Figure 1. Critical cleaning is essential to achieve osseointegration. Photo courtesy of Dr. Hessam Nowzari, Herman Ostrow School of Dentistry, University of Southern California.
Figure 1. Critical cleaning is essential to achieve osseointegration. Photo courtesy of Dr. Hessam Nowzari, Herman Ostrow School of Dentistry, University of Southern California.

Finding new, expanded applications for our manufacturing capabilities is a key to success. As we live longer, more active lives, the demand for medical devices increases. We have seen growing interest on the part of metal finishers in providing components for medical devices. Cleanliness, contamination control, and surface quality are paramount. Even if you do not do the final device assembly, understanding the goals and requirements and using well-defined, effective cleaning processes goes a long way to increasing the value of your product to current and potential customers.

Medical devices can be implanted (stents, valves, teeth, defibrillators) or they may come in contact with body fluids (endoscopes, surgical instruments, dialysis equipment). If they are implanted, they have to last for a long time, sometimes decades, in a harsh environment that includes high humidity and elevated temperatures. In the case of, say, an implantable tooth (see Figure 1), the device has to favorably interact with the bone. In the medical community, this is referred to as osseointegration. This favorable interaction relates not only to materials of construction but also to cleanliness, surface quality, and surface characteristics.

Given these exacting requirements, critical cleaning is becoming increasingly important. Medical device manufacturers are becoming more and more concerned about the sources of the components that go into their final device. Rather than simply reel off a laundry list of standards, let’s go through some important factors that device assemblers need to consider in working with their supply chain. Appreciating these factors will help make you more valuable to your customer, the final assembler.

A well-defined, consistent cleaning process can greatly assist your customer. An effective cleaning process means one that removes the soils of interest, does not damage the product, leaves the surface in the appropriate condition, and minimizes leachable residue. (We will explain more about leachable residue a bit later.) You also have to think about sources of contamination and about keeping the product clean.

At one time, many medical device manufacturers considered sterilization or disinfection to be the epitome of cleaning. With due respect to Louis Pasteur, manufacturers have come to realize that cleaning itself, the physical removal of soil (matter out of place, both dead and alive) is important to the proper functioning of the device and can potentially impact sterilization efforts as well.

We suggest you define the cleaning process, write it down, and let your customer know your role in critical cleaning. People used to equate critical cleaning or precision cleaning with processes conducted by white-garbed individuals working in a cleanroom. We now know that the critical cleaning process may happen early on in assembly. Prompt removal of metalworking fluids after machining might save your customers headaches during final device assembly.

We want to minimize leachable residue on medical devices. Leachable residue is soil (matter out of place) that comes off of the medical device and interacts with the patient (often referred to as the host or the device recipient). Leachable residue could be a solid, liquid, or gas; and it may be present at very low levels. Achieving zero residue is impossible, even though we may all wish for it.

It is a given that, as a manufacturer, you have to meet or exceed environmental and worker safety requirements. However, even a very benign chemical, one that has a favorable worker exposure profile—and that is very safe for the environment—has the potential for undesirable, even catastrophic, effects on the patient.

Obviously, we have to use chemicals in manufacturing. You can provide added value with prompt, effective soil removal, thorough rinsing, and effective drying. Delaying the cleaning process, or deferring cleaning to your customer is undesirable, because if soil is not removed promptly, it can become adherent. Your customer, the device manufacturer, has to weigh the risks and the benefits of all manufacturing processes. As part of cleaning process validation, the device manufacturer also has to demonstrate that leachable residue has been removed to a level where the benefits to the patient outweigh the risks. Some of these demonstrations include toxicological assessments, both laboratory and paper, as well as analytical laboratory testing.

You may not be directly involved in demonstrating the level of leachable residue related to your cleaning process. However, assuming that you do not have to worry about cleaning, tossing the problem over the fence to your customer, is probably not the best way to expand your business. In contrast, communicating to your potential customer your thoughtful, defined critical cleaning efforts can be an effective approach to demonstrating your value as a supplier.

