Ole Zoffmann Andersen

Standard coatings and surface modification technologies for the orthopedic market have been used for decades. Nevertheless, medtech companies continue to look for ways to improve the osseointegration process – and breakthrough advances are on the horizon. Elos Medtech has developed a new coating and surface technology for OEM’s to supply state-of-the-art implants with optimal properties for osseointegration.

Coating and surface modifications for the orthopedic market

Today, there is a wide range of applications for coating and surface modifications for the orthopedic market. The products are focusing on improving wear resistance and osseointegration. Plasma-sprayed titanium surfaces or calcium phosphate/hydroxyapatite (HA)-based coatings are currently the standard methods for within-the-bone implants. However, these methods are associated with issues concerning coating delamination.

Surface modifications to minimize coating delamination in orthopedic implants

Let us shift focus to the dental industry for a minute. While the orthopedic industry is fairly conservative when it comes to introducing new surface technologies for improving osseointegration, there may be much to learn from the field of dental implant research.

For example, numerous surface modifications based on processes as diverse as the grit blasting, anodization, and chemical surface modifications are currently used in the dental industry to enhance osseointegration. While many of these processes still pose challenges when it comes to bacterial infections, the risk of coating delamination is low or nonexistent, compared to, for example, HA-based coatings.

Surface roughness to minimize bacterial infection in orthopedic patients

With bacterial infections being of high concern, a key consideration is the porosity and texture of the surface coating. Research shows that rough surfaces facilitate bacterial adhesion, making it more difficult to treat these infections with systemic antibiotics.

On the other hand, roughness in the micrometer range is beneficial for stimulating osteogenesis and, thus, ensure fixation of the implant in the bone. Considering these factors, a turned surface with a roughness in the nanometer range would be desirable for reducing the risk for bacterial infections. This, however, requires that other means than micrometer roughness, for stimulating osteogenesis, are introduced.

A new coating and surface technology to meet market needs

Based on previous experiences with thick hydroxyapatite coatings, some OEMs might fear coating delamination. This risk, however, is greatly reduced by tailoring the substrate adhesion and keeping the correct thickness of the applied coating to a minimum.

Elos Medtech has, through an international collaboration, developed a new coating and surface technology that accelerates the process of osseointegration for implants with smooth surfaces. In collaboration with iNANO at Aarhus University, Danish Technological Institute, Medical University of Innsbruck and the Innovation Fund Denmark, a titanium oxide-based PVD coating, that releases small amounts of the bone-stimulating element strontium, has been developed. This release does not compromise the stability of the coating and therefore the integrity of the deposited structure is maintained throughout the lifetime of the implant. Adhesion is ensured by including a graded binding layer, matching the chemistry of the substrate material, and applying a very thin coating in the one to two micrometer range.

Our new surface technology does not only minimize the risk of coating delamination and bacterial infection – we have benchmarked this technology against leading dental implant surfaces and it outperforms these surfaces for early-stage peri-implant bone volume. In other words, implants modified with our technology are rapidly integrated into the bone and have a larger peri-implant bone volume to support the stresses on the implant. Thus, OEMs are able to supply state-of-the-art implants with optimal properties for osseointegration, leading to faster rehabilitation of the patient.

Do you want to learn more? Also, read:

• Measurement and Surface Analysis of Medical Devices
• Surface Analysis Techniques for Medical Technology Devices

For requests – whether they be technical or timeline based – visit Elos Medtech. We help you from design to prototyping through to compliance and global distribution.

In my latest blog article Surface analysis techniques for medical technology devices, I told you that we recently invested heavily in advanced surface analysis equipment. In this article I am getting a bit more into the details about what we actually can measure with our new equipment.

A scanning electron microscope for advanced analytical applications

Our new Scanning Electron Microscope (SEM) is equipped with various features. It can produce high-resolution images of surface structures, and has a very high magnification range of up to 60,000X. It can perform relative quantification of a material’s elemental composition and is also able to image polymer surfaces.

Information on material composition and topography

The microscope is equipped with two types of electron detectors; one that detects backscattered electrons (BEI) and one that detects secondary electrons (SEI). Common to both of these modes of detection is that the resulting image is generated from the intensity of the signal reaching the detector. The grayscale image represents the electron count of the detector resulting from a specific position of the electron beam on the sample surface. As a result, dark areas represent a relatively lower electron count compared to brighter areas.

Using the BEI detector, the resulting image contains a high degree of information on the material composition as more electrons are backscattered from heavier atoms at the surface compared to the amount reflected from lighter elements. The SEI detector provides images with a high degree of topographical information. This is a result of the depth, within the samples, at which these  electrons are emitted. Also, the SEI detector is better suited for obtaining high quality images at larger magnification.

Low vacuum mode enables imaging of polymers

Due to the nature of the electron microscope, high quality images require good electrical conductance of the material being examined. This can cause some difficulties when imaging for example polymeric materials as negative charge, building up on the surface of the material, will deflect the incoming electrons used for imaging. For such materials the microscope is equipped with a low vacuum mode. Running the microscope in this mode introduces charge carriers in the form molecules from the ambient air. This reduces the degree of sample charging and enables the imaging of poorly conducting materials, such as polymers.

Using the SEM for determining chemical composition

Elemental analysis, using the SEM, is based on the detection of characteristic X-rays. These are generated by the interactions between the incident electrons, and the electrons of the atoms comprising the sample. The majority of the collision events, that generate such X-rays, take place below the surface of the material. As a result, the probing depth of the Energy Dispersive X-Ray Spectroscopy System (EDX) is typically a few micrometres. One of the factors affecting the probing depth is the acceleration voltage used for the analysis.

