Modular Knee Prosthesis Inserts for ACL and PCL Kinematics
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Solution Overview
Problem
Existing total knee replacements (TKR) inadequately substitute the function of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), leading to reduced functionality and difficulty in adjusting to physical activity post-surgery.
Innovation Solution
A modular knee joint prosthesis with interchangeable femoral and tibial inserts that simulate the function of both ACL and PCL, allowing for a more anatomically correct knee replacement by mimicking the kinematics of a healthy knee through a system of gears and tracks that guide motion between flexion and extension positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a post and cam mechanism is used to substitute the PCL, then the PCL function is partially replaced, but the ACL function remains inadequately substituted and normal knee kinematics are not achieved
Solution Approach 1:
The invention divides the ligament substitution function into separate components: a post-and-cam mechanism for PCL substitution and a separate artificial ACL component with bone anchors for ACL substitution. This segmentation allows each mechanism to be optimized independently for its specific function, resolving the contradiction between reliable PCL substitution and adequate ACL substitution.
Solution Approach 2:
The invention introduces an artificial ACL component as an intermediary element that bridges the femoral component and tibial component, providing the missing ACL function. This intermediary structure enables proper knee kinematics by replicating the natural ACL's role in preventing anterior tibial translation and providing rotational stability.
2Ease of manufacture
If the ACL is removed in most TKR cases, then the surgery is simplified, but the reconstructed knee lacks normal kinematics and requires extensive physical therapy adjustment
Solution Approach 1:
The artificial ACL component with bone anchors serves itself by directly replacing the removed ligament's function without requiring complex external mechanisms. The component autonomously provides anterior stability and rotational control, allowing the knee to naturally regain normal kinematics without extensive physical therapy intervention to compensate for the missing ACL.
3Device complexity
If a crude cam and post mechanism is used for ACL substitution, then the device complexity is reduced, but the anterior side contact is limited to only 0-20 degrees of flexion
Solution Approach 1:
The invention replaces the static, limited-contact cam and post mechanism with a dynamic artificial ACL component that actively engages across the full range of motion. The bone-anchored construct moves with the knee joint, maintaining contact and functional control from full extension through flexion, thereby expanding the flexion range contact while keeping the device relatively simple.
Data Source
AI summary
A modular knee joint prosthesis is configured to move between an extended position and a flexion position. The modular knee joint prosthesis includes a femoral component that is configured to be mounted to a femur. The femoral component has a first cutout or opening in a central region thereof for receiving a femoral insert. The modular knee joint prosthesis also includes a tibial component that is configured to (i) be mounted either directly or indirectly to a tibia, and (ii) engage the femoral component. The tibial component has a second cutout or opening in a central region thereof for receiving a tibial insert. A kit includes the modular knee joint prosthesis, at least two of the femoral inserts having different geometries, and at least two of the tibial inserts having different geometries.