March 22, 2023

Biological Evaluation for Reusable Devices: Shelf Life vs. Expected Life

Biological evaluation for reusable devices may reasonably not be focused on “shelf life”. The heart of this question hinges first on general medical device principles regarding shelf life (or lack thereof) vs. stability over the device’s lifetime.  Much can be said about that, so I won’t go too far down the rabbit hole about that here unless otherwise requested.  But in summary, it has been established that not all medical devices have, or need, a shelf life. Yet all devices have a life-cycle within which there is an “expected life” (U.S. FDA), lifetime (ISO 13485, ISO/TN 24971), expected lifetime (EU MDR), etc.

Accordingly, I don’t believe that ISO 10993-1:2018 clause 4.7 (“The biological safety of a medical device shall be evaluated by the manufacturer over the whole life-cycle of a medical device.“) means that shelf life is an important point of biological evaluation for any medical device.  Instead, the device’s shelf life is germane only if the device has a shelf life.

For example, reusable devices oftentimes don’t have or need a shelf life, but instead will always have an expected useful life.  Accordingly, clause 4.7 certainly requires understanding of the biological safety throughout a labeled shelf life if any such shelf life there may be.  But ultimately, for a reusable device, the main focus is generally on biological evaluation representative of the reusable device’s expected useful life, which factors in stability considerations such as material aging, response to reprocessing, etc.  For example, ISO 10993-1:2018 states that if a medical device is intended to change during its lifetime, then the evaluation shall consider all the different device states.  I would expand that to whenever the medical device does/can change during its lifetime.