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Use of Engineering Polymers in medical devices rises on growing replacement to metals, ceramics, glass

Use of Engineering Polymers in medical devices rises on growing replacement to metals, ceramics, glass


Polymers have gained traction in the medical industry due to their versatile properties. Since the medical polymer market is expected to witness sustained growth, key polymer manufacturers are showing interest to invest to establish themselves as medical polymer manufacturers. As per Nanomarkets, medical polymers are widely used in three major domains: implants and devices; diagnostic systems; and hospital accessories such as pathological, microbiological, and surgical, clinical labware. All of these applications are predicted to see huge growth in terms of size and volume as people across the world are willing to get better medical treatments. Developments in polymer technology are triumphing over certain performance limitations and facilitating these materials to fulfill the rigorous prerequisites of this sector, especially for the implants and devices domain, where the polymers need to be used inside the body. Pertaining to the physical nature of the polymers, the medical polymer market is classified into two categories: plastic resins and fibers and elastomers. They are also segmented into biostable/non-biodegradable or biodegradable. Resins are liquid-soluble polymers, while fibers appear in long elongated shapes. Non-biodegradable medical fibers and resins are rigid plastics such as thermosets, thermally remoldable, and thermoplastics. Thermoplastics are largely used in the healthcare sector as they satisfy the challenging property prerequisites of the medical industry. Additive like rheology modifiers, stabilizers, coloring agent are added to further improve the mechanical properties of plastics. While polymer processing is easier, the risk of additive or unreacted monomer leaching during use needs to be addressed, especially for in-vivo implantable devices. Better processability is required to minimize such side effects, while utmost care must be taken for characterizing any biomaterial to avoid the harmful tissue reaction. Elastomers are materials capable of withstanding large deformations and regaining their original shape when the stress is removed, thus showing a rubber-like elasticity. These materials exhibit a combination of properties such as toughness, resilience, stretchability, and stiffness. Non-biodegradable elastomers include natural rubber, silicon rubber, butyl rubber, polyurethanes, and machined thermoplastic elastomers. In these materials, silicon rubber, polyurethanes, and thermoplastic elastomers have found use in many medical applications. Besides commodity polymers, new-age elastomers are increasingly used in the present medical market. Commercial elastomers produced without physical or chemical cross-links or vulcanization consist of more flexible molecular networks and show both thermoplastic and elastomeric properties, thereby yielding a ‘soft touch.’ The device industry coats accessories with these materials to impart a soft touch feel. Their adoption is expected to increase in blood collection devices, cardio systems¸ intravenous drug delivery systems owing to the fact that engineered thermoplastic elastomers have high barrier properties in addition to other benefits. Engineered polymers or copolymeric products optimize the working efficiency of some of the aforementioned polymers by imparting unique qualities advantageous for medical applications. This approach facilitates imparting significant properties of individual polymer chains into the final product. Sterlizability is another critical quality required for polymers to be used in medical applications because of the necessity of sterilizing all instruments and devices prior to their implantation into the body. Engineered plastics and thermoplastic elastomers are autoclavable and can be sterilized by steam or radiation. However, the challenge is to make them stable where repeatable sterilization cycles are used for different purposes, such as for labware products and diagnostics. Biodegradable polymers are significant to the paradigm shift from biostable polymers, especially for enabling drug delivery in a controlled manner while leaving trace material inside the body. It is predicted that entire prostheses will be produced from biodegradable polymers in the near future. Biodegradable polymers will be widely used in implants and some clinical labware, but not in the production of diagnostic products. In fact, biodegradable polymers coatings can be found in some commercially available drug eluting stents. Leaching of small molecules during use is the major drawback for biodegradable polymers. Currently, natural polymers and degradable polymers earned the approval of regulatory bodies like the FDA are predominant. Although there is more interest in determining new biodegradable polymers for medical purpose, investment in this field is limited because of the need to complete comprehensive long-term studies for validating new materials.

