Why are plastics and alloys useful in the replacement of human body parts?

Answer 1

The materials used in artificial joints vary, depending on the type of joint being replaced and how the joint needs to function. Hip joints, for example, need to be sturdy and able to bear your body's weight. Knee joints need to be flexible as well as strong, while finger joints must be capable of bending easily. In general, the components must be durable, flexible and able to function in the body without causing an immune system reaction.

Artificial joints have improved greatly since they were first introduced around 40 years ago. Replacements for hip and knee joints include portions made from metal, such as stainless steel, titanium or chrome and cobalt alloys. Other potions are made of a strong, durable plastic called polyethylene.

There are new types of knee replacement parts that are highly flexible, allowing the knee to bend up to 155 degrees. Not all people qualify for such a component; ask your surgeon. The pieces are designed to fit perfectly together and to function as closely as possible to a natural joint. Special bone cement is used in some cases to hold static parts of the artificial joint in place.

Some new implants are made of a special type of ceramic material or oxidized zirconium. A ceramic implant has a smooth surface that reduces the friction and wear on the joint that can result in the need for revision surgery. Ceramic implants are used primarily for hip replacements, as the material is too fragile to withstand the extensive weight and activity placed on the knees.

The zirconium implants are made of metal that has gone through a process that allows oxygen to absorb into the metal, creating a ceramic surface. These implants incorporate the benefits of a smooth surface with the benefits of a hard material, making it an ideal option for both hips and knees. While traditional implants last about 15 years, those made of these newer materials potentially can last up to 20 or 25 years. Another benefit of these new materials is that people who are allergic to metals can still use them.

Traditionally, replacement parts for finger joints have been made from silicone, in order to allow the flexibility required of fingers. However, this type of replacement has tended to slip somewhat because it does not fit tightly into the bones of the fingers. Researchers are working on new types of finger implants that are more like those used for knees and hips. These implants, like those for knees and hips, are made of metal and plastic materials that fit into the bones and more closely resemble a regular human joint. Researchers are still testing and perfecting finger replacements made of metal and plastic.

Answer 2

Plastics and alloys are useful in the replacement of human body parts due to their unique properties. Plastics, such as polyethylene and polypropylene, are lightweight, durable, and biocompatible, making them suitable for prosthetics and implants. Alloys, like titanium and cobalt-chrome, possess high strength, corrosion resistance, and good biocompatibility, making them ideal for orthopedic implants like joint replacements. These materials can provide stability and functionality to replace damaged or missing body parts.