ACL-Substituting Knee Prosthesis Crossbar Stability
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Solution Overview
Problem
The challenge in knee arthroplasty is recreating the stability and complex movements of a natural knee joint without the anterior cruciate ligament (ACL), which is often sacrificed, leading to difficulties in preventing anterior translation and rotational movements.
Innovation Solution
The development of knee prostheses that include a femoral component and a tibial component, designed to resist anterior and rotational movements in extension while allowing greater freedom in flexion, mimicking the ACL's function by using features like patello-femoral flanges, crossbars, and articulating surfaces that change shape and orientation to accommodate the posterior cruciate ligament (PCL).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ACL is sacrificed during knee arthroplasty, then the surgical procedure is simplified, but the stability against anterior translation and rotational movements is compromised
Solution Approach 1:
The patent creates artificial structures (crossbar, flanges, articulating surfaces) that copy and replicate the functional properties of the ACL. The crossbar with its specific geometry and articulating surfaces mimic the ligament's ability to resist anterior translation and rotation, providing stability without requiring the natural ligament
Solution Approach 2:
The patent divides the stability function into separate structural elements: the crossbar for anterior-posterior stability, the flanges for rotational control, and the articulating surfaces for guided movement. This segmentation allows each component to address specific stability requirements that would otherwise require the intact ACL
2Reliability
If the prosthesis is designed to resist anterior and rotational movements in extension, then stability in extension is improved, but freedom of movement in flexion is restricted
Solution Approach 1:
The patent employs dynamic geometric relationships where the articulating surfaces are configured to provide constraint in extension (resisting anterior translation and rotation) but allow natural movement in flexion. The surfaces are shaped so that their constraint function is angle-dependent, automatically adapting to the knee's position in space
Solution Approach 2:
The prosthesis design changes the effective constraint parameters based on knee angle. In extension, the articulating surfaces create geometric constraints that resist anterior translation and rotation. In flexion, the same surfaces allow greater freedom as the contact geometry changes, providing position-dependent stability
3Reliability
If the prosthesis includes complex features like crossbars and articulating surfaces, then ACL function is replicated, but device complexity increases
Solution Approach 1:
The patent combines multiple stability functions into integrated structures. The crossbar simultaneously provides anterior-posterior stability and rotational control through its articulating surfaces. The flanges are merged with the femoral component to provide both structural support and rotational constraint, reducing the number of separate parts while maintaining comprehensive ACL-like function
Data Source
AI summary
The present disclosure provides knee prostheses that replicate at least a portion of the function of an individual patient's anterior cruciate ligament (ACL). An exemplary knee prosthesis includes a femoral component configured to be implanted on the distal end of the patient's femur and a tibial component configured to be implanted on the proximal end of the patient's tibia. In extension, the femoral component and the tibial component may cooperate to limit anterior movement of the tibial component relative to the femoral component. In flexion, the femoral component may be free to rotate relative to the tibial component.