Porous-Lattice Bone Implant Coating for Stable Ingrowth
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Solution Overview
Problem
Existing bone implants with porous structures and calcium phosphate coatings do not effectively utilize the high solubility of calcium phosphate to promote rapid and stable bone ingrowth, as they rely on coatings with high hydroxyapatite content that compromise adhesion.
Innovation Solution
A bone implant with an open-cell porous lattice structure coated with a calcium phosphate layer having a low hydroxyapatite content (<1 wt%) and a high brushite/monetite content (≥90 wt%), extending into the depth of the lattice, is manufactured using 3D printing, ensuring omni-directional coverage and high solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calcium phosphate coating with high hydroxyapatite content is used, then coating adhesion is improved, but bone growth promotion and solubility are reduced
Solution Approach 1:
The invention changes the chemical composition parameters of the calcium phosphate coating by strictly limiting hydroxyapatite content to less than 1 wt% and defining specific ranges for brushite (2-70 wt%) and monetite (2-70 wt%). This parameter modification transforms the coating from a low-solubility, low-adhesion state to a high-solubility, high-bone-growth-promotion state while maintaining adequate adhesion through the controlled composition of brushite and monetite phases.
2Productivity
If coating thickness is increased to enhance bone growth promotion, then bone growth promotion is improved, but the open-cell structure is compromised
Solution Approach 1:
The invention applies different properties to different parts of the implant surface by creating a thin coating layer (5-20 μm) that selectively coats the struts of the open-cell structure without filling the pores. This local application ensures that the coating provides bone growth promotion where needed (on the strut surfaces) while preserving the open-cell architecture and pore connectivity in the interior regions, allowing bone ingrowth channels to remain open.
3Productivity
If coating is applied to extend into pore depths, then bone ingrowth is improved, but coating adhesion is reduced
Solution Approach 1:
The invention utilizes the porous lattice structure of the implant as a template for coating deposition, allowing the coating to conformally coat the internal surfaces of the pores and struts. The porous architecture provides high surface area for coating attachment while the thin coating formulation (5-20 μm) ensures that the coating adheres to the Strut surfaces without detaching during the ingrowth process, maintaining both adhesion and bone ingrowth promotion.
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 facilitates faster and more stable bone ingrowth without compromising long-term effectiveness, as demonstrated by improved osteointegration and osteoconduction, with a thin coating preserving the open-cell structure and promoting bone cell penetration.
Implementation Method 1
By eliminating practically all hydroxyapatite from the calcium phosphate used for the coating, the invention achieves higher solubility
Implementation Method 2
Depending on the material, they can be applied in different ways, for example, by plasma spraying, sputtering, or dipping
Data Source
Figure 1~3
Figure 4a~4b
Figure 5~6b
AI summary
A bone implant with a main body (2) having an open-cell porous lattice structure (3) on its outer surface, formed from a plurality of regularly arranged unit cells (4). The unit cells (4) are designed as a constructed structure and each consists of an interior space (40) and a plurality of interconnected struts (41, 42, 43, 44) surrounding the interior space (40). The porous lattice structure (3) is provided with a bone-growth-promoting coating (5) comprising calcium phosphate. The calcium phosphate coating (5) has a hydroxyapatite content of at most 1% by weight and forms an internal pore coating extending into the depth of the porous lattice structure (3). The invention thus provides a special variant of the coating and departs from the previously prevailing concept of a relatively easy-to-apply and well-adhering coating on the surface of the implant.