Page 63 - Safety Risk Management for Medical Devices

42 Safety Risk Management for Medical Devices

As biological evaluation is a component of medical device risk management
activities, it must be planned in advance. This includes: literature searches, biological
evaluations, review and approvals of biological evaluations, and documentation of
residual risks.
In biological evaluations, the safety risk to patient/user is a function of the toxicity
of the materials, their route and duration of exposure, and the physical properties of
the materials. For example, a rough surface creates a larger exposure area than a
smooth surface.
ISO 14971 [3,7] and ISO 10993 [15] require characterization of medical devices
for potential Hazards. This includes the materials themselves, all additives and
processing aids, interaction with sterilization processes, and chemical transformation
of the materials (e.g., degradation) during use. Also consider the interaction with, or
contamination from the packaging materials. Both direct and indirect tissue contact of
medical device materials should be considered.
Factors that can influence the biological safety of medical device materials include:

• Mechanical wear, strain, vibration, and deformation due to use
• Biomechanical interactions such as abrasion, friction, and sticking
• Biochemical interactions such as with acids, and enzymes
• Heat/cold
• Radiation
• Chemicals, such as ethylene oxide in the course of sterilization
• Cleaning solutions
Risk estimation requires two components: (1) the likelihood of exposure to a
Hazard, and (2) the probability of sustaining Harm from the Hazardous Situation.
Determination of the likelihood of exposure to a biological hazard depends on
factors including:

a. The bioavailability of toxic materials—how likely is it for the toxin to become
present?
b. The potential for exposure

Determination of the probability of sustaining Harm in the event of exposure
depends on factors including:

a. The nature of the toxin
b. The quantity of the toxin (dose response)
c. The tissue that is exposed (e.g., intact skin vs mucous membranes)
d. The duration of exposure
e. Geometric properties (e.g., particle size, porosity, surface texture)