Chapter 1
OVERVIEW

Joaquim De Ciurana Gay, Tugrul Özel and Lidia Serenó

Department of Mechanical Engineering and Industrial Construction, University of Girona, Girona, Catalonia, Spain

Department of Industrial and Systems Engineering, School of Engineering, Rutgers University, Piscataway, NJ, USA

1.1 INTRODUCTION

Medical devices are defined as articles that are intended to be used for medical purposes. Several official definitions exist for the term "medical device" depending on the geographic market. Therefore, *medical device definition, classification, and regulation follow market location and governmental regulations according to the required level of control considering invasiveness, contact to the patient, and potential risk in case of misuse or failure. This situation concerning the differences in classification strategies has blocked the spread of innovative medical devices across countries. Nevertheless, in 2011, the International Medical Device Regulators Forum (IMDRF) was conceived to discuss future directions to harmonize the medical device regulatory field and accelerate international convergence.

Two of the most important medical device markets worldwide are the European and the North American. Therefore, the official definitions and classifications of both regions are detailed in this chapter.

For the European market, medical devices are governed by a regulatory framework of three directives:

• 93/42/EEC: Medical Devices Directive (MDD)
• 90/385/EEC: Active Implantable Medical Device Directive (AIMDD)
• 98/79/EC: In vitro diagnostic medical devices (IVDMD)

According to them, a medical device is defined as "any instrument, apparatus, appliance, software, material or other article, whether used alone or in combination, including the software intended by its manufacturer to be used specifically for diagnostic and/or therapeutic purposes and necessary for its proper application, intended by the manufacturer to be used for human beings for the purpose of:

• diagnosis, prevention, monitoring, treatment or alleviation of disease,
• diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap,
• investigation, replacement or modification of the anatomy or of a physiological process,
• control of conception,

and which does not achieve its principal intended action in or on the human body by pharmacological, immunological or metabolic means, but which may be assisted in its function by such means."

Similarly, for the North American market and as a part of the Federal Food Drug and Cosmetic Act (FDC Act), a medical device is defined as "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:

• recognized in the official National Formulary, or the United States Pharmacopeia, or any supplement to them,
• intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or
• intended to affect the structure or any function of the body of man or other animals, and which does not achieve its primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent on being metabolized for the achievement of any of its primary intended purposes."

Therefore, any product labeled, promoted, or used in a manner that meets the above-mentioned definition will be regulated by the US Food and Drug Administration (US FDA) as a medical device and will be subjected to pre- and postmarketing regulatory controls.

Both definitions of medical devices exclude other regulated products such as drugs, the primary intended use of which is achieved through chemical action or by being metabolized by the body, biological products including blood and blood products, or products used with animals.

In order to classify a medical device, the manufacturer should, first of all, decide whether the product concerned is considered a medical device as defined in the previous section. Then, depending on the situation, medical devices can be classified following national or governmental rules. In this chapter, the classification given is based on the European Union (EU) and the US FDA regulations.

According to the EU, the classification of medical devices is based on the potential risks associated with the devices. This approach allows the use of a set of criteria that can be combined in various ways and be applied to a vast range of different medical devices and technologies. These criteria are referred to as the "classification rules" and are described in Annex IX of Directive 93/42/EEC. Therefore, the medical device manufacturer must determine the type of device following the rules listed in Annex IX. The rules depend on a series of factors including

• duration: how long the device is intended to be in continuous use,
• invasiveness: whether or not the device is invasive or surgically invasive,
• type: whether the device is implantable or active,
• function: whether or not the device contains a substance, which in its own right is considered to be a medicinal substance and has action ancillary to that of the device,

and are divided as follows:

• Rules 1-4: for noninvasive devices,
• Rules 5-8: for invasive devices,
• Rules 9-12: for active devices,
• Rules 13-18: special rules for products that merit a higher classification than they might otherwise be assigned.

When multiple rules apply, the manufacturer must use the highest risk class. Nevertheless, a small number of products may be more difficult to classify due to their unusual nature or situations where the classification would result in the wrong level of conformity assessment in light of the hazard represented by the devices.

Furthermore, based on these rules described in Directive 93/42/EEC, the devices are divided into four classes, ranging from low risk to high risk:

• Class I: low-risk medical devices,
• Class IIa: medium-risk medical devices,
• Class IIb: medium-risk medical devices,
• Class III: high-risk medical devices.

Thus, in order to classify a medical device, the manufacturer must determine the classification of the medical device (class I, class IIa, class IIb, or class III) considering the Annex IX rules described later. Then, a notified body has to carry out the appropriate conformity assessment procedure to validate and confirm the classification.

As an example, a manufacturer willing to classify a silicone tracheal stent must consider the rules associated with an invasive medical device (Rules 5-8):

• Rule 5 (invasive in body orifice or stoma-not surgically) If it is for transient use Class I If it is for short-term use Class IIa However, if it is for oral cavity, ear canal, or nasal cavity Class I If it is for long-term use Class IIb However, if it is for oral cavity, ear canal, or nasal cavity and it will not be absorbed by the mucous membrane Class IIa If it is connected to an active medical device in class IIa or higher Class IIa
• Rule 6 (surgically invasive-transient use) If it is surgically invasive for transient use Class IIa If it is used to control/diagnose/monitor/correct a defect of the heart or the central circulatory system through direct contact Class III If it is used for the central nervous system (direct contact) Class III If it is a reusable surgical instrument Class I If it is used to supply energy or ionizing radiation Class IIb If it has a biological effect (mainly or wholly absorbed) Class IIb If it is intended to administer medicines in a potentially hazardous manner Class IIb
• Rule 7 (surgically invasive-short-term use) If it is surgically invasive for short-term use Class IIa If it is used to control/diagnose/monitor/correct a defect of the heart or the central circulatory system through direct contact Class III If it is used for the central nervous system (direct contact) Class III If it is used to supply energy or ionizing radiation Class IIb If it has a biological effect (mainly absorbed) Class III If it undergoes chemical changes in the body, or if it administers medicines (not in teeth) Class IIb
• Rule 8 (surgically invasive-long-term use or implantable devices) If it is surgically invasive for long-term use or if it is...