Acetabular Implant With Localized Hydroxyapatite Coating
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Solution Overview
Problem
Current acetabular implants face challenges in achieving stable osteointegration and reducing bone trauma during screwing, with existing coatings often leading to delamination and increased risk of splinters.
Innovation Solution
The acetabular implant features a screw-type cup with a thick calcium hydroxyapatite coating on convex surfaces and reduced or no coating on screw threads, allowing for improved osteointegration and reduced bone trauma, along with self-tapping cutting threads designed to minimize stress on the acetabular zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick calcium hydroxyapatite coating is applied to the entire cup surface including threads, then osteointegration is improved, but coating delamination and splinter formation increase during screwing
Solution Approach 1:
The patent applies different coating thicknesses to different regions of the cup: a thick coating (100-200 micrometers) on convex portions for osteointegration, and a thin or no coating on thread reliefs to prevent delamination and splintering during screwing. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Ease of operation
If screwing means are introduced into acetabular bone, then primary securing is achieved, but bone traumatism increases
Solution Approach 1:
The patent designs the thread geometry to convert the potentially harmful screwing action into a beneficial compression effect. The threads are configured to compress the sponge-like bone during insertion, transforming the mechanical stress into a beneficial stimulus for bone healing and integration.
Solution Approach 2:
The patent modifies the thread parameters (pitch, angle, depth) to reduce bone traumatism. By optimizing these geometric parameters, the screwing action becomes less invasive while maintaining effective primary securing of the cup in the acetabulum.
3Strength
If coating is applied to thread reliefs, then mechanical engagement is improved, but shearing strength decreases and delamination risk increases
Solution Approach 1:
The patent applies a thin or no coating to thread reliefs compared to the thick coating on convex portions. This local quality differentiation maintains sufficient mechanical engagement while preserving the shearing strength and adhesion of the coating in regions subject to high shear stresses during screwing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances primary and secondary securing, reduces bone trauma, and minimizes the risk of coating delamination, while maintaining excellent mechanical engagement and osteointegration, leading to prolonged implant stability and reduced risk of splinters.
Implementation Method 1
the cup carrying a coating which facilitates osteointegration, such as, in particular, a selective calcium hydroxyapatite coating
Implementation Method 2
the coating is of the thick type on the convex portions of the outer surface of the cup, including in the zones or troughs or recesses of threads that are left free in the screwing means, whilst that coating has a lesser thickness, or is even absent, on the screw reliefs or threads
Data Source
AI summary
A cotyloid implant including a screwable cup receiving an articular insert. The cup is provided with screwing elements (11) on the periphery thereof and more particularly in the equatorial area (2) thereof, the elements being used to penetrate the bone material of the acetabular cup during screwing. The cup includes an osteointegration-facilitating coating such as a selective calcium hydroxyapatite coating. The coating (16) is a thick coating on the convex parts of the outer surface of the cup, including areas or valleys or hollow thread elements which are left free in the screwing elements. The coating is not as thick (17) on raised areas or screw thread areas.