The living body is an aggressive environment for almost all types of foreign materials, devices, prostheses, and artificial organs which are in contact with the tissues or body fluids of the living body. This aggressive environment can potentially produce changes in the chemical, physical, mechanical, and structural properties of biomaterials, i.e., biodegradation. The vast majority of biomedical polymers used today as biomaterials or in prostheses, devices, or artificial organs are considered biostable and are expected to resist the influence of the in vivo environment for the lifetime of the device or patient while retaining the necessary properties that fulfill the intended functions. In contrast, biodegradable or bioresorbable biomedical polymers are designed to be degraded and eliminated from the body by normal metabolic and physiological processes without adversely affecting body fluids, tissues, and organs.

The term “biostability” commonly refers to the relative stability of biomedical polymers in the physiological environment as a function of time. It is advantageous to discuss biostability and biodegradation of biomedical polymers together. In vivo physiological mechanisms leading to changes in the properties of biomedical polymers are considered to be biodegradation phenomena, while biostable materials are considered to be those materials where physiological interactions do not lead to material property changes and loss of function during the service life of the biomedical polymer.