Simulation of reprocessing cycles: end-of-life tests, lifecycle tests, aging of reusable medical devices

Reusable medical devices undergo repeated mechanical, chemical, and thermal stress during clinical use and reprocessing. Reprocessing cycle simulation replicates these real-world stresses in a controlled manner through standardized testing. This allows for the evaluation of a product’s service life and performance under real-world conditions. Simulation replicates the stresses caused by reprocessing in a controlled manner in order to test the service life of reusable medical devices. The goal is to systematically investigate the effects of reprocessing over the intended service life. End-of-life tests thus provide an essential basis for evaluating the durability of materials, functional safety, and long-term performance of reusable medical devices. This blog post describes the methodological and regulatory framework for these tests in the context of reprocessing validation and product development.

As part of their intended use, manufacturers of resuable medical devices are required to specify the product's intended service life. While EU Regulation 2017/745 (MDR) does not explicitly define the term “service life,” it sets forth basic safety and performance requirements in Annex I from which this obligation can be indirectly derived. According to Annex I, Chapter I, paragraph 6, the characteristics and performance of a medical device must not be compromised in a way that endangers the safety of patients, users, or third parties, provided that the product is used under the intended conditions and maintained in accordance with the manufacturer’s instructions. End-of-life tests significantly contribute to meeting this requirement by serving as service life testing for reusable medical devices and verifying compliance with safety and performance requirements throughout the entire service life. This is done by simulating reprocessing cycles in accordance with the MDR.

DIN EN ISO 13485 requires manufacturers to validate and document product specifications, including storage and service life. This requires meaningful verification and validation data.

If the risk assessment indicates that aging can alter the product, then biological safety must be assessed throughout the service life. DIN EN ISO 10993-1 considers the entire product life cycle and requires the assessment of biological risks, including possible changes due to aging.

According to DIN EN ISO 17664-1, manufacturers’ instructions for use should include information on the medical device’s service life. This can be done by referring to indicators of the end of service life, such as physical damage or material wear, or by providing the maximum permitted number of reuses.

According to DIN EN ISO 14971, the service life of a medical device is a key parameter in risk management and is directly related to the total number of uses. It influences the assessment of occurrence probabilities in the risk acceptance matrix. End-of-life testing and the simulation of reprocessing cycles can determine and document this. End-of-life tests provide reliable data that can be used to transparently support assumptions in risk management or to initiate design changes based on results.

End-of-life tests are not isolated laboratory experiments, but rather an integral part of the validation strategy for cleaning, disinfection, and sterilization processes for reusable medical devices. The results of the end-of-life testing must be consistent with the information provided in the reprocessing instructions in accordance with DIN EN ISO 17664-1 and form an essential data basis for cleaning, disinfection, and sterilization validations. End-of-life testing verifies whether a medical device remains safe and functional even after repeated reprocessing and until the end of its intended service life.

The test criteria are based on worst case conditions and reprocessing parameters. From a risk management perspective, the simulations thus provide a specifically answer to the question of whether a product remains within acceptable risk limits given the intended number of uses and reprocessing cycles. For manufacturers of reusable medical devices, service life testing enables the integration of reprocessing validation and service life testing. The results from cleaning, disinfection, and sterilization validations, as well as from reprocessing simulations, can be directly incorporated into the technical documentation in accordance with MDR, DIN EN ISO 13485, and DIN EN ISO 14971.

The expected service life of a medical device influences fundamental decisions regarding the selection of materials, components, surface treatments, and technologies as early as the initial stages of product development. Repeated reprocessing cycles place specific demands on material durability, joining techniques, and functional design - especially when a mix of materials is used (e.g., joints between silicones, plastics, and metals). Accompanying aging tests make it possible to detect potential aging or degradation mechanisms at an early stage. This allows for the identification of structural weaknesses and the targeted implementation of design or material adjustments before a product is placed on the market. Based on the results of lifecycle tests, manufacturers can specifically evaluate alternative materials, optimized coatings, or modified joining techniques, thereby ensuring that the product is designed to meet the required service life.

For the market approval of new products, the simulation of processing cycles serves as a central element of the verification and validation strategy. End-of-life tests conducted early in the development process reduce the risk of last-minute design changes shortly before approval and thus contribute to more stable time-to-market planning. At the same time, reliable service life and reprocessing data are available for technical documentation, clinical evaluation, and communication with notified bodies.

