Although the Food and Drug Administration (FDA) has reported progress on reducing overall infection rates with enhanced safety measures and better disinfection methods, the risks associated with reusable medical devices are an ongoing challenge, with drug-resistant microbes and other organisms continuing to survive the cleaning process at an unacceptable rate.1

A technician inserts surgical instruments into an autoclave for sterilization. (Credit: iStock)

The reality is that medical device cleaning is a complex undertaking under the best of circumstances, and the risk of human error cannot be entirely eliminated — putting patients at risk. Even when processes are followed precisely, problems can occur. In its ongoing efforts to mitigate infection transmission associated with duodenoscopes, the FDA notes that the problem was found even when manufacturer specifications for cleaning, disinfection, and sterilization had been followed.2

While cleaning instructions, training, and testing with microbiological culturing and identification remain key strategies for reducing infection risk, a growing area of focus is centered on device design.

Cleanability Optimization Starts with Design

The practice of incorporating “cleanability” into medical device design can yield significant benefits. Design features that inhibit or resist the growth of organisms, and designs that make devices easier to clean are key to reducing patient infections — an outcome made all the more urgent by the emergence of antibiotic resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococus (VRSA) and others.3

Medical device cleaning problems are a persistent theme among the equipment research organization ECRI Institute’s annual list of Top 10 Health Technology Hazards.4 As Scott Lucas, the organization’s associate director of accident and forensic investigation explained following release of the 2017 list, the problem is greater than issues with any single device or shortcoming in cleaning processes.5 “This is really a systemic challenge,” Lucas said, adding that the FDA was likely to begin pushing device makers to take cleaning into consideration during the design process.

Design Imperfections Identified Prior to Production

A source of opportunity for improving cleanability design of medical devices has emerged from a lesser known metal finishing process called electropolishing.6

Rivets in an orthopedic medical tray expose a risk that pathogens and other hazardous substances would not be removed in the cleaning process, creating a risk of infection transmission. (Credit: iStock)

In an era of increasing collaboration on infection control between medical device manufacturers and healthcare researchers and providers, electropolishing occupies a unique position as a bridge between design and infection control. This is because electropolishing, a process for improving the surface finish of metal parts, is one of the last steps before medical devices and surgical instruments made of the following materials become available on the market:

  • Implantable alloys.

  • 316L stainless steel.

  • Cobalt chrome.

  • Ti 4L6V (Grade 4 titanium).

  • Nitinol, tantalum (refractory metals).

  • Other alloys used in medical device manufacturing.

  • 17-4 PH, 17-7 PH.

  • 300 series stainless.

  • 400 series stainless.

  • Aluminum, copper, steel, and virtually any alloy.

While electropolishing is used to create an ultraclean and corrosion-resistant finish, a key benefit for medical device manufacturers is the visibility it provides into designs that impair the cleanability of their products, including elements that trap bacteria, water and other liquids, and make devices more susceptible to pathogen growth. This is often discovered when medical device components cannot be pre-cleaned and rinsed in a controlled and repeatable manner.

Finish First methodology results in design changes that optimize device cleanability and make the electropolishing process more effective. (Credit: Able Electropolishing)

Medical device engineers looking for ways to improve cleanability are increasingly adopting a collaborative approach in the R&D and prototyping phase of design, turning to metal finishing and electropolishing experts like Chicago-based Able Electropolishing to leverage the electropolisher’s expertise with metal finishing. This approach, which Able has dubbed its “Finish First” methodology, has resulted in design changes that optimize device cleanability and make the electropolishing process more effective.

It’s an approach with enormous potential for improving patient safety, reducing product recalls, improving time to market and preventing late-stage design changes. Of all the medical devices sent to us for electropolishing — both reusable and non-reusable — approximately half exhibit major cleanability issues because they were not designed with cleanability in mind.

How Electropolishing Works

Electropolishing combines DC power and a blended chemical electrolyte bath to reduce roughness and remove flaws from the surface of metal parts. This includes eliminating burrs and other imperfections where pathogens can hide. Electropolishing also creates a surface where liquid beads off because of a lower coefficient of friction, making it easier to clean and resistant to bacteria growth.

As one of the final steps in the manufacturing process, electropolishing is used by manufacturers of commonly used implantable medical devices because of its ability to create a micro-smooth, corrosion-resistant and oxygen-rich surface that inhibits the growth of bacteria and reduces the risk of inflammatory and allergic reactions in patients.

A nurse washes medical instruments. Common components and design features can negatively affect a medical device’s capacity for effective cleaning and rinsing. (Credit: iStock)

A study on implant-associated infections that lead to serious complications and soft tissue damage found that electropolished titanium and stainless steel had a “significant decrease in the amount of bacteria adhering” to the surface, compared to non-electropolished metal.7 “Hence electropolishing … could be advantageous … in minimizing bacterial adhesion and lowering the rate of infection,” the authors wrote.

Corrosion resistance is also a factor in infection control.8 The “ability of a surface to resist corrosion is of major importance” to hygienic quality as corrosion can “markedly” decrease cleanability, another study notes.

Medical Device Challenges

In addition to surgical implants, electropolishing is used on reusable “critical devices” that penetrate tissue or vascular structures, including surgical instruments, cardiac catheters, and some endoscopes. These include drills, taps, reamers, guide wires, tunneling rods, guides, blades, and scopes.

