Multi-material Spinal Implant Composite Structure
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Solution Overview
Problem
Current spinal implants lack optimal osseointegration and design features that effectively promote bone growth and stability, leading to suboptimal integration with the surrounding bone tissue.
Innovation Solution
The development of an implantable device combining a polymeric component with a metallic component, where the metallic component has a substantially solid region and a porous region, mechanically joined to each other, with the polymeric component featuring roughness features on a larger scale than the metallic component, enhancing osseointegration and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-material implant design is used, then the device structure is simple and easy to manufacture, but the osseointegration capability and mechanical strength are insufficient
Solution Approach 1:
The implant combines polymeric material and metallic material into a single device. The polymeric portion provides osseointegration capability with bone-facing surfaces that promote bone ingrowth, while the metallic portion provides structural strength and rigidity. This composite structure resolves the contradiction by integrating materials with complementary properties rather than using a single material that must compromise between strength and biocompatibility.
Solution Approach 2:
Different portions of the implant have different material properties optimized for their specific functions. The polymeric portion with its bone-facing surfaces is optimized for osseointegration and bone contact, while the metallic portion is optimized for providing structural support and mechanical strength. This local differentiation of material quality allows each region to perform its intended function optimally.
2Strength
If a solid metallic structure is used, then the mechanical strength is high, but the osseointegration and bone growth promotion are reduced
Solution Approach 1:
The implant uses a composite structure where the metallic portion provides the necessary mechanical strength and rigidity to support physiological loads, while the polymeric portion with specialized bone-facing surfaces provides osseointegration capability. This division allows the metallic component to be optimized for strength without compromising bone integration, as that function is handled by the polymeric material.
3Reliability
If a polymeric material is used for the entire implant, then the osseointegration is improved, but the mechanical strength and load-bearing capacity are reduced
Solution Approach 1:
The implant combines polymeric material optimized for osseointegration with metallic material optimized for load-bearing. The polymeric portion with bone-facing surfaces promotes bone ingrowth and integration, while the metallic portion provides the structural framework capable of withstanding physiological loads. This composite approach allows both requirements to be satisfied simultaneously.
4Ease of manufacture
If uniform surface roughness is applied to all components, then the manufacturing process is simple, but the osseointegration effectiveness is reduced
Solution Approach 1:
The implant features differentiated surface roughness characteristics in different regions. The polymeric bone-facing surfaces have a first roughness characteristic optimized for promoting bone ingrowth and osseointegration, while the metallic bone-facing surfaces have a second roughness characteristic optimized for their specific function. This local differentiation of surface quality enhances osseointegration effectiveness in each region according to its specific requirements.
Data Source
AI summary
An implantable medical device, such as an intervertebral spacer, may comprise a polymeric component and a metallic component. The metallic component can contain both porous metal and substantially-solid metal. The polymeric material can contain particles of an osseointegrative material. The metallic component can be more protruding toward bone than the polymeric component while having a smaller dimension of roughness than the polymeric component. In embodiments, the pin may press-fit against substantially solid metal. The porous metal may surround solid metal which in turn may surround the pin. The pin may have a press-fit with metal and a looser fit with polymeric component, if the metal components and polymeric components are trapped. A pin may connect superior and inferior metal components by a press-fit. The central opening may be exposed to porous metal and also to substantially-solid metal and to polymer. Specific geometries of implants are disclosed.