The analysis is performed by scanning the electron beam over the area of interest, while collecting the complete X-ray spectrum. From the collected spectrum, the chemical composition can be calculated. The method is semi-quantitative, as the elemental composition is expressed as a function of the total number of elements included in the analysis. When generating characteristic X-rays, the acceleration voltage of the incoming electrons, is highly important. Some elements can be detected using a relatively low acceleration voltage, while detection of others requires a higher voltage.

Our new microscope is capable of operating with three different acceleration voltages. This enables detection of a wide range of elements, including carbon, titanium, vanadium, aluminium, chromium, cobalt and tungsten. As a result, the EDX system can e.g. be used for distinguishing between grade 4 and grade 5 titanium. Another option with the EDX system is to perform elemental mapping of surface features, resulting in an overview of the spatial location of elements.

Specialised optical microscope enables measurement of surface roughness parameters

Our white light interference surface profiler is a specialised optical microscope that uses optical interference to detect the focal point on the surface of a sample. Using piezoelectronics the height position of the microscope lens can be varied with a high degree of precision, in steps of around 10 nanometres. By continuously varying the height position of the lens, while detecting the interference pattern resulting from the surface, the focal point can be determined for each position of the area being imaged. This results in a 3D topographical map of the surface. Via the equipment software, the acquired data can be treated to allow for calculating both classical 2D surface roughness parameters as well as 3D parameters.

The size of the analysed area depends on the objective lens used for the analysis. The lens also determines the resolution of the acquired 3D data set. Larger surface roughness values can be determined using an objective lens with low magnification. Lower surface roughness values require an objective lens with a higher magnification.

X-Ray fluorescence for fast and reliable identification of materials

While our SEM/EDX system is capable of determining material compositions, this approach is relatively time consuming and sets certain limits to the size of the sample being analysed. Our new X-Ray Fluorescence analyser (XRF) is also capable of determining the elemental composition of metals but does this under ambient conditions and is, furthermore, not limited by the size of the sample being analysed. The XRF analyser utilizes the principle of X-ray fluorescence. When radiating a sample with X-rays, the sample atoms will generate characteristic X-ray emission. Similar to the EDX analysis of the SEM, the emission can be used qualitatively to both determine and quantify the elements of the material. The penetration depth of the incident X-rays is significantly larger than for the electrons used by the SEM/EDX. As a result, the XRF analysis determines the bulk composition of the material and is, thus, better suited for e.g. verifying that the correct material is being used for the production of a specific part.

Every aspect of our manufacturing process, from design to distribution, must meet strict quality standards. Not only our customers, but also vendors, suppliers, contractors, OEMs and third parties need to be sure that their products comply with medical device rules and regulations. With our new surface and material analysis equipment, we can find and minimise possible risks in the manufacturing process. We can improve and refine processes, contributing to our state-of-the-art production facilities, and ensure that we meet these strict quality standards. Having this equipment in-house, we can measure more often and with greater accuracy than before. It provides a higher product quality, and minimises the risk that a product that doesn’t meet the quality standards, is delivered to the customer.

Did you find this article interesting? Let me know by sharing it on LinkedIn! There you can find more updates and news from the medtech industry and Elos Medtech. Also read Surface analysis techniques for medical technology devices.

Do you produce medical devices that require specific standards? The modern field of medical device manufacturing requires state-of-the-art production facilities, capable of producing units with very small tolerances. For medical devices that are intended for use in the human body, it is crucial to find and minimise possible risks in the manufacturing process. In addition to the equipment that we have access to via our extensive network in the scientific community, we recently invested heavily in advanced surface analysis equipment to ensure the highest production standards, and meet our customers’ demands.

Surface analysis techniques for products that require specific standards

Possible risks during manufacturing may involve the use of wrong materials in the preparation of units, sources of contamination or issues relating to surface finish. We manufacture several products that require specific standards. With respect to surface roughness, some of our customers have very specific requirements. Often, it is difficult to analyse the surface roughness, especially on surfaces that have curvatures in two directions. Using our new 3D optical surface profiler, we are able to perform fast and reliable, non-contact, analysis to determine various surface roughness parameters. Additionally, the technique allows for assessing the 3D structure of, for example, surface defects.

Characterization of surface structure and chemical composition of a surface

With our new Scanning Electron Microscope and Energy Dispersive X-Ray system (SEM/EDX), we can easily perform detailed characterization of surface structure at magnifications of up to 60.000x and also determine the chemical composition of a surface, or features found at the surface. As a result, we can make sure the product meets our customers’ specific requirements. The equipment is also used to identify root causes when challenges are encountered in the production, for example if surface contaminations would be found.

We draw conclusions based on facts and make improvements accordingly

Our new surface analysis equipment enables us to perform analysis and draw conclusions based on facts. This saves us a lot of time in terms of production related issues. By utilising our systems for performing, for example chemical analysis, we can quickly pinpoint the production step that is likely to be the root causes of a specific issue.

We meet the production requirements on a day-to-day basis

The surface analytical techniques are utilised on a day-to-day basis to verify that we meet the production requirements. Moreover, root causes analysis in relation to production challenges are also performed. These root cause analysis are used to prevent the reoccurrence of specific challenges. This all adds up to the purpose of our investment – to meet our customers’ specific requirements.

Would you like to know more about our new surface analyses equipment? Perhaps get into the details a bit more? Keep an eye out for our next blog article! Until then, do not hesitate to contact us with any questions. Also visit Elos Medtech’s website to read more about our manufacturing process.