Steven Twork

In certain types of reusable medical devices, inadequate reprocessing between patients can result in the retention of soil or blood, tissue, and other biological debris, according to FDA. Such debris can allow microbes to survive the disinfection or sterilization process, leading to hospital-acquire infections (HAIs) and other adverse patient outcomes.

FDA also notes that reducing the risk of exposure to improperly reprocessed medical devices is a shared responsibility of the agency, healthcare facilities, and manufacturers. For their part, manufacturers are responsible for providing “adequate instructions that are user friendly and proven to work.”¹

A variety of orthopedic and surgical tools, such as the retractor shown in Figure 1, are examples of medical devices that undergo reprocessing between patients. Integrated into such tools is a canted coil spring manufactured by Bal Seal Engineering Inc. that is used to perform latching, locking, and holding functions. As a component in such instruments, the spring must be easy to clean according to medical device industry standards and FDA regulations.

This article presents two methods for cleaning orthopedic surgical instruments containing canted coil springs and other complex components. Developed by Bal Seal, the first method was conducted according to industry standards and FDA requirements. The second method was developed by Symmetry Medical Inc., a manufacturer of orthopedic implants and surgical instruments, for cleaning and reprocessing its reusable orthopedic products, some of which contain canted coil springs. The protocols for both methods had to be verified and validated before use.

Bal Seal Cleaning Method

Bal Seal’s cleaning protocol was validated by a third-party testing house in order to demonstrate that organisms and other soil components can be removed from devices containing canted coil springs using a manual cleaning method. Conducted under worst-case conditions, the test validated that devices containing a canted coil spring can also be properly cleaned using an automated cleaning method.

The test involved common orthopedic devices consisting of a single housing with multiple groove configurations. Each groove was fitted with a BSE 100–series canted coil spring, as shown in Figure 2. The cleaning validation was performed in accordance with the AAMI TIR30:2011 guidance document titled “A Compendium of Processes, Materials, Test Methods, and Acceptance Criteria for Cleaning Reusable Medical Devices.”²

First, the devices were contaminated with defibrinated blood. The residuals tested included hemoglobin and protein. To perform the manual cleaning method, the devices were fully immersed in prepared blood soil and remained in contact with it for a minimum of 15 minutes. After this 15-minute interval, the devices were removed from the blood soil and allowed to dry uncovered at room temperature for a minimum of one hour.

Each device was then rinsed using a water-jet pistol filled with cool tap water at approximately 40 psi. During rinsing, a soft bristle brush and a pipe cleaner were used to thoroughly scrub the devices to ensure removal of gross contamination. Next, each device was immersed in lukewarm tap water containing 1 oz/gal of an enzymatic detergent such as Enzol and allowed to soak for a minimum of one minute. After soaking, the devices were brushed with an appropriately sized pipe cleaner beneath the surface of the prepared detergent for a minimum of one minute. They were then rinsed with the water-jet pistol to remove the residue.

After the devices were free of debris and detergent residue, they were dried with a clean, soft, lint-free cloth and/or a filter pressurized at ≤20 psi. Flushing and full-immersion manual shaking were used to extract fluid, which was tested to determine the levels of hemoglobin and protein remaining on the devices. Sterile water was used for irrigation.

Two tests—the hemoglobin test and the Micro BCA protein assay test—were conducted to determine whether the devices were cleaned sufficiently. For the hemoglobin test, the limit of detection (LOD) was calculated to be 0.16 µg/mL. This value was used in the calculations for test devices with results below the detection limit. The limit of quantitation (LOQ) for this method was calculated to be 0.5 µg/mL. In cases in which the µg/mL value was between the LOD and LOQ, the calculated results were estimated. The hemoglobin concentrations shown in Table I represent the average of the three replicates.

For the Micro BCA protein assay test, the LOD for the assay was calculated to be 1.1 µg/mL. This value was used in the calculations for the test devices for which the absorbance was below the detection limit. The LOQ for the assay was calculated to be 2 µg/mL. In cases in which the µg/mL value was between the LOD and the LOQ, the calculated results were estimated, as presented in Table II.

In order for the test analysis to be considered valid, acceptance criteria had to be met or sufficiently justified. The acceptance criteria were defined as a positive titer on the device being tested to produce a desired log10 reduction in contamination. However, because soil and organisms were incompatible with some of the medical device materials (for example, they did not adhere to the materials or the materials were susceptible to antimicrobial agents), some devices had to be recontaminated with higher titer concentrations or undergo special recontamination methods.

Following the cleaning procedure, no soil was seen during visual inspection on the processed test devices under normal lighting conditions. Thus, it was concluded that the cleaning procedure was sufficient for removing organisms and other soil components from orthopedic surgical instruments.