Cleaning process consistency is a must. Consistency involves avoiding unanticipated changes. This means selecting an optimal cleaning agent, quality cleaning equipment, and achieving a rugged process. We all want to save money. However, the least expensive cleaning products may not be the way to go. Should you use a household laundry detergent from the big box store? Not so much. It is difficult to have a consistent process if “new and improved” appears on the label every few months. Instead, select reliable suppliers of cleaning agents and cleaning equipment who are involved in high value-product and explain the applications for your product. With chemicals, certifications can be helpful in avoiding unexpected surprises.

However, you also have to be alert to other changes. As part of a supply chain, your supplier of metal may change the way the metal is rolled or stamped or cleaned. This can affect the process performance during your fabrication step. Selecting metalworking fluids based on cost alone, and changing suppliers each time you order, is not a good idea. If you change the soil, you have to change the cleaning process. You should also be aware that some of the soils are changing, even without your explicit input. Metalworking fluids are being reformulated for environmental reasons, notably to reduce volatile organic compounds (VOCs). This effort, which began in Southern California (what a surprise!), has been embraced nationally by the Independent Lubricants Manufacturing Association (ILMA). The bottom line is that because metalworking fluids are being formulated with less volatile, higher boiling chemicals, there is the potential for more residue to stick to the surface. You might have to adjust the cleaning process. Therefore, you have to be alert to changes from all of your suppliers.

Given the diversity of design, materials, and the potential applications for medical devices, the requirements are many and varied. What the FDA wants to see and what your customer needs can be very device-dependent. Our contributing authors, and we ourselves have outlined a number of requirements in The Handbook for Critical Cleaning, Second Edition[1-4], and they are continually being updated. We often like to refer people to ISO 10997-17 [5], in part because it is a normative standard that indicates productive thought processes for evaluating the potential risks and benefits of processes and of resulting leachable residue.

You may be working with a manufacturer that is developing a new medical device. The way you design your product and the way you supply your product can impact the critical cleaning during final assembly and can impact product quality. If your customer has not spoken with you, you may find it useful to begin the dialogue.
Such dialog can be useful not only with implantable devices but also with reusable devices. Reusable devices may be repeatedly cleaned by hospital personnel; and even small details of your product design can impact cleanability and performance after repeated uses.

If the above discussion makes you worry a bit, fabulous! The medical device community moves forward through the involvement of people who worry, who think, who consider the risks. You might not be a biologist, but as someone in the medical device supply chain, you can begin to think like one.
The medical device community has benefited from applications in other fields, and will continue to benefit. You can build on your strengths. For example, if you are involved in aerospace, aeronautics, or military applications, consider that some of the challenges you have addressed in producing a successful sealed navigation system may be applicable to medical devices. Your success and experience with high-technology, engineered coatings could be invaluable.
Defining the cleaning requirements and setting up reliable, consistent cleaning processes are good first steps. Communication also helps. This means communication with your customers, your suppliers, your potential customers and suppliers.

D. Albert, “Biomedical Applications: Testing Methods for Verifying Medical Device Cleanliness,” Chapter 13, Handbook for Critical Cleaning, Second Edition: Applications, Processes, and Controls, B. Kanegsberg and E. Kanegsberg, ed., CRC Press (2011)

  1. K. Andrascik, “Cleaning Validations Using Extraction Techniques,” Chapter 12, ibid.
  2. J. Broad and D, Smith, “Cleaning Validation of Reusable Medical Devices: An Overview of Issues in Designing, Testing, and Labeling of Reusable Devices,” Chapter 16, ibid.
  3. B. Kanegsberg, “Clean Critically: An Overview of Cleaning Applications,” Chapter 15, ibid.
  4. ISO 10993-17, “Biological evaluation of medical devices – Part 17: Establishment of allowable limits for leachable substances,”

Barbara Kanegsberg (“The Cleaning Lady”), president of BFK Solutions, Pacific Palisades, Calif., is a recognized expert and consultant in critical/industrial cleaning and contamination control. With practical experience encompassing clinical chemistry and aerospace, she effectively helps companies optimize manufacturing cleaning processes, improve yield, resolve regulatory issues, and maintain trouble-free production. Projects include medical devices, engineered coatings, metals, pump repair, and optics. Kanegsberg is a co-editor of the expanded “Handbook For Critical Cleaning, Second Edition” 2011, CRC Press. She is a member of JS3, an interagency military group, and the ASTM medical device Cleanliness Testing Task Force. For more information, please e-mail