Other medical devices benefiting from electropolishing include non-tissue penetrating medical devices, also known as “semi-critical devices,” including some endoscopes, laryngoscope blades, and respiratory therapy equipment.

Critical, reusable medical devices require high-level disinfection (HLD) processes that eliminate all microorganisms in or on the device, except for small numbers of bacterial spores. ISO 17664, a standard adopted by the FDA, requires that manufacturers provide processing standards for medical devices that require cleaning followed by disinfection and/or sterilization.

Disposable, single-use medical devices can also benefit from design features that make them easier to sterilize.

Device Design Features that Breed Problems

At Able, for example, electropolishing processes encompass the rinsing of medical devices of all shapes and sizes enabling very precise observations of a part's tendency to trap liquid. The company has worked with numerous medical device OEMs over its 64-year history to suggest design changes that result in an improved surface finish even before electropolishing. Common components and design features that can negatively affect a medical device's capacity for effective cleaning and rinsing include:

  • Metal on metal contact.

  • Rivets.

  • Stamped or folded metal.

  • Blind holes.

  • Small cavities or narrow through holes.

  • Porous metals or coatings.

  • Spot welding, weld slag, and weld scale.

  • Welded components vs. subassemblies able to be broken down.

  • Solid rod vs. tubing.

Medical device cleaning is a complex undertaking under the best of circumstances, and the risk of human error cannot be entirely eliminated. (Credit: iStock)

In addition to creating surface changes that make cleaning more difficult, some features — like folded metal and rivets — can take 24–48 hours for trapped liquid to “bleed” out.

Some best practices suggested by the company's experience include eliminating problematic features whenever possible, but also testing for rinse-ability and drying during the prototyping process, well before medical devices go into production.

For metal components that undergo electropolishing as a final process, the company recommends that manufacturers consult with their electropolishing partner in the design phase. Device manufacturers who take advantage of additional expertise around metal finishing can incorporate small changes that make electropolishing even more effective for improved cleanability, wear and corrosion resistance.

Design for Cleanability Examples

Here are two examples of devices where design features were found to impede cleanability.

Orthopedic Medical Trays. Rivets in an orthopedic medical tray used by a major medical OEM manufacturer were trapping chemicals and bleeding out 24–48 hours later, exposing a risk that pathogens and other hazardous substances would not be removed in the cleaning process, creating a risk of infection transmission. Fortunately, the issue was found during the prototyping phase, and Able's recommendation to replace the rivets with welded corners was implemented. As an additional bonus, lead time was reduced by two days.

Prostate Surgery Devices. A single-use medical device for benign prostate surgery was made with spot welding that created surface discoloration and imperfections where pathogens could be trapped. The manufacturer had specified that the device undergo a complex passivation procedure, but passivation testing revealed the problem. Able recommended design changes that included a continuous weld and the use of electropolishing to alleviate discoloration.

Such examples are the results of an innovative approach to a stubborn problem as a growing number of manufacturers begin to incorporate cleanability into medical device design. A 2016 article describes how Cincinnati-based manufacturer Ethicon and its reprocessing subsidiary Sterilmed began incorporating reprocessing considerations into the design process.9 Able has been providing similar guidance to OEMs since 1954.

Able's “Finish First” methodology provides device manufacturers with recommendations and input gleaned from its processes that can be used to guide R&D, prototyping, and validation of manufacturing processes to ensure that parts are designed for optimal cleanability and performance.

Start at the Finish: A Better Way

The experience of Able, its medical device manufacturing clients, and others illustrates the benefits of applying the lessons learned in a finishing process to create a better process from the start. A coordinated approach that integrates design with best practices for eliminating infection risks can yield benefits that go beyond cleanability to produce design features that inhibit the growth of pathogens in the first place. By leveraging the expertise of every stakeholder in the process, the best possible outcome for patients becomes a matter of design.

References

  1. C. Hale, “FDA reports higher con- tamination rates for reprocessed duodenoscopes ,” Fierce Biotech, 2019: 4.

  2. Infections Associated with Reprocessed Duodenoscopes ”.

  3. H. Chambers, F.R. DeLeo, “Waves of Resistance: Staphylococcus aureus in the Antibiotic Era ," Nat Rev Microbiol. 2009 Sep; 7(9): 629–641.

  4. Top 10 Health Technology Hazards for 2019 ”.

  5. Top 10 Health Technology Hazards for 2017 ".

  6. Apparatus and method for enhancing electropolishing utilizing magnetic fields ”.

  7. L.G. Harris, et al., “Staphylococcus aureus adhesion to standard micro-rough and electropolished implant materials ,” J Mater Sci: Mater Med (2007) 18: 1151.

  8. L.R. Hilberta, et al., “Influence of surface roughness of stainless steel on microbial adhesion and corrosion resistance ,” International Biodeterioration & Bio- degradation 52 (2003) 175–185.

  9. A. Rubenfire, “Improper cleaning may be leading to broken devices, infections ,” Modern Healthcare, November 07, 2016.

This article was written by Thomas Glass, CEO, and Pat Hayes, Vice President, Business Development, Able Electropolishing, Chicago, IL. For more information, click here .


Medical Design Briefs Magazine

This article first appeared in the October, 2019 issue of Medical Design Briefs Magazine.

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