In medicine, a prosthesis is an artificial device that replaces a missing part of the body, which can be lost due to trauma, disease or congenital conditions. The prostheses are intended to restore the normal functions of the missing body part.
The rehabilitation of prosthetic amputees is coordinated mainly by a prosthetist and an interdisciplinary team of health professionals that include psychiatrists, surgeons, physiotherapists and occupational therapists. Prostheses are commonly created with CAD, a software interface that helps creators visualize creation in 3D form. But they can also be designed by hand.
Current technology and manufacturing
Over the years, there have been advances in artificial limbs. New plastics and other materials, such as carbon fiber, have allowed artificial limbs to be stronger and lighter, limiting the amount of additional energy needed to operate the limb.
This is especially important for trans-femoral amputees. Additional materials have allowed artificial limbs to look much more realistic, which is important for trans-radial and trans-humeral amputees because they are more likely to have the artificial limb exposed.
In addition to the new materials, the use of electronics has become very common in artificial limbs. The myoelectric limbs, which control the limbs by converting muscle movements into electrical signals, have become much more common than limbs driven by cable.
The myoelectric signals are picked up by the electrodes, the signal is integrated and once it exceeds a certain threshold, the prosthetic control signal of the limb is activated, which is why, inherently, all the myoelectric controls are delayed. On the contrary, the control of the cable is immediate and physical, and for that reason it offers a certain degree of feedback of the direct force that the myoelectric control does not.
Computers are also widely used in the manufacture of limbs. Computer-aided design and computer-aided manufacturing are often used to assist in the design and manufacture of artificial limbs.
Most modern artificial limbs are attached to the residual limb of the amputee by means of belts and cuffs or by suction. The residual limb fits directly into a socket of the prosthesis or, more commonly today, a liner is used which is then fixed to the socket by vacuum or a plug lock.
The coatings are soft and therefore, they can create a suction fit much better than hard plugs.
Silicone coatings can be obtained in standard sizes, mainly with a circular cross section, but for any other form of residual limb, custom coatings can be made.
The socket is tailored to fit the residual limb and to distribute the forces of the artificial limb along the area of the residual limb, which helps reduce wear on the residual limb.
The custom fit is created by taking a plaster cast of the residual limb or, more commonly nowadays, of the lining used on the residual limb, and then making a cast from the plaster. Newer methods include laser guided measurement that can be entered directly into a computer, allowing a more sophisticated design.