A prosthesis is a replacement of an organ or limb with products that function similarly and are artificially created.
What is a prosthesis?
The first prostheses existed as early as the 20th century BC, found in Egypt. Then, in the Middle Ages, the so-called iron hands were created, whose principle of construction was maintained until the 18th century. The first movable arm prostheses were an invention of the dentist Peter Baliff and Margarethe Caroline Eichler respectively. Today, microprocessor-controlled leg or arm prostheses can be used to perform very complex movements and it is also possible to engage in sports with them.
Shapes, types and styles
A below-knee prosthesis is a leg prosthesis that is used after an amputation of the leg below the knee joint. If the prosthesis is found outside the human body, it is called an exoprosthesis. This includes, for example, hand, arm or leg prostheses. Lower limb prostheses are divided into: Foot prostheses, lower leg prostheses and thigh prostheses that are used after amputations, as well as whole leg prostheses for hemipelvectomies or hip disarticulations. Upper extremity prostheses are divided into forearm or upper arm prostheses. A closed implant is called an endoprosthesis. This is completely surrounded by tissue, a typical example being the artificial hip joint. Endoprostheses partially or completely replace a joint and remain in the body permanently. However, endoprostheses also include vascular replacements, heart valve replacements, and breast implants. An endoprosthesis is precisely fitted into the bone bed, whereby a distinction can be made between cemented prostheses, hybrid prostheses and cementless prostheses. If signs of wear occur in the glenoid cavity or the humeral head, a part can be replaced, in which case it is referred to as a hemiprosthesis. This contrasts with the full prosthesis or “total shoulder”, in which the glenoid and humeral head are replaced. Another form of shoulder prosthesis is the so-called surface replacement, which is also called cup prosthesis. A so-called open implant is anchored in a bone, but is also visible outside. These include dental implants or implants used to attach prosthetic legs or imitation ears. Dental prostheses also come in a wide variety. They are removable, although there are also combinations that are partly fixed and partly removable. Removable dentures include full or complete dentures or model cast dentures.
Structure and mode of operation
Arm prostheses that have a gripping function are mostly made of PVC, a material that is very durable and has a greater resemblance to the skin than, for example, leather or wood. One negative effect of PVC outer skins is that they get dirty relatively easily, because after about three to four months the plastic discolors and then needs to be changed. As an alternative, cosmetic gloves made of silicone are also offered, which do not discolor and are also dirt-repellent. However, they run the risk of tearing. In addition, they are much more expensive and their abrasion is also very strong. Furthermore, silicone gloves are also available, which are infused with nylon. These have a durability of about six months, but cost significantly more than gloves made of PVC. For leg prostheses, ground foam is often used, which is covered with a cosmetic stocking. A knee prosthesis is used to replace the worn joint portion of a knee joint. A knee prosthesis consists of at least two different parts: a tibial part and a femoral part. The femoral component is usually made of a cobalt-chromium alloy, while the tibial component is made of a metal component with a plastic overlay. Very hard plastic is taken for the patellar portion, but replacement of this back surface is not mandatory, while the other two components must be replaced regularly. However, the everyday life of the respective patient must also be taken into account, as the prosthesis is exposed to different loads. Lower limb prostheses are divided into: Foot prostheses, lower leg prostheses and thigh prostheses.A prosthesis stem for an upper or lower limb replacement is always individually manufactured, usually using a plaster cast as the basis. The stem of a hip prosthesis is normally made of titanium alloys, CoCrMo forging alloys and, in individual cases, fiber-reinforced plastics. In the case of shoulder prostheses, on the other hand, it is very important that the different size and angle relationships of the glenoid cavity and humeral head are precisely restored. In the case of dentures, model cast dentures are composed of plastic components or a metal framework. This type of prosthesis is relatively inexpensive and also gentle on the teeth, since the remaining teeth do not have to be ground down. However, an aesthetic disadvantage is that the clasps are often visible. These partial dentures can also be extended and they are also suitable for people for whom further tooth loss is foreseeable. Patients who no longer have any teeth receive a complete denture. This consists of a plastic base into which the plastic teeth are then inserted. The biggest problem with these dentures is adhesion. Upper dentures usually adhere better because they have a larger contact surface, while the contact surface in the lower jaw is smaller and this type of denture is also less stable. In many cases, adhesion is improved by using a denture adhesive.
Medical and health benefits
Prostheses are used to replace body parts that no longer fulfill their function for a wide variety of reasons, allowing users to maintain their independence as much as possible. Initially, prostheses were only very primitive aids, but in recent years they have become extremely powerful, so that, for example, sports can also be practiced with prosthetic legs. Dental prostheses are now also made to such a high standard that often no difference is noticed between them and real teeth, and the perfect fit also guarantees the highest possible wearing comfort.
