solution Approach 1:
The patent extracts only the necessary stabilizing function from the traditional posterior stabilized design. Instead of removing both cruciate ligaments, it removes only the ACL function while retaining the PCL. The cam and post mechanism is used selectively to provide anterior stability only when needed, allowing the PCL to remain intact for proprioception and natural knee function.
3Stability of the object's composition
If cam and post mechanism remains engaged throughout flexion and extension, then continuous anterior stability is provided, but the likelihood of failure and wear increases
Solution Approach 1:
The patent implements a dynamic engagement system where the cam and post mechanism engages only when needed (during early flexion up to 40 degrees) and disengages during deeper flexion. This dynamic behavior reduces continuous contact and wear between components while maintaining anterior stability when required. The geometry of the cam and post allows automatic engagement and disengagement based on knee position.
Data Source
AI summary
A knee prosthesis that includes a tibial component and femoral component. The tibial component includes an articular surface, a posterior portion and an anterior portion. The posterior portion includes a recess for receipt of a posterior cruciate ligament. The anterior portion includes a post extending therefrom. The post includes a posterior surface. The femoral component includes a condylar portion and an intercondylar portion. The intercondylar portion includes a posterior recess for receipt of the posterior cruciate ligament, a cam, and an engagement recess for receipt of the post. The cam includes a sliding surface and is disposed between the engagement recess and posterior recess. The sliding surface of the cam slides along the posterior surface of the post for restricting anterior subluxation of a femur bone when the articular surface and the condylar portion articulates through flexion of a knee joint.