Senior Science Bionics Part 1: Biomedical & Biomaterial Devices

1 Identify parts of the body and the biomaterials and biomedical devices that can be used to replace damaged or diseased body parts including – pins, screws and plates – artificial joints – pacemakers – artificial valves – crowns, dentures – lenses – prosthetic limbs – cochlear implants

Biomaterials Biomaterial is a substance used in a medical device intended to interact with biological systems. Some biomaterials are intended to last for as long as possible. Other biomaterials are made to last a short time it is intended that the body dissolve or remove them in some way. Thus sutures (stitches) naturally dissolve over time so they don't need to be removed, while bone plates are incorporated into normal bone.

Biomaterials A wide range of biomaterials have been found suitable for use within humans. Metals must be corrosion-resistant so that alloys such as stainless steel and newer 'superalloys' are mostly used. They are required where strength is needed, such as in hip replacements. Plastics have to sometimes withstand considerable forces. For this reason UHMWPE, a form of polyethylene, is often used. Teflon and dacron can be used for fabrics, while other plastics have to act as a glue. Some plastics are designed to be degraded and absorbed by the body after they have served their function. Ceramics are used with bones while others are tooth replacements. They are very strong when compressed, but they are brittle. Biological tissue is used during transplants, especially with heart valves.

Pins, Screws and plates These are used to repair bone fractures. They are almost all made from metallic alloys such as titanium / cobalt / chromium / molybdenum or stainless steel. The pin is a versatile implant used for the fixation of bone fragments and is used when the fracture is in a place where it is difficult to use a plate. Pins are also used when it is difficult to obtain adequate stability of the bone fracture by any other means.

Pins, Screws and plates Screws are some of the most widely used devices for repairing fractures. They are used to fix bone plates to bones. Bone plates are also used to repair bone fractures. They are designed to be very strong and absorb the large stress forces generated when the bone moves. It is also important that the bone plate be fixed to the bone with the use of screws.

Artificial Joints These replace joints that have been largely destroyed by degenerative diseases such as arthritis or damaged badly in an accident. Common examples are knee, hip and shoulder joints; the latter two are ball and socket type joints.

Artificial Joints Artificial knee joints are known to sink into the lower bone of the leg, causing crushing of thetrabecular bone. To combat this problem, knee joints are now made from a layer of ultra-high molecular weight polyethylene (UHMW polyethylene) on a metal base. Other joint replacements, such as fingers and ankles, have not been as successful, because of the complexity of movement of these joints.

Artificial Joints Artificial hip joints are often made from a stainless steel- polyethylene or cobalt- chromium alloy-polyethylene combination. Other materials that can be used are: titanium titanium-aluminium-vanadium alloy ultra high molecular weight polyethylene metal-pyrolytic carbon coating metal-bioglass coating composites made from poly-methyl methacrylate (PMMA) and carbon fibre porous stainless steel.

Pacemakers To help the heart beat in a regular rhythm. Attached to the battery are two electrodes that connect it with the heart. Under local anaesthesia, the pacemaker is implanted under the skin of the chest wall, and the electrodes are threaded through a vein near the collarbone and guided to the heart muscle. The artificial cardiac pacemaker regulates heartbeats by sending electrical impulses to the heart muscle. When the muscle is stimulated, it contracts or beats.

Artificial Valves A heart valve replacement is performed when a diseased valve that cannot be repaired is removed and replaced with a substitute mechanical or biological valve. Mechanical valves are constructed of durable materials such as dacron, teflon, titanium, and pyrolytic carbon; they are very sturdy and can be expected to last a lifetime. Mechanical valves require the long-term use of anticoagulation medication to prevent formation of blood clots on the valve prosthesis. They can also be noisy as they open and close.

Cochlear Implants A cochlear implant, also known as a bionic ear, can markedly improve communication for a severely hearing impaired person.

Cochlear Implants