Implant (medicine)

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Orthopedic implants to repair fractures to the radius and ulna. Note the visible break in the ulna. (right forearm) X-ray3.jpg
Orthopedic implants to repair fractures to the radius and ulna. Note the visible break in the ulna. (right forearm)
A coronary stent -- in this case a drug-eluting stent -- is another common item implanted in humans. Taxus stent FDA.jpg
A coronary stent — in this case a drug-eluting stent — is another common item implanted in humans.

An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue. The surface of implants that contact the body might be made of a biomedical material such as titanium, silicone, or apatite depending on what is the most functional. [1] In some cases implants contain electronics e.g. artificial pacemaker and cochlear implants. Some implants are bioactive, such as subcutaneous drug delivery devices in the form of implantable pills or drug-eluting stents. [2]

Medical device Any instrument, apparatus, implant, in vitro reagent, or similar or related article used for diagnostic and/or therapeutic purposes

Simply put, a medical device is any device used for medical purposes. Thus what differentiates a medical device from an everyday device is its intended use. Medical devices benefit patients by helping health care providers diagnose and treat patients and helping patients overcome sickness or disease, improving their quality of life. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and efficacious with reasonable assurance before regulating governments allow marketing of the device in their country. As a general rule, as the associated risk of the device increases the amount of testing required to establish safety and efficacy also increases. Further, as associated risk increases the potential benefit to the patient must also increase.

Biomedical tissue is biological tissue used for organ transplantation and medical research, particularly cancer research. When it is used for research it is a biological specimen.

Biomaterial

A biomaterial is any substance that has been engineered to interact with biological systems for a medical purpose - either a therapeutic or a diagnostic one. As a science, biomaterials is about fifty years old. The study of biomaterials is called biomaterials science or biomaterials engineering. It has experienced steady and strong growth over its history, with many companies investing large amounts of money into the development of new products. Biomaterials science encompasses elements of medicine, biology, chemistry, tissue engineering and materials science.

Contents

Applications

Implants can roughly be categorized into groups by application:

Sensory and neurological

Sensory and neurological implants are used for disorders affecting the major senses and the brain, as well as other neurological disorders. They are predominately used in the treatment of conditions such as cataract, glaucoma, keratoconus, and other visual impairments; otosclerosis and other hearing loss issues, as well as middle ear diseases such as otitis media; and neurological diseases such as epilepsy, Parkinson's disease, and treatment-resistant depression. Examples include the intraocular lens, intrastromal corneal ring segment, cochlear implant, tympanostomy tube, and neurostimulator. [1] [2] [3]

Perception organization, identification, and interpretation of sensory information in order to represent and understand the environment

Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information, or the environment.

Cataract clouding of the lens inside the eye, which leads to low vision

A cataract is a clouding of the lens in the eye which leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry vision, halos around light, trouble with bright lights, and trouble seeing at night. This may result in trouble driving, reading, or recognizing faces. Poor vision caused by cataracts may also result in an increased risk of falling and depression. Cataracts cause half of all cases of blindness and 33% of visual impairment worldwide.

Glaucoma eye disease that is characterized by an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function

Glaucoma is a group of eye diseases which result in damage to the optic nerve and vision loss. The most common type is open-angle glaucoma with less common types including closed-angle glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Peripheral vision may begin to decrease followed by central vision resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent.

Cardiovascular

Cardiovascular medical devices are implanted in cases where the heart, its valves, and the rest of the circulatory system is in disorder. They are used to treat conditions such as heart failure, cardiac arrhythmia, ventricular tachycardia, valvular heart disease, angina pectoris, and atherosclerosis. Examples include the artificial heart, artificial heart valve, implantable cardioverter-defibrillator, cardiac pacemaker, and coronary stent. [1] [2] [3]

Circulatory system Organ system for circulating blood in animals

The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients, oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis.

Heart valve A heart valve allows blood to flow in only one direction through the heart

A heart valve normally allows blood to flow in only one direction through the heart. The four valves are commonly represented in a mammalian heart that determines the pathway of blood flow through the heart. A heart valve opens or closes incumbent on differential blood pressure on each side.

