Tibial Insert Post Varus Valgus Constraint
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Solution Overview
Problem
Constrained knee replacement systems often introduce biomechanical inefficiencies due to the lack of natural tibiofemoral rotation and varus/valgus constraint, which can lead to improper alignment and increased shear forces on the patella, reducing the longevity of the prosthesis.
Innovation Solution
A tibial insert with a post that provides varus/valgus constraint and permits tibiofemoral rotation, featuring a base and a post with medial and lateral surfaces that engage a femoral component, allowing rotation about a superior-inferior axis over a constrained flexion/extension range, and includes a posterior cam for additional stabilization and rotation promotion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a constrained knee replacement system is used to provide varus/valgus constraint, then stability is improved, but natural tibiofemoral rotation is lost and biomechanical inefficiencies occur
Solution Approach 1:
The constrained surface is segmented into multiple zones with different functional characteristics. The first zone provides varus/valgus constraint while the second zone permits tibiofemoral rotation, allowing the single component to deliver multiple distinct mechanical functions through spatial segmentation of its surface properties.
2Stability of the object's composition
If varus/valgus constraint is provided over the full flexion/extension range, then alignment stability is improved, but quadriceps alignment and patellar tracking are compromised
Solution Approach 1:
Different regions of the constrained surface are assigned different functional qualities. The first zone has high constraint quality for varus/valgus stability, while the second zone has low constraint quality to permit rotation and reduce patellar shear forces. This local differentiation of surface properties allows the prosthesis to provide stability where needed while avoiding harmful effects in other regions.
3Stability of the object's composition
If a constrained tibial insert is used to replace ligament function, then joint stability is improved, but biomechanical efficiency and prosthesis longevity are reduced
Solution Approach 1:
The constrained surface transitions from a static, uniformly constrained design to a dynamic system where constraint is selectively applied. The first zone provides constraint when needed for stability, while the second zone dynamically permits rotation during movement, allowing the prosthesis to adapt its mechanical behavior to physiological requirements and improve longevity.
Data Source
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AI summary
A tibial insert (300) includes a base (301) and a post (302) extending from the base along a longitudinal axis. The post has a medial surface (304), a lateral surface (306), and a height (H) along the longitudinal axis. The medial surface has a medial section (320), and the lateral surface has a lateral section (322) oriented substantially parallel to the medial section. The medial section and the lateral section each have a width (W) in a substantially anterior-posterior direction that is sufficient to enable varus/valgus constraint over a flexion/extension range from extension to about 90 to 120 degrees of flexion when the tibial insert is mated with a femoral component (200).