Symmetry Medical Cleaning Method

Symmetry Medical has issued its own instructions for cleaning reusable surgical instruments, including devices that may contain one or more canted coil springs. According to “Recommended Care, Cleaning, and Sterilization for Reusable Instruments, Instructions for Use,” all Symmetry Medical instruments may be safely and effectively reprocessed using the manual or combination manual/automated cleaning instructions provided in the document “unless otherwise noted in instructions accompanying a specific instrument.”³

The company’s instructions are written in accordance with ISO 17664, “Sterilization of Medical Devices—Information to Be Provided by the Manufacturer for the Processing of Resterilizable Medical Devices.”⁴ This standard sets out the specific information that medical device manufacturers must provide “on the processing of medical devices claimed to be resterilizable, and medical devices intended to be sterilized by the processor.” It defines the types of information required to ensure that a medical device can be processed safely so that it will continue to meet its performance specification.

Symmetry’s reprocessing instructions have been validated as being able to prepare the company’s reusable instruments for use. Its document provides specific warnings, precautions, and processing limitations, along with thorough cleaning instructions. While detailing those caveats is beyond the scope of this article, it is imperative that users read and understand them prior to implementing this cleaning process. All of the company’s protocols must be verified before they are put into practice.

In this method, excess biologic soil is removed from the instruments using a disposable wipe. Devices are then placed in a container of distilled water or covered with damp towels. The company notes that soaking devices in proteolytic enzyme solution facilitates the cleaning process, especially in the case of instruments with such complex features as lumens, mating surfaces, blind holes, and cannulae. Instruments that cannot be soaked or maintained in a damp state should be cleaned within 30 minutes of use to prevent them from drying out before cleaning. This method requires that multicomponent instruments be disassembled before cleaning.

Symmetry’s guide outlines both a manual and a combination manual/automated cleaning process. The manual process involves nine steps, while the combined process involves seven. The test discussed here involved the use of the manual process.

First, the instruments were completely submerged in a proteolytic enzyme solution prepared according to the manufacturer’s instructions, following which they were shaken gently to remove trapped bubbles. Instruments with hinges or moving parts were actuated to ensure that all surfaces contacted the solution. Lumens, blind holes, and cannulations were flushed with a syringe to remove bubbles and to ensure that complete contact was made with the solution. Instruments were soaked for a minimum of 10 minutes. Then, the surfaces were scrubbed using a soft nylon-bristle brush until all visible soil was removed.

Symmetry notes that particular attention should be given to crevices, roughened surfaces, cutting features, hinged joints, sharp edges, box locks, and areas with small components or springs. The company recommends that personnel insert a narrow nylon bristle brush or pipe cleaner into lumens, blind holes, or cannulae with a twisting motion and that they push it in and out multiple times to remove soil. Scrubbing devices below the surface of the enzyme solution minimizes the potential of aerosolizing contaminated solution.

At this stage, the instruments were removed from the enzyme solution, rinsed, and then actuated in tap water for a minimum of one minute. The company recommends that personnel flush lumens, holes, cannulae, and other difficult-to-access areas thoroughly and aggressively. This step applies equally to canted coil springs.

The instruments were then completely submerged in the cleaning solution—an ultrasonic bath containing detergent and de-gas—and shaken gently to remove any trapped bubbles. The lumens, blind holes, and cannulations were flushed with a syringe to remove bubbles and ensure that the solution contacted all the instrument surfaces. Sonic cleaning was performed for a minimum of 10 minutes.

The company recommends that stainless-steel instruments be separated from other metal instruments during the ultrasonic cleaning process to avoid electrolysis. The instructions also note that hinged instruments should be fully opened and that wire-mesh baskets or trays designed for ultrasonic cleaners should be used. Regular monitoring using an ultrasonic activity detector, aluminum foil test, test object surgical instrument, or SonoCheck is also recommended.

After the instruments were removed from the ultrasonic bath, they were rinsed in purified water for a minimum of one minute or until there was no sign of residue detergent or biologic soil. The instructions specify that all moveable and hinged parts should be actuated during the rinsing procedure and that lumens, holes, cannulae, and other hard-to-reach areas such as canted coil springs should be flushed thoroughly and aggressively.

Like the validated Bal Seal method, the Symmetry method specifies that all devices be thoroughly inspected for residual biologic soil or detergent. If contamination is still present, the cleaning process should be repeated. Symmetry requires that its devices be sterilized prior to use and provides specific sterilization instructions at the end of the manual.

Conclusion

Devices containing canted coil springs can be cleaned using methods that meet FDA regulations and industry standards. The tests discussed in this article validated both the Bal Seal and the Symmetry Medical cleaning method and showed that both are suitable for cleaning orthopedic products containing canted coil springs.

References

Steven Twork is the global market manager for medical devices at Foothill Ranch, CA–based Bal Seal Engineering Inc. He has worked in the mechanical sealing and connecting industry for more than 30 years. His areas of expertise include orthopedic instruments, surgical power tools, and implants that use the company’s seal and spring component technology. Reach him at [email protected].