Indexable Tibial Insert Rotation for Knee Prosthesis Alignment
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Solution Overview
Problem
Constrained tibiofemoral articulation in knee joint prostheses can lead to undesirable higher stresses at the bone/implant interface due to independent alignment of femoral and tibial components during surgery, resulting in suboptimal alignment and potential instability.
Innovation Solution
A tibial prosthesis assembly with a tibial insert that includes a superiorly extending stabilizing post and a locking mechanism allowing for a predetermined amount of rotation relative to the tibial component, enabling indexable mating at multiple fixed rotational orientations, thereby optimizing alignment and reducing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tibial insert is fixed relative to the tibial component with constrained articulation, then the tibiofemoral joint stability is improved, but the stress at the bone/implant interface increases due to independent alignment of femoral and tibial components
Solution Approach 1:
The patent transforms the static fixed connection between tibial insert and tibial component into a dynamic adjustable connection. The indexing mechanism allows the tibial insert to rotate to different angular positions (e.g., 0°, 15°, 30°) relative to the tibial component, enabling optimization of alignment between independently positioned femoral and tibial components while maintaining joint stability
Solution Approach 2:
The patent changes the rotational parameter of the tibial insert relative to the tibial component. By providing multiple fixed rotational orientations through indexing features (such as indexed holes, splines, or cam mechanisms), the system allows selection of optimal alignment parameters to reduce stress at the bone/implant interface while preserving joint stability
2Manufacturing precision
If the tibial insert is allowed to rotate freely, then the alignment between femoral and tibial components can be optimized, but the joint stability is compromised due to excessive movement
Solution Approach 1:
The patent implements a semi-dynamic system where the tibial insert can rotate during installation and adjustment, then locks into fixed positions. This provides the benefits of adjustable alignment while preventing excessive movement during use, maintaining joint stability
Solution Approach 2:
The patent divides the rotational movement into discrete segmented positions using indexing features. Instead of continuous rotation, the tibial insert is constrained to specific angular positions (e.g., every 15° or 30°), providing precise alignment options while limiting movement to maintain stability
Data Source
AI summary
A tibial prosthesis assembly including a tibial component and a tibial insert. The tibial component includes an inferior bone engaging surface, a superior surface, and a first retention feature. The tibial insert includes an inferior tibial component engaging surface, a superior bearing surface, and a second retaining feature. The first and the second retaining features cooperate to mate the tibial insert with the tibial component at one of a plurality of fixed rotational orientations relative to the tibial component.