Plastics in Medical Devices is a comprehensive overview of the main types of plastics used in medical device applications. It focuses on the applications and properties that are most important in medical device design, such as chemical resistance, sterilization capability and biocompatibility. The roles of additives, stabilizers, and fillers as well as the synthesis and production of polymers are covered and backed up with a wealth of data tables.
Since the first edition the rate of advancement of materials technology has been constantly increasing. In the new edition Dr. Sastri not only provides a thorough update of the first edition chapters with new information regarding new plastic materials, applications and new requirements, but also adds two chapters - one on market and regulatory aspects and supplier controls, and one on process validation. Both chapters meet an urgent need in the industry and make the book an all-encompassing reference not found anywhere else.
- Comprehensive coverage of uses of polymers for medical devices
- Unique coverage of medical device regulatory aspects, supplier control and process validation
- Invaluable guide for engineers, scientists and managers involved in the development and marketing of medical devices and materials for use in medical devices
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PLASTICS IN MEDICAL DEVICES
PROPERTIES, REQUIREMENTS, AND APPLICATIONS
By Vinny R. Sastri
ElsevierCopyright © 2010 Vinny Sastri
All rights reserved.
The global medical device industry is estimated to be between US $220 and $250 × 109 in value. This industry continues to show a healthy growth rate overcoming many economic downturns or slowdowns. It is projected to grow from about US $100 billion to almost US $300 × 109 in 2015. Figure 1.1 shows the growth from 2000 projected to 2013. These numbers are aggregates from various reports and sources. Numbers of the actual market size vary from report to report. The United States has about 40% of the global market share, followed by Europe, Japan, and the rest of the world (Figure 1.2). Germany is the largest market in Europe followed by France, Italy, and the United Kingdom. Japan is the second largest country by market share next to the United States.
The rest of the world comprises regions like China, India, and Latin America. These regions are seeing 10-15% annual growth rates in the medical device market. One of the reasons for this growth is the population increase in these regions compared to the United States and Europe. The Population Reference Bureau projects that the world will have close to 10,000,000,000 people by the year 2050 as shown in Figure 1.3. Most of this growth will come from regions like China, India, Latin America, and Africa. The demand for health care and medical devices as a result continues to increase for these regions and globally as well.
Several factors are affecting the growth of the medical device market. They include the following:
Population growth and aging populations
In addition to population growth mentioned above, populations are aging in countries like the United States, Western Europe, and Japan. People over the age of 65 will increase dramatically over the next 10-20 years. This demographic will require more healthcare diagnostics and surgical procedures like cardiovascular and orthopedic operations. Affordable health care is becoming more accessible to large numbers of people in regions like China and India as the economies of these countries continue to grow. This, coupled with their large populations, will increase the need for medical devices and diagnostics.
Minimally invasive procedures
Shorter hospital stays and the increase in the use of minimally invasive surgeries require innovative, effective disposable devices. These devices are using more electronics, are getting smaller, and require demanding performance during procedures. Biocompatibility and electrical and thermal management will be very important for these devices.
Increase of infectious diseases
With the increase and spread of infectious diseases globally, many prophylactic devices and therapies are required. New drug therapies need to be administered using lipids which can be aggressive on standard plastics during drug delivery. Materials that do not react, degrade, swell, crack, or leach out impurities when in contact with lipids need to be used.
Outpatient and home health care
Home health care and outpatient care require either healthcare providers or individuals to use certain types of devices by themselves. Such devices must be safe, effective, easy to use, and ergonomically well designed. Remote diagnostics will also increase, leading to the need for computerized diagnostic devices that can analyze and send data to doctors and physicians hundreds of thousands of miles away for evaluation and diagnosis.
Research and development in new drugs, biomaterials, biomedical engineering, new procedures, and the increased use of electronics will lead to sophisticated medical devices like sensing devices, ultrahigh resolution imaging systems, combination products (drug-device hybrids), nanodevices, biorobotics, microfluidic devices, molecular diagnostics, and orthopedic implants.
1.2 Medical Device Definition
Medical devices range from simple devices like tongue depressors, syringes, and bandages to highly sophisticated imaging machines and long-term surgical implants. Examples of medical devices include surgical instruments, catheters, coronary stents, pacemakers, magnetic resonance imaging (MRI) machines, X-ray machines, prosthetic limbs, artificial hips/knees, surgical gloves, and bandages.
Medical devices are regulated by the Food and Drug Administration (FDA) in the United States. A medical device as defined by the US FDA is anything used for therapeutic and/or diagnostic purposes in humans or animals, which is not a drug. A medical device as defined by the US FDA is given in Section 201 of the Food Drug and Cosmetic (FD&C) Act. As per this act, "a medical device is an instrument, apparatus, implement, machine, contrivance, implant in vitro reagent, or other similar related article, including any component, part or accessory which is:
1. Recognized in the official National Formulary, or the United States Pharmacopeia, or any supplement to them,
2. 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
3. Intended to affect the structure or any function of the body of man or other animals, and which does not achieve its primary intended purpose through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of its primary intended purposes."
In the European Medical Device Directive a medical device is defined as a product with a medical intended purpose, whether for diagnosis, treatment, or alleviation of a medical condition in humans and is not a drug. As per this directive, "a medical device is defined as any instrument, apparatus, appliance, software, material or other article. This includes if this device is used alone or in combination with software necessary for its proper application intended by the manufacturer to be used for human beings in the purpose of:
1. Diagnosis, prevention, monitoring, treatment or alleviation of disease
2. Diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap
3. Investigation, replacement or modification of the anatomy or of a physiological process control of conception and which does achieve its principal intended action by pharmacological process, immunological or metabolic means but may be assisted in its function by such means."