Heart failure condition in which the heart is unable to provide sufficient pump action

Heart failure (HF), also known as chronic heart failure (CHF), is when the heart is unable to pump sufficiently to maintain blood flow to meet the body's needs. Signs and symptoms of heart failure commonly include shortness of breath, excessive tiredness, and leg swelling. The shortness of breath is usually worse with exercise, while lying down, and may wake the person at night. A limited ability to exercise is also a common feature. Chest pain, including angina, does not typically occur due to heart failure.

Orthopedic

Orthopaedic implants help alleviate issues with the bones and joints of the body. They're used to treat bone fractures, osteoarthritis, scoliosis, spinal stenosis, and chronic pain. Examples include a wide variety of pins, rods, screws, and plates used to anchor fractured bones while they heal. [1] [2] [3]

Orthopedic surgery medical specialty concerned with the human apparatus of movement

Orthopedic surgery or orthopedics, also spelled orthopaedics, is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal trauma, spine diseases, sports injuries, degenerative diseases, infections, tumors, and congenital disorders.

Bone fracture medical condition in which there is physical damage to the continuity of the bone

A bone fracture is a medical condition in which there is a partial or complete break in the continuity of the bone. In more severe cases, the bone may be broken into several pieces. A bone fracture may be the result of high force impact or stress, or a minimal trauma injury as a result of certain medical conditions that weaken the bones, such as osteoporosis, osteopenia, bone cancer, or osteogenesis imperfecta, where the fracture is then properly termed a pathologic fracture.

Osteoarthritis Form of arthritis caused by degeneration of joints

Osteoarthritis (OA) is a type of joint disease that results from breakdown of joint cartilage and underlying bone. The most common symptoms are joint pain and stiffness. Initially, symptoms may occur only following exercise, but over time they may become constant. Other symptoms may include joint swelling, decreased range of motion, and, when the back is affected, weakness or numbness of the arms and legs. The most commonly involved joints are those near the ends of the fingers, at the base of the thumb, neck, lower back, knee, and hips. Joints on one side of the body are often more affected than those on the other. Usually the symptoms develop over some years. They can affect work and normal daily activities. Unlike other types of arthritis, only the joints are typically affected.

Metallic glasses based on magnesium with zinc and calcium addition are tested as the potential metallic biomaterials for biodegradable medical implants. [4] [5]

Patient with orthopaedic implants sometimes need to be put under magnetic resonance imaging (MRI) machine for detailed musculoskeletal study. Therefore, concerns have been raised regarding the loosening and migration of implant, heating of the implant metal which could cause thermal damage to surrounding tissues, and distortion of the MRI scan that affects the imaging results. A study of orthopaedic implants in 2005 has shown that majority of the orthopaedic implants does not react with magnetic fields under the 1.0 Tesla MRI scanning machine with the exception of external fixator clamps. [6] However, at 7.0 Tesla, several orthopaedic implants would show significant interaction with the MRI magnetic fields, such as heel and fibular implant. [7]

Magnetic resonance imaging non-destructive technique for imaging internal structures of objects or organisms

Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body in both health and disease. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from CT or CAT scans and PET scans. Magnetic resonance imaging is a medical application of nuclear magnetic resonance (NMR). NMR can also be used for imaging in other NMR applications such as NMR spectroscopy.

The tesla is a derived unit of the magnetic induction in the International System of Units.

Heel part of the foot

The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus or heel bone, behind the articulation of the bones of the lower leg.

Electric

Electrical implants are being used to relieve pain and suffering from rheumatoid arthritis. The electric implant is embedded in the neck of patients with rheumatoid arthritics, the implant sends electrical signals to electrodes in the vagus nerve. [8] The application of this device is being tested an alternative to medicating sufferers of rheumatoid arthritis for their lifetime. [9]

Contraception

Contraceptive implants are primarily used to prevent unintended pregnancy and treat conditions such as non-pathological forms of menorrhagia. Examples include copper- and hormone-based intrauterine devices. [2] [3] [10]

Cosmetic

Cosmetic implants — often prosthetics — attempt to bring some portion of the body back to an acceptable aesthetic norm. They are used as a follow-up to mastectomy due to breast cancer, for correcting some forms of disfigurement, and modifying aspects of the body (as in buttock augmentation and chin augmentation). Examples include the breast implant, nose prosthesis, ocular prosthesis, and injectable filler. [1] [2] [3]