As per Strategic Business Insights, one of the main reasons behind the increasing use of Engineering Polymers (EPs) in medical devices is the quest by engineers to replace traditional materials such as metals, ceramics, and glass with better materials. Some EPs have several advantages over traditional materials, which can include weight, biocompatibility and cost. Concerns in 2012 surrounding the wear and corrosion of metal-on-metal (MoM) hip implants have also led to a surge in the medical community's uptake of implants containing EPs.
EPs such as polyetheretherketone (PEEK), polyetherimide, polyphenylsulfone and polysulfone saw first use in experimental medical implants in the 1980s. Researchers then went on to conduct in-depth clinical studies in the 1990s that helped characterize the biocompatibility and in vivo stability of EPs. However, further progress was impeded by the reluctance of polymer manufacturers to supply the health-care market following a series of lawsuits against Dow Corning in the 1990s. These lawsuits claimed that Dow Corning's silicone breast implants caused systematic health problems and eventually resulted in Dow Corning's agreeing to a multi-billion-dollar settlement for victims. To protect the chemical and plastics industry from future lawsuits, the US government established the US Biomaterials Assurance Act (BAAA) in 1998 and placed the burden of responsibility for any device failure on the manufacturer, not the material supplier. The BAAA's reassurances to suppliers meant that the number of EP manufacturers seeking entry into the health-care market slowly grew in the next decade. In 2007, Solvay provided a notable entry by a leading EP manufacturer into the health-care market. Since then, the number of EP suppliers to follow suit has risen significantly, partly because of the relative stability of the health-care market, which has been sheltered from much of the impact of the global economic crisis that began in 2008.
Although the strategic maneuvering of suppliers is indicative of an increase in demand for EPs, medical-device makers are the real driving force behind the growth in this sector. One indicator of medical-device manufacturers' growing interest in EPs is the rising number of US Food and Drug Administration (FDA) 510(k) clearances. FDA 510(k) clearances are necessary for companies introducing new medical devices into the US market. In 2001, only one FDA 510(k) clearance with a PEEK polymer featured in the registered name of an implantable device. Since 2001, the FDA has granted 97 such clearances, with the past two years (2011–12) accounting for 33% of these clearances. One reason why device manufacturers are looking for a shift from traditional materials to EPs is that high-performance engineering polymers—such as PEEK—are less expensive than medical-grade metals such as titanium. Many EPs also have excellent chemical, thermal, and mechanical stability and are radiolucent, making implants compatible with a range of medical-imaging tools. Devices made from PEEK show the lowest wear rate of any counter metallic material. An FDA enquiry in June 2012 called into question the safety and durability of MoM implants and concluded that it sees little use for MoM implants, favoring a greater use of ceramic and plastic alternatives in the future. Regulatory warnings from the FDA surrounding MoM implants may also become a significant contributory factor in future decision making about the type of material that goes into medical implants.
As per Strategic Business Insights, application of EPs in medical implants typically falls into three categories:
Spinal Implants : Device manufacturers use high-performance engineering polymers in a variety of spinal implants, including lumbar and cervical spacers. Surgeons typically use spacer units in spinal-fusion operations, a process in which surgeons fuse two or more vertebrae so that they can become a single strengthened unit - a procedure that helps protect the sensitive nerves running alongside the spinal column. Lumbar and cervical spacers typically contain a bone-graft material that, once implanted, promotes bone healing and facilitates the fusion. Many of the screws and rods that surgeons use to stabilize the spine further are also made of high-performance polymers. The use of EPs in spinal implants offer numerous advantages over the use of metals - such as titanium - including a similar elasticity to that of bone, helping to reduce jarring during situations of impact. Because of these advantages, the use of PEEK in spinal implants is becoming commonplace, with the number of FDA 510(k) clearances accelerating during 2012. Many of these clearances come from small start-up companies, such as Nexxt Spine and SpineNet, that specialize in the manufacture of unique cervical and lumbar spacers using Solvay's Zeniva PEEK.
Cranial Injuries : The cranial-implant market is dominated by a number of medical-device manufacturers, including Synthes, which has been providing custom-fit cranial implants since 2004. The cranial implants themselves have traditionally been made from metals - such as titanium - and customized using patients' computed tomography data and computer-aided design/computer-aided manufacturing. Manufacturers such as Synthes are now starting to move away from the use of metal in preference for high-performance EPs because of their lower cost and improved biocompatibility. Choice of material is not the only aspect of implants that medical-device manufacturers are changing. The means of manufacture is also changing, with 3D printing seeing increasing use. In December 2011, the Custom IMD group, an EU–backed initiative, designed and manufactured the first laser-sintered PEEK cranial implant. Working in conjunction with EOS, the Custom IMD group used a unique sintering system that operated at temperatures up to 385°C, necessary for processing PEEK. One of the advantages of using 3D printing to manufacture these implants is that surgeons can design implants to include highly complex structures. The prototype designed by the Custom IMD group comprised a structured PEEK mesh that was subsequently filled with a bioabsorbable polymer/ceramic hybrid material. The Custom IMD group demonstrated that the combination of the mesh and the bioabsorbable polymer allowed the gradual infiltration of a patient's own bone cells and promoted natural bone growth. The demand for custom-made implants using additive-manufacturing techniques is likely to increase as the capabilities of 3D printing continue to expand.
Hip and Joint Replacements : Researchers at the Fraunhofer Institute for Manufacturing and Automation in Stuttgart, Germany, part of the EU-backed ENDURE (Enhanced Durability Resurfacing Endoprosthesis) project, are currently working on the final design of a prototype hip replacement. The project's design comprises a hip socket made of carbon-fiber-reinforced PEEK in combination with a ceramic femoral head. The prototype has several distinct advantages over traditional hip replacements. Aside from being metal free, the prototype hip replacement works with the natural shape of the joint instead of removing large sections of the existing bone structure. In doing so, the transmission of force through the PEEK hip socket to the pelvic bone is modeled on natural conditions, thus avoiding any potential adverse bone adaptation. In a separate study in September 2012, researchers at the University of Glasgow (Scotland) published their findings about the use of PEEK in hip implants. In traditional hip-replacement surgery, surgeons remove the head of the femoral bone and replace it with an implant, which is held in place by a rod fixed inside the marrow along the length of the bone. One of the problems associated with using this technique with a metal rod is that stem cells in the bone marrow tend to differentiate into soft tissue, leading to the loosening of the implant, typically limiting the lifetime of the implant to about 20 years. The researchers at Glasgow found that PEEK implants may potentially go some way to solving this problem and creating an "implant for life."
In collaboration with the University's James Watt Nanofabrication Centre, the researchers at Glasgow produced a PEEK sample with nanopatterns of tiny holes—about 120 nanometers in diameter—along the surface. When they placed stem cells on the surface of the PEEK sample, the stem cells diffused into the pores and, unlike metal, preferentially differentiated into bone cells, creating a much stronger bond between the PEEK and the surrounding tissue. The researchers believe that this technique could apply to a wide range of joint replacements and other orthopedic surgeries and are hoping to see a prototype ready for use within a decade, as per Strategic Business Insights. The demand for EPs within the health-care market will be driven not only by advances in manufacturing and new applications but also by the growing markets of Asia: Japan, with its high-age population, will be a large target audience for medical implants and devices, and China is set to become one of largest marketplaces for medical devices and implants, driven by radical health-care reform and a rapidly growing middle class able to afford implant surgeries.

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