The service life of a medical device is closely linked to the required maintenance, service, and replacement intervals. These intervals must be defined and justified by the manufacturer and documented in the accompanying materials. End-of-life tests help determine these intervals by identifying the point at which material- or function-related changes may begin to occur. The results thus contribute to the transparent establishment of maintenance and servicing measures.

Planning the simulation of assembly cycles begins with a clear definition of the product, its intended use, and the underlying assembly processes. It depends on how well the manufacturer already understands the newly developed product, materials, and joints. If knowledge in this area is limited, a preliminary test to assess durability in the selected process is recommended. The actual test to generate data for the technical documentation can only be conducted once the efficiency validations have been successfully completed. Medical device manufacturers should always use the validated reprocessing procedure as the basis for testing in order to establish a standardized data set. 

On this basis, a stress-relevant scenario, the number of cycles to be simulated, and the product properties to be evaluated are determined. This typically includes the selection and parameterization of the reprocessing procedures, the determination of the number of samples, the definition of time points for interim evaluations (e.g., 0%, 50 %, and 100 % of the intended service life), and the selection of test methods for evaluating material and functional properties as well as biological safety. A clearly structured test plan is essential to ensure that end-of-life tests reliably address both regulatory requirements and internal development objectives.

For tests focused solely on material compatibility, a worst case scenario approach is recommended (e.g., high alkaline detergents, long sterilization times).

Both manual and automated cleaning and disinfection procedures are used for the aging of medical devices. The selection of procedures is product-specific and is based on the recommended reprocessing guidelines or is determined during product development. During manual cleaning with a brush or ultrasound, the mechanical forces acting on the product differ from those in the automated cleaning and disinfection (washer disinfector) process.

To fully simulate the reprocessing cycle, sterilization processes are also simulated. Both steam sterilization methods and low-temperature methods using vaporized hydrogen peroxide (VH₂O₂) are employed. Cycle parameters, process control, and the number of repetitions are defined and documented in accordance with the intended use and the manufacturer’s specifications.

The reprocessed medical devices are evaluated in a structured manner at defined intervals. The goal is to systematically document any potential changes resulting from repeated reprocessing and to assess their relevance to safety and performance. The evaluation primarily consists of visual inspections, functional tests, and biological analyses. Visual assessments identify surface changes such as discoloration, cracking, delamination of coatings, or other material-related changes. Functional tests verify whether moving components, as well as those critical to safety or performance, continue to reliably perform their specified functions even after repeated reprocessing.

In addition, biological safety tests can determine whether repeated reprocessing and accelerated aging significantly alter biological compatibility. These tests are relevant when material changes, degradation processes, or interactions with cleaning and disinfection chemicals cannot be ruled out.

The combination of visual assessments, functional tests, and, where applicable, biological safety tests provides a measurable and traceable representation of the medical device’s lifecycle. The results indicate the maximum number of reprocessing cycles for which the product’s characteristics and performance remain within the specified requirements.

Medical device manufacturers must define the relevant tests and endpoints for such aging. Depending on the specific product, additional requirements may include testing for electrical safety (e.g., dielectric strength) and labeling.

If any anomalies occur during the simulation of reprocessing cycles (such as cracking, loss of function, or corrosion), these must be systematically analyzed and documented. Depending on the severity and relevance to the intended use, this may lead to design modifications, changes in materials, a reduction in the specified service life, or additional risk mitigation measures. It is important that the rationale behind the decisions made is transparently documented in the technical documentation and that a consistent link is established to risk management, reprocessing instructions, and clinical evaluation.

The data generated during the simulation of reprocessing cycles should be incorporated into the technical documentation in a structured manner. This includes a clear description of the test plan - specifying which test items are sampled and tested for what purpose- as well as the reprocessing processes used, the number of simulated cycles, the test methods employed, and the evaluation criteria. Furthermore, consolidating the results within the overall context - end-to-end with respect to the test plan - is important for traceability. This transparency facilitates traceability for notified bodies as part of conformity assessment under the MDR and supports consistency between the risk management dossier, the reprocessing instructions, and the clinical evaluation.

End-of-life tests designed to simulate reprocessing cycles are an essential tool for evaluating the service life of reusable medical devices. Through the structured simulation of reprocessing cycles, they provide reliable and real-world data to ensure safety, performance, and regulatory compliance throughout the entire product lifecycle. By simulating reprocessing cycles, manufacturers of reusable medical devices can conduct robust service life tests that practically meet the requirements of the MDR, DIN EN ISO 13485, DIN EN ISO 14971, DIN EN ISO 10993-1, and DIN EN ISO 17664-1. Conditioning through defined cleaning, disinfection, and sterilization cycles directly links regulatory requirements to the actual stresses the product experiences in everyday clinical use.

