For many sterile surgical products the question of date expiry is really only one of package integrity. For TissuePatch however, where the product contains an active surface that will chemically bond to a tissue surface, things are a little different. How do we know whether TissuePatch will perform the same way after three years as it does on day 1? How do we know its active chemistry doesn’t deteriorate in the packaging? How do we know under what storage conditions the product needs to be held in order to preserve its function? The answer is really quite simple….we test it, we store it for the requisite time under conditions we expect to be desirable and attainable, and then we test it again….not just one sample, but literally hundreds. What parameters do we test? Every parameter that impacts performance, so dry tensile strength, wet tensile strength, handling, quantitative adhesion, packaging integrity and so on. The good news is that the product has never failed these tests in our hands….which is how we were able to increase shelf life to three years in ambient(25 degC) conditions from the original one year in the fridge. Occasionally we will test product returned from the field, and (has been demonstrated this week in fact) we are always gratified that the performance is sustained. It may not improve like a fine wine, and different vintages are not likely to differ to any meaningful degree, so don’t expect us to be able to tell you which year represented the best vintage.