Tibial Implant Fixation Feature Sizing for Bone Ingrowth
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Solution Overview
Problem
Traditional fixation features for tibial implants in knee arthroplasty procedures often fail to match the metaphyseal recesses of the tibia accurately, leading to reduced bone ingrowth and increased sensitivity to implant micro-motion due to premature contact between fixation features and recess surfaces.
Innovation Solution
The method involves determining the appropriate size of the distal fixation feature and forming metaphyseal recesses in the tibia to create a gap between the fixation features and recess surfaces, ensuring the tibial implant seats correctly on the resected surface, with the recesses sized to exceed the fixation feature dimensions to maintain a gap even at maximum tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixation features (stem, keel, fins) are used for tibial implant placement, then the implant can be secured to the bone stock, but the fixation features contact the metaphyseal recess surfaces before the distal surface seats, reducing bone ingrowth capability
Solution Approach 1:
The patent applies parameter changes by modifying the sizing relationship between fixation features and metaphyseal recesses. Specifically, the fixation features are designed to be smaller than the metaphyseal recess dimensions, creating a size differential that prevents premature contact. This parameter adjustment ensures proper seating sequence while maintaining secure fixation and maximizing bone ingrowth surface area.
2Strength
If fixation features are sized to match metaphyseal recesses closely, then secure fixation is achieved, but the distal surface cannot properly seat on the resected proximal surface
Solution Approach 1:
The patent applies local quality by differentiating the dimensional relationships between different components of the implant system. The fixation features are locally sized to be smaller than their corresponding metaphyseal recesses, while the distal surface is sized to match the resected proximal surface dimensions. This localized dimensional differentiation ensures both proper seating and secure fixation simultaneously.
3Quantity of substance
If the metaphyseal recesses are sized to exactly match fixation features, then complete filling is achieved, but bone ingrowth surface area is reduced
Solution Approach 1:
The patent applies partial action by intentionally leaving the metaphyseal recesses partially unfilled relative to the fixation features. The fixation features are sized to occupy only a portion of the available metaphyseal recess volume, deliberately creating gaps that preserve bone ingrowth surface area while still achieving adequate mechanical fixation through the porous material.
Data Source
AI summary
Methods, techniques and apparatuses are disclosed including exemplary methods of performing a knee arthroplasty of the tibia. One exemplary method can include determining at least a depth of a distal fixation feature of a tibial implant, and forming a metaphyseal recess in a proximal portion of the tibia. The recess can be configured to receive the distal fixation feature therein and can be sized to exceed at least the depth of the distal fixation feature such that when a distal surface of the tibial implant contacts a proximal surface of the proximal portion of the tibia and the distal fixation feature is received in the metaphyseal recess, a gap remains between the distal fixation feature and one or more surfaces that form a portion of the metaphyseal recess.