As part of end-of-life testing, real-world reprocessing procedures are systematically simulated by replicating reprocessing cycles. This includes complete cleaning, disinfection, and, if applicable, sterilization cycles, which are repeated in accordance with the intended use. The number of cycles is based on the defined service life and the expected frequency of use.

To conduct the simulation, SMP has reprocessing devices from Getinge, Steelco, Belimed, Miele, Dentsply Sirona, MMM, HAWO, and Bandelin at its disposal. All devices are in perfect technical condition, ensuring that reproducible process conditions are maintained. Process parameters are documented either via the respective devices or, on a device-specific basis, through a central process data documentation system. Due to the large number of devices, a contingency plan is in place, and parallel testing enables an increased throughput of processes. The selection of equipment is made in collaboration with the medical device manufacturer and is based primarily on the size of the medical device to be tested, its positioning in the loading rack, and thus the utilization of the WD and sterilizers. The following equipment is available for simulation:

• five large-capacity WD in accordance with DIN EN ISO 15883
• four under-counter or benchtop WD in accordance with DIN EN ISO 15883
• two Dentsply Sirona DAC Universal (for dental transmission instruments) in accordance with DIN EN ISO 15883
• three sterilizers in accordance with DIN EN 285
• two sterilizers in accordance with DIN EN 17180
• one sterilizer in accordance with DIN EN 13060
• Two ultrasonic baths
• three sealing machines

SMP does not perform biological safety testing. We would be happy to put you in touch with a partner laboratory for these tests and organize sample transport and processing on your behalf.

If you have specific requirements for cleaning, disinfection, or sterilization processes for a new or existing medical device, you can work with SMP to develop a customized concept for simulating reprocessing cycles and conducting service life testing.

How is the number of reprocessing cycles to be simulated determined?

The number of simulated reprocessing cycles is derived from the intended service life and the expected frequency of use of the medical device. This is based on assumptions regarding typical clinical use per day/week and the resulting total number of applications over the service life.

Do end-of-life tests always have to fully replicate all real-world reprocessing steps?

All reprocessing steps intended for the product (cleaning, disinfection, and, depending on the classification, sterilization) should be included in the simulation of reprocessing cycles. Deviations or abbreviations are permitted only if they are technically justified and documented, for example, to focus on particularly critical process steps or material stresses.

Which standards are particularly relevant for the simulation of reprocessing cycles?

Depending on the product and its intended use, the following standards apply: DIN EN ISO 17664-1 (reprocessing instructions), DIN EN ISO 13485 (quality management), DIN EN ISO 14971 (risk management), DIN EN ISO 10993-1 (biological evaluation taking aging processes into account), as well as product-specific standards such as DIN EN ISO 15883 or DIN EN ISO 17665. End-of-life tests serve to ensure that the requirements of these standards regarding service life and reprocessing are robust.

How are the results of the simulation of reprocessing cycles incorporated into the technical documentation?

The results are typically included in the technical documentation in the form of test reports, risk assessments, and verification records. They serve as evidence that the specified service life, the maximum number of reuses, and the described reprocessing recommendations are based on validated data. Furthermore, they support the clinical evaluation and the rationale within the framework of conformity assessment according to the MDR.

How does the simulation of reprocessing cycles support risk management in accordance with DIN EN ISO 14971?

The simulation of reprocessing cycles provides quantitative and qualitative data on material- and function-related changes over the entire intended service life of a medical device. This data is incorporated into the assessment of probability of occurrence and severity of harm as part of risk management in accordance with DIN EN ISO 14971. End-of-life tests make it possible to verify assumptions regarding wear and tear, loss of function, or changes in biological safety, and, if necessary, to derive risk control measures such as design modifications, material changes, or a reduction in the specified service life.

How can the maximum number of reuses be determined from the simulation of reprocessing cycles?

The results of the simulation of reprocessing cycles can be used to determine the maximum number of applications and reprocessing cycles for which the specified safety and performance requirements are met. This information is included in the instructions for use in accordance with DIN EN ISO 17664-1 and is justified in the risk management documentation as well as in the technical documentation.

What criteria are used to select the reprocessing methods to be modeled in the simulation of reprocessing cycles?

The selection of reprocessing methods is based on the processes described in the reprocessing instructions. Relevant criteria include thermal and chemical stress, contact times with process chemicals, and the combination of cleaning, disinfection, and sterilization methods.