Other organs and systems

Other types of organ dysfunction can occur in the systems of the body, including the gastrointestinal, respiratory, and urological systems. Implants are used in those and other locations to treat conditions such as gastroesophageal reflux disease, gastroparesis, respiratory failure, sleep apnea, urinary and fecal incontinence, and erectile dysfunction. Examples include the LINX, implantable gastric stimulator, diaphragmatic/phrenic nerve stimulator, neurostimulator, surgical mesh, and penile prosthesis. [2] [3] [11] [12] [13] [14] [15]

Classification

United States classification

Medical devices are classified by the US Food and Drug Administration (FDA) under three different classes depending on the risks the medical device may impose on the user. According to 21CFR 860.3, Class I devices are considered to pose the least amount of risk to the user and require the least amount of control. Class I devices include simple devices such as arm slings and hand-held surgical instruments. Class II devices are considered to need more regulation than Class I devices and are required to undergo specific requirements before FDA approval. Class II devices include X-ray systems and physiological monitors. Class III devices require the most regulatory controls since the device supports or sustains human life or may not be well tested. Class III devices include replacement heart valves and implanted cerebellar stimulators. Many implants typically fall under Class II and Class III devices. [16] [17]

Complications

Complications can arise from implant failure. Internal rupturing of a breast implant can lead to bacterial infection, for example. Ruptured implant.JPG
Complications can arise from implant failure. Internal rupturing of a breast implant can lead to bacterial infection, for example.

Under ideal conditions, implants should initiate the desired host response. Ideally, the implant should not cause any undesired reaction from neighboring or distant tissues. However, the interaction between the implant and the tissue surrounding the implant can lead to complications. [1] The process of implantation of medical devices is subjected to the same complications that other invasive medical procedures can have during or after surgery. Common complications include infection, inflammation, and pain. Other complications that can occur include risk of rejection from implant-induced coagulation and allergic foreign body response. Depending on the type of implant, the complications may vary. [1]

When the site of an implant becomes infected during or after surgery, the surrounding tissue becomes infected by microorganisms. Three main categories of infection can occur after operation. Superficial immediate infections are caused by organisms that commonly grow near or on skin. The infection usually occurs at the surgical opening. Deep immediate infection, the second type, occurs immediately after surgery at the site of the implant. Skin-dwelling and airborne bacteria cause deep immediate infection. These bacteria enter the body by attaching to the implant's surface prior to implantation. Though not common, deep immediate infections can also occur from dormant bacteria from previous infections of the tissue at the implantation site that have been activated from being disturbed during the surgery. The last type, late infection, occurs months to years after the implantation of the implant. Late infections are caused by dormant blood-borne bacteria attached to the implant prior to implantation. The blood-borne bacteria colonize on the implant and eventually get released from it. Depending on the type of material used to make the implant, it may be infused with antibiotics to lower the risk of infections during surgery. However, only certain types of materials can be infused with antibiotics, the use of antibiotic-infused implants runs the risk of rejection by the patient since the patient may develop a sensitivity to the antibiotic, and the antibiotic may not work on the bacteria. [18]

Inflammation, a common occurrence after any surgical procedure, is the body's response to tissue damage as a result of trauma, infection, intrusion of foreign materials, or local cell death, or as a part of an immune response. Inflammation starts with the rapid dilation of local capillaries to supply the local tissue with blood. The inflow of blood causes the tissue to become swollen and may cause cell death. The excess blood, or edema, can activate pain receptors at the tissue. The site of the inflammation becomes warm from local disturbances of fluid flow and the increased cellular activity to repair the tissue or remove debris from the site. [18]

Implant-induced coagulation is similar to the coagulation process done within the body to prevent blood loss from damaged blood vessels. However, the coagulation process is triggered from proteins that become attached to the implant surface and lose their shapes. When this occurs, the protein changes conformation and different activation sites become exposed, which may trigger an immune system response where the body attempts to attack the implant to remove the foreign material. The trigger of the immune system response can be accompanied by inflammation. The immune system response may lead to chronic inflammation where the implant is rejected and has to be removed from the body. The immune system may encapsulate the implant as an attempt to remove the foreign material from the site of the tissue by encapsulating the implant in fibrinogen and platelets. The encapsulation of the implant can lead to further complications, since the thick layers of fibrous encapsulation may prevent the implant from performing the desired functions. Bacteria may attack the fibrous encapsulation and become embedded into the fibers. Since the layers of fibers are thick, antibiotics may not be able to reach the bacteria and the bacteria may grow and infect the surrounding tissue. In order to remove the bacteria, the implant would have to be removed. Lastly, the immune system may accept the presence of the implant and repair and remodel the surrounding tissue. Similar responses occur when the body initiates an allergic foreign body response. In the case of an allergic foreign body response, the implant would have to be removed. [19]

