Medical device lifetime expectancy is currently a hot topic in the industry, given the European medical device regulations requirement, EU MDR 2017/745, Article 18 1(c). Article 83 Post Market surveillance, Article 86 Periodic safety update report, Annex XIV Part B -post-market clinical follow-up are also linked with the expected device lifetime of the device. Manufacturers are required to provide definite expected lifetime for the certification of their product under the new EU medical device regulations. There have been numerous discussions around how to best define the expected device lifetime and what elements should be considered while defining it.
Defining the 'expected device lifetime' of a medical device
Let’s take a look at the definition of expected device lifetime. “It is a period during which the device is intended to perform its function per the risk and benefit profile of a medical device, and maintain its benefits without adding an incremental risk to the patient.” Overall, the expected medical device lifetime may fall within the intended use as specified in the considerations listed below (MedTech Europe Paper).
Consideration 1: The lifetime of devices that are intended to be used only for a specific period (i.e. catheters to deploy a stent) is defined based on their use duration.
Consideration 2: The lifetime of devices that are intended to fully replace a body function (i.e. a joint in the human body) would be ideal for the rest of the patient’s lifetime. It is acknowledged that state-of-the-art devices for the intended use may have a finite service life and may need to be removed/replaced based on physician follow-up and evaluation.
Consideration 3: The lifetime of devices that are intended to function in the body for a limited time (i.e. absorbable implants) is defined by their therapeutic lifetime, their function plus the remaining time to absorption dwelling in the human body.
Consideration 4: The lifetime of devices that have a temporary function in the human body (i.e. implants for bone healing or non-absorbable sutures), is defined by their function in the human body up until the point of removal.
Each consideration listed above could comprise many elements, which are explained in this article. It is essential to understand that the lifetime of a medical device may or may not be based on a single element. Instead, it is a combination of multiple characteristics to carefully identify the safety duration. Elements include patient outcome, product design, clinical utility, observed product performance, benefits and risks, including positive/negative impact on clinical outcome, the patient’s quality of life, outcomes related to diagnosis, and positive/negative implications from diagnostic devices on clinical outcomes. There are external factors that could contribute such as patient anatomy, disease progression. Depending upon the breadth of external factors, there may not be a specific duration instead based on the bench testing; therefore, for state of the art medical device, manufacturers must consider real-life factors and provide necessary instructions thereafter to establish the safe performance.
First, it is imperative to understand the medical device in scope, which will dictate which elements apply and align the outcome accordingly. To begin with, it is necessary to identify the primary element first, which at a high level defines the overall function of the device in the body, followed by the secondary supporting elements such as residual risk. Not every element applies to the type of device in scope. Let’s dive into each of these elements a little deeper and understand the correlation with device lifetime.
- Reliability/durability testing:
Reliability testing is a critical component that directly resonates in defining device lifetime. Reliability testing is the time duration during which a device is tested to several cycles or periods of use of the medical device, based on real-life testing of the medical device. Review bench test verification and durability testing conducted based on relevant standard(s) to evaluate the performance of the respective medical device to assure the product/system design will conform to user needs, given the use environment (in-vitro data).
Fatigue testing is performed as a reliability and durability measure. It is the process of applying cyclic loading progressively leading to a permanent structural change occurring in a material subjected to relevant conditions that produce fluctuating stresses and strains at some points and may affect the product after a sufficient number of cycles/fluctuations. It isn’t necessary to have an infinite number of cycles to cause the structural damage, instead it will be based on the standards recommended for the type of classification and usage of the device.
- Clinical performance:
The clinical performance attributes define the clinical significance of the device and provide clinical results confirming the findings from the bench test. It includes confirmation to support the performance attributes of the device., patient outcome, etc. Depending upon the device classification, clinical performance validates the bench testing and asserts the expected medical device lifetime.
Evaluate the performance and safety of the device through clinical literature, investigations, pre-clinical assessments, ongoing studies, etc., for the intended clinical use of the device.
- Residual risk:
(Note: For implantable devices, the residual risk that results from the entire period of residence of the device inside the patient’s body):
The risk management process involves the evaluation of residual risk over the life of the product. The benefits are compared to the residual risks to ensure risk acceptability is justified. Refer to details on the risk assessment and benefit/risk acceptability conclusion for this product.
When determining the appropriate expected device lifetime, it is important to consider whether certain risks are introduced for certain phases of the potential product lifetime—and whether those risks are acceptable or appropriate to discontinue use of the product to avoid the risks. The risk considerations pertinent to the expected device lifetime for this product are described below.
Example: This product has been tested for reliability performance out to five years. Beyond five years, the potential for increased residual risk due to product failures has been considered; however, this risk is deemed acceptable due to the product performance monitoring and associated corrective actions process, which may be used to address unexpected increases in patient risk.
Clinical evaluation: The decision to use a medical device in the context of a clinical procedure requires the residual risks to be balanced against the anticipated benefits of the procedure. Explain the device's clinical performance and benefits, the circumstances of use, and why it outweighs the risks. Evaluate the medical device performance attributes affirm its integrity; utilize clinical studies to supplement the justification.
Also, evaluate if any characteristics related to degradation of the clinical performance of a medical device can result in unacceptable risk to essential performance.
Post-market surveillance: If applicable and available, utilize post-market surveillance information to support how the observed performance is within the predicted performance defined in the risk management plan/report. If any indicators observed during the commercial history of the product or any significant or critical risk currently present in the field, provide an in-depth evaluation of why the risk is acceptable over the expected device lifetime.
- Shelf life/expiry date of the medical device:
Shelf life is typically used to define the expected lifetime of a single-use device. Shelf life is the established term or period during which a product remains suitable for the intended use, as demonstrated by objective evidence. The product's shelf life dictates how long you can expect a product to maintain expected safety and performance, measured from the date of manufacture to a validated endpoint. This length of time varies, depending on the type of product, how it is used, and how it is stored. Depending on the usage of the device, the shelf life may account for the expected lifetime of a medical device or provide the life of a device to function as intended. Additional information is provided below for the consideration of shelf-life determination.
Note: Shelf life/expiry date pertains to the use by date. If the device includes an implant, the implant's life should not be confused with the use-by date of the entire device.
Material degradation: An expiration date is the termination of shelf life, after which a medical device may no longer function as intended. Degradation or anticipated degradation is the established timeline after which the product or component is expected to decline in quality or effectiveness. To determine if a device requires an expiration date, several different parameters must be considered. The device must be analyzed to determine if it is susceptible to degradation that would lead to functional failure and the level of risk that the failure would present. Assess if the medical device in scope depends on certain component characteristics or expiry date; this assessment is used to determine the overall expected medical device lifetime.
Packaging stability: The stability of packaging material is the extent to which a product within it retains as is, within specified limits, and throughout its period of storage and use. It is the established period that the product has been validated to meet all predetermined design, quality, and effectiveness requirements.
Sterility assurance: Sterility assurance is a crucial component in determining the safety of a medical device. Sterility should be maintained during the entire period of transportation, storage, and use. The level of cleaning and disinfection needed depends on the use of the device. All reusable devices need to be able to clean at some level, and that level depends on the risk of the device. Single-use devices must maintain the sterility level for the expected lifetime of the device. Depending on the device's usage, the device's sterility could impact the expected safe use of the device, thus defining the lifetime.