Tibial Baseplate Curved Bone Interface for Knee Arthroplasty
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Solution Overview
Problem
Current tibial baseplate designs in knee arthroplasty suffer from loosening due to inadequate bone interface loading and inaccuracies in bone preparation, leading to rocking and instability, particularly because the bone contacting surface remains planar and simple.
Innovation Solution
The design incorporates a tibial baseplate with a bone interface surface featuring convexities and curves that are tangent to specific planes, enhancing the surface contact area and resistance to loading, along with specialized instrumentation for preparing non-planar bone resections using curved cutting guides and sawblades to match the implant geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tibial baseplate bone contacting surface is kept planar, then the instrumentation and manufacturing process is simple, but the resistance to tibial bone interface loading is insufficient leading to loosening
Solution Approach 1:
The patent applies curvature to the bone contacting surface of the tibial baseplate by introducing convexities with defined radii of curvature. The bone contacting surface includes at least one convexity having a radius of curvature between 5mm and 20mm, which increases the surface area and improves load distribution to the tibial bone, thereby enhancing resistance to loosening while maintaining manufacturability through standardized curved geometries.
2Reliability
If the bone contacting surface is made non-planar with convexities, then the resistance to loading increases, but the accuracy of bone preparation becomes more critical
Solution Approach 1:
The patent incorporates preliminary action by designing the bone contacting surface with convexities that compensate for potential preparation inaccuracies. The convexities create a more tolerant interface that can accommodate variations in bone preparation accuracy, ensuring stable load transfer and reducing the risk of loosening even when perfect planarity is not achieved during surgery.
3Strength
If the articular surface has concavity and the bone interface surface has convexity, then the load transfer characteristics are improved, but the instrumentation complexity increases
Solution Approach 1:
The patent applies local quality by differentiating the geometry of different surfaces of the implant. The articular surface has concavity to match the femoral component and improve articulation, while the bone contacting surface has convexity to improve load distribution to the bone. Each surface is optimized independently for its specific function, allowing improved load transfer characteristics without requiring the entire implant structure to be overly complex.
Data Source
AI summary
A prosthetic implant comprises an articular surface and a bone contacting surface. The articular surface has a first concavity extending along a first curved axis and the bone contacting surface has a convexity extending along a second curved axis. Geometric relationships between the concavity of the articular surface and convexity of the bone contacting surface are described. A resulting feature of this implant is a bone contacting surface including both planar and non-planar geometries. Instrumentation and a method for the preparation of the non-planar bone surface are also described.