Failures

The many examples of implant failure include rupture of silicone breast implants, hip replacement joints, and artificial heart valves, such as the Bjork–Shiley valve, all of which have caused FDA intervention. The consequences of implant failure depend on the nature of the implant and its position in the body. Thus, heart valve failure is likely to threaten the life of the individual, while breast implant or hip joint failure is less likely to be life-threatening. [1] [19] [20]

Devices implanted directly in the grey matter of the brain produce the highest quality signals, but are prone to scar-tissue build-up, causing the signal to become weaker, or even non-existent, as the body reacts to a foreign object in the brain. [21]

In 2018, Implant files, an investigation made by ICIJ revealed that medical devices that are unsafe and have not been adequately tested were implanted in patients' bodies. In United Kingdom, Prof Derek Alderson, president of the Royal College of Surgeons, concludes: "All implantable devices should be registered and tracked to monitor efficacy and patient safety in the long-term." [22]

See also

Related Research Articles

Endocarditis endocardium disease characterized by inflammation of the endocardium of the heart chambers and valves

Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the surfaces of intracardiac devices. Endocarditis is characterized by lesions, known as vegetations, which is a mass of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells. In the subacute form of infective endocarditis, the vegetation may also include a center of granulomatous tissue, which may fibrose or calcify.

Bacteremia is the presence of bacteria in the blood. Blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal. It is distinct from sepsis, which is the host response to the bacteria.

Phalloplasty is the construction or reconstruction of a penis, or the artificial modification of the penis by surgery. The term phalloplasty is also occasionally used to refer to penis enlargement.

Septic arthritis arthritis that involves infection by a pathogen located in joint

Septic arthritis, also known as joint infection or infectious arthritis, is the invasion of a joint by an infectious agent resulting in joint inflammation. Symptoms typically include redness, heat, and pain in a single joint associated with a decreased ability to move the joint. Onset is usually rapid. Other symptoms may include fever, weakness, and headache. Occasionally, more than one joint may be involved.

Infective endocarditis endocarditis that is characterized by inflammation of the endocardium caused by infectious agents.

Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications may include valvular insufficiency, heart failure, stroke, and kidney failure.

Hip replacement surgery replacing hip joint with prosthetic implant

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Such joint replacement orthopaedic surgery is generally conducted to relieve arthritis pain or in some hip fractures. A total hip replacement consists of replacing both the acetabulum and the femoral head while hemiarthroplasty generally only replaces the femoral head. Hip replacement is currently one of the most common orthopaedic operations, though patient satisfaction short- and long-term varies widely. Approximately 58% of total hip replacements are estimated to last 25 years. The average cost of a total hip replacement in 2012 was $40,364 in the United States, and about $7,700 to $12,000 in most European countries.

Aspiration pneumonia bronchopneumonia that develops due to the entrance of foreign materials into the lungs usually oral or gastric contents

Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may include lung abscess. Some include chemical pneumonitis as a subtype, which occurs from acidic but non-infectious stomach contents entering the lungs.

An artificial heart valve is a device implanted in the heart of a patient with valvular heart disease. When one of the four heart valves malfunctions, the medical choice may be to replace the natural valve with an artificial valve. This requires open-heart surgery. Heart valves are integral to the normal physiological functioning of the human heart. Natural heart valves induce unidirectional blood flow through the valve structure from one chamber of the heart to another. Natural heart valves become dysfunctional for a variety of pathological causes, some of which may require complete surgical replacement of the natural heart valve with an artificial valve.

Joint replacement orthopedic surgery to replace a joint

Replacement arthroplasty, or joint replacement surgery, is a procedure of orthopedic surgery in which an arthritic or dysfunctional joint surface is replaced with an orthopedic prosthesis. Joint replacement is considered as a treatment when severe joint pain or dysfunction is not alleviated by less-invasive therapies. It is a form of arthroplasty, and is often indicated from various joint diseases, including osteoarthritis and rheumatoid arthritis.