Devices are classified into three classes: Class I, Class II, and Class III depending upon their risk and criticality. Each device class requires a different level of regulation and compliance. Examples of Class I devices are tongue depressors, bandages, gloves, bedpans, and simple surgical devices. Examples of Class II devices are wheelchairs, X-ray machines, MRI machines, surgical needles, catheters, and diagnostic equipment. Class III devices are used inside the body. Most implants are Class III devices. Examples include heart valves, stents, implanted pacemakers, silicone implants, and hip and bone implants. The Medical Device Directive classifies devices as Class I, Class II, Class IIa, and Class III in order of increasing risk.
1.3 Types of Devices
Medical devices can be classified into two major categories—disposables and nondisposables. Examples of nondisposable devices include machines and instruments, diagnostic equipment, surgical and dental instruments, prostheses, and implants. Examples of disposable devices include bandages, gloves, blood bags, colostomy bags, catheters, syringes, IV kits, and tubing.
Materials used in nondisposable applications must typically meet long-term durability and stringent physical and mechanical properties. Materials used in machines and diagnostic equipment do not necessarily need to be sterilized or meet specific chemical resistance or biocompatibility requirements. Examples of diagnostic and surgical equipment are MRI machines, electrocautery devices, and electro cardiogram (ECG) monitors. Implants on the other hand must meet strict biocompatibility, biodurability, and sterilization requirements to be safe and effective in the body. Active implant devices include pacemakers, artificial cochlear devices to help restore hearing, and implantable neurostimulators used to control pain or incontinence. Nonactive implantable devices include coronary stents for treating vascular disease and knee and hip replacement devices.
Materials used in nondisposable applications must meet processing, assembly, physical, and mechanical requirements specific to the application and intended use. In addition, they may need to have chemical and/or lipid resistance, be resistant to specific sterilization methods, and may also need to be biocompatible and nontoxic. Material and production costs are also important to consider.
There is a wide spectrum of requirements that apply to materials used in medical device applications. It is important to understand these requirements and design the right part with the right material that fits the intended use and the processing and assembly of the finished device.
1.4 Materials Used in Medical Devices
Materials used in the design, production, and assembly of medical devices include metals, ceramics, glass, and plastics. The use of plastics continues to grow especially with the growth in disposable products (Figure 1.4).
Plastics have superior design flexibility compared to metals, ceramics, and glass. They can be processed into innumerable shapes, sizes, thicknesses, and colors, and their properties can be tailored to meet a wide spectrum of physical, mechanical, chemical, and biocompatibility requirements. Additives and fillers can be used to render plastics flexible or rigid, insulating or conductive, hydrophilic or hydrophobic, transparent or opaque, and chemically resistant and sterilization resistant.
Plastics can be processed by many different methods ranging from injection molding and extrusion to machining to form molded parts, films, and fibers. They are lightweight compared to metals, ceramics, and glass and can have an excellent balance of strength, stiffness, toughness, ductility, and impact resistance. Many applications are using plastic to replace either metal or glass to reduce costs, leverage design flexibility, and still maintain performance.
This book classifies plastics into four main categories.
1. Commodity thermoplastics include polyvinyl chloride, polyolefins, and polystyrene. Cyclo olefin copolymer (though not a commodity thermoplastic) has been included in this section.
2. Engineering thermoplastics have improved thermal and mechanical properties over commodity thermoplastics. This polymer family is made up of acrylics, polycarbonates, polyurethanes, acetals, polyesters, and polyamides.
3. High temperature thermoplastics have very high temperature resistance along with excellent strength, stiffness, and toughness. Materials in this family include polyimides, polyetherimides, polysulfones, polyarlyether ketones, liquid crystalline polymers, and fluoropolymers.
4. Other polymers that are used in medical device applications include styrenics, silicones, thermoplastic elastomers, and thermosets.
Figure 1.5 gives an approximate breakdown of their share in medical device applications. Commodities are mostly used in disposable products. Engineering thermoplastics are used in both disposable and nondisposable products. High temperature engineering thermoplastics are used in implants, surgical instruments, and components for machines and equipment.
Table 1.1 summarizes the use of various plastics in medical device applications.
1.5 Medical Devices—Material Selection Process
In designing and developing a medical device, several factors need to be taken into consideration when selecting a potential material. First, it is important to know the component or device's intended use. As mentioned before, requirements of a nondisposable device like diagnostic equipment or imaging parts will be quite different from those of a disposable blood bag, which will be very different from that of a permanent spinal implant. Physical and mechanical properties, thermal and electrical properties, chemical and sterilization resistance, biocompatibility, and joining and welding capabilities are just some of the criteria that must be evaluated in the selection of the appropriate plastic material.
Excerpted from PLASTICS IN MEDICAL DEVICES by Vinny R. Sastri. Copyright © 2010 Vinny Sastri. Excerpted by permission of Elsevier.
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Table of Contents
1. Introduction 2. Regulations for Medical Devices and Application to Plastics Suppliers: History and Overview 3. Materials Used in Medical Devices 4. Material Requirements for Plastics used in Medical Devices 5. Polymer Additives Used to Enhance Material Properties for Medical Device 6. Commodity Thermoplastics: Polyvinyl Chloride, Polyolefins, and Polystyrene 7. Engineering Thermoplastics 8. High-Temperature Engineering Thermoplastics: Polysulfones, Polyimides, Polysulfides, Polyketones, Liquid Crystalline Polymers, and Fluoropolymers 9. Other Polymers: Styrenics, Silicones, Thermoplastic Elastomers, Biopolymers, and Thermosets 10. Supplier Controls 11. Process Validation