Knee Revision Prosthesis with Progressive Rotational Constraint
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Prior revision knee prostheses fail to provide the optimal balance of constraint during knee flexion and extension, often offering either excessive constraint in full extension or undesirable laxity during flexion, which does not accurately mimic the natural knee's articulation path.
Innovation Solution
A revision knee prosthesis design featuring a femoral component with a guide box and a tibial component with a central post that provides progressively decreasing rotational constraint in the coronal and transverse planes as the knee flexes from full extension to flexion, and progressively increasing constraint as it returns to full extension, allowing for more natural movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a revision knee prosthesis provides high rotational constraint in full extension, then stability during standing and weight-bearing is improved, but it causes excessive restriction and unnatural movement during knee flexion
Solution Approach 1:
The guide box and central post are designed with asymmetric geometry that dynamically adjusts the degree of rotational constraint based on knee flexion angle. In full extension, the post engages the narrower anterior portion of the guide box for high constraint, while in flexion, the post moves to the wider posterior portion allowing increased rotational freedom. This dynamic adaptation resolves the contradiction between extension stability and flexion mobility.
Solution Approach 2:
Different regions of the guide box provide different levels of rotational constraint. The anterior region (narrower width) provides high constraint for extension stability, while the posterior region (wider width) provides lower constraint for natural flexion movement. This spatial variation in constraint quality allows the prosthesis to simultaneously achieve both extension stability and flexion mobility.
2Ease of operation
If a revision knee prosthesis provides low rotational constraint during flexion, then natural knee articulation is mimicked, but it causes instability and excessive laxity in full extension
Solution Approach 1:
The asymmetric guide box geometry creates a dynamic constraint system where the degree of rotational freedom automatically varies with knee position. During flexion, the post engages the wider posterior region providing natural articulation, while in extension, the post moves to the narrower anterior region providing enhanced stability. This dynamic behavior resolves the contradiction between flexion mobility and extension stability.
3Ease of manufacture
If a revision knee prosthesis uses symmetric constraint geometry, then manufacturing is simplified, but it fails to provide the optimal balance of constraint during different phases of knee motion
Solution Approach 1:
The guide box is designed with asymmetric width variation along its length, being narrower in the anterior region and wider in the posterior region. This asymmetric geometry is specifically engineered to provide different levels of rotational constraint appropriate for different knee positions, achieving optimal constraint balance during the gait cycle while remaining manufacturable using standard machining processes.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A knee revision prosthesis that provides decreasing valgus-varus and medial- lateral restraint as the knee rotates from extension to flexion, and then increasing restraint as the knee rotates from flexion to full extension. The prosthesis includes a femoral component and a tibial component. The femoral component includes a guide box fixed to the femoral mounting surfaces intermediate the condyles. The tibial component includes a central post fixed intermediate the tibial concavities, which articulates within the guide box and constrains rotational movement of the femoral and tibial components relative to one another in the coronal plane and transverse planes. The post and guide box are constructed and arranged to provide progressively decreasing and then progressively increasing rotational constraint of the femoral component in the coronal and transverse planes as the femoral component rotates in the sagittal plane between full extension to a position in flexion, and then back to full flexion, respectively.