Bone-anchored hearing aid type of hearing aid based on bone conduction

A bone-anchored hearing aid (BAHA) or bone-anchored hearing device, is a type of hearing aid based on bone conduction. It is primarily suited for people who have conductive hearing losses, unilateral hearing loss, single-sided deafness and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids. They are more expensive than conventional hearing aids, and their placement involves invasive surgery which carries a risk of complications, although when complications do occur, they are usually minor.

Ventricular assist device

A ventricular assist device (VAD) is an electromechanical device for assisting cardiac circulation, which is used either to partially or to completely replace the function of a failing heart. The function of VADs is different from that of artificial cardiac pacemakers; some are for short-term use, typically for patients recovering from myocardial infarction and for patients recovering from cardiac surgery; some are for long-term use, typically for patients suffering from advanced heart failure.

Breast implant Plastic surgery

A breast implant is a prosthesis used to change the size, shape, and contour of a person's breast. In reconstructive plastic surgery, breast implants can be placed to restore a natural looking breast mound for post–mastectomy breast reconstruction patients or to correct congenital defects and deformities of the chest wall. They are also used cosmetically to enhance or enlarge the appearance of the breast through breast augmentation surgery.

A penile prosthesis, or penile implant, is a medical device which is surgically implanted within the corpora cavernosa of the penis during a surgical procedure. The device is indicated for use in men with organic or treatment-resistant impotence or erectile dysfunction that is the result of various physical conditions such as cardiovascular disease, diabetes, pelvic trauma, Peyronie's disease, or as the result of prostate cancer treatments. Less commonly, a penile prosthesis may also be used in the final stage of plastic surgery phalloplasty to complete female to male gender reassignment surgery as well as during total phalloplasty for adult and child patients that need male genital modification.

Port (medical) small medical appliance that is installed beneath the skin

In medicine, a port is a small medical appliance that is installed beneath the skin. A catheter connects the port to a vein. Under the skin, the port has a septum through which drugs can be injected and blood samples can be drawn many times, usually with less discomfort for the patient than a more typical "needle stick".

Cerebritis is an infection of the brain that normally leads to the formation of an abscess within the brain itself. It is the inflammation of the cerebrum, a structure within the brain, which performs a number of important functions, including most of the things which people associate with being human, such as memory and speech. It is also defined as a purulent nonencapsulated parenchymal infection of brain which is characterized by nonspecific features on CT and cannot reliably be distinguished from neoplasms.

Meningitis inflammation of membranes around the brain and spinal cord

Meningitis is an acute inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or altered consciousness, vomiting, and an inability to tolerate light or loud noises. Young children often exhibit only nonspecific symptoms, such as irritability, drowsiness, or poor feeding. If a rash is present, it may indicate a particular cause of meningitis; for instance, meningitis caused by meningococcal bacteria may be accompanied by a characteristic rash.

Sophoraflavanone G chemical compound

Sophoraflavanone G is a volatile phytoncide, released into the atmosphere, soil and ground water, by members of the Sophora genus. Due to an increase in the rates of antibiotic-resistant bacteria, scientific efforts have focused on finding either naturally-made or genetically modified compounds that can treat and or prevent these harmful and sometimes deadly bacteria. Sophoraflavanone G, due to its use as a phytoncide, has been found to impact the growth of antibiotic-resistant bacteria and enhance the effect of currently used antibiotics.

Surgical mesh

Surgical mesh is a loosely woven sheet which is used as either a permanent or temporary support for organs and other tissues during surgery. Surgical mesh is created from both inorganic and biological materials and is used in a variety of surgeries. Though hernia repair surgery is the most common application, it can also be used for reconstructive work, such as in pelvic organ prolapse.

Implant failure refers to the failure of any medical implant to meet the claims of its manufacturer or the health care provider which installs it. Implant failure can have any number of causes. The rates of failure vary for different implants.

Postoperative wounds are those wounds acquired during surgical procedures. Postoperative wound healing occurs after surgery and normally follows distinct bodily reactions: the inflammatory response, the proliferation of cellular and tissues that initiate healing, and the final remodeling. Postoperative wounds are different from other wounds in that they are anticipated and treatment is usually standardized depending on the type of surgery performed. Since the wounds are 'predicted' actions can be taken beforehand and after surgery that can reduce complications and promote healing.

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