page_title: Prosthesis
section_title: Current technology and manufacturing
hierarchical_section_title: Prosthesis / Current technology and manufacturing
caption_attribution_description: English: Shows the moulding process used to create a prosthetic finger. Original caption: Figure 4. The prosthetic finger. (A) The moulds of the patient's reconstructed bone, which was accurately positioned using the fins. (B) The reconstructed finger after the silicone's curing process. Citation: Cabibihan J-J (2011) Patient-Specific Prosthetic Fingers by Remote Collaboration–A Case Study. PLoS ONE 6(5): e19508. doi:10.1371/journal.pone.0019508 Editor: Alejandro Almarza, University of Pittsburgh, United States of America Received: January 10, 2011; Accepted: March 30, 2011; Published: May 4, 2011 Copyright: © 2011 John-John Cabibihan. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by the Academic Research Fund Tier 1, Ministry of Education, Singapore under the project R-263-000-506-133. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The author has declared that no competing interests exist. E-mail: elecjj@nus.edu.sg
context_page_description: In medicine, a prosthesis or prosthetic implant is an artificial device that replaces a missing body part, which may be lost through trauma, disease, or a condition present at birth. Prostheses are intended to restore the normal functions of the missing body part. Amputee rehabilitation is primarily coordinated by a physiatrist as part of an inter-disciplinary team consisting of physiatrists, prosthetists, nurses, physical therapists, and occupational therapists. Prostheses can be created by hand or with computer-aided design, a software interface that helps creators design and analyze the creation with computer-generated 2-D and 3-D graphics as well as analysis and optimization tools.
context_section_description: Over the years, there have been advancements 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 extra energy necessary 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 to trans-radial and transhumeral amputees because they are more likely to have the artificial limb exposed.
  In addition to new materials, the use of electronics has become very common in artificial limbs. Myoelectric limbs, which control the limbs by converting muscle movements to electrical signals, have become much more common than cable operated limbs. Myoelectric signals are picked up by electrodes, the signal gets integrated and once it exceeds a certain threshold, the prosthetic limb control signal is triggered which is why inherently, all myoelectric controls lag. Conversely, cable control is immediate and physical, and through that offers a certain degree of direct force feedback that myoelectric control does not. Computers are also used extensively in the manufacturing 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 (stump) of the amputee by belts and cuffs or by suction. The residual limb either directly fits into a socket on the prosthetic, or—more commonly today—a liner is used that then is fixed to the socket either by vacuum (suction sockets) or a pin lock. Liners are soft and by that, they can create a far better suction fit than hard sockets. Silicone liners can be obtained in standard sizes, mostly with a circular (round) cross section, but for any other residual limb shape, custom liners can be made. The socket is custom made to fit the residual limb and to distribute the forces of the artificial limb across the area of the residual limb (rather than just one small spot), which helps reduce wear on the residual limb. The custom socket is created by taking a plaster cast of the residual limb or, more commonly today, of the liner worn over the residual limb, and then making a mold from the plaster cast. Newer methods include laser-guided measuring which can be input directly to a computer allowing for a more sophisticated design.
  One problem with the residual limb and socket attachment is that a bad fit will reduce the area of contact between the residual limb and socket or liner, and increase pockets between residual limb skin and socket or liner. Pressure then is higher, which can be painful. Air pockets can allow sweat to accumulate that can soften the skin. Ultimately, this is a frequent cause for itchy skin rashes. Over time, this can lead to breakdown of the skin.
  Artificial limbs are typically manufactured using the following steps:
  Measurement of the residual limb
  Measurement of the body to determine the size required for the artificial limb
  Fitting of a silicone liner
  Creation of a model of the liner worn over the residual limb
  Formation of thermoplastic sheet around the model – This is then used to test the fit of the prosthetic
  Formation of permanent socket
  Formation of plastic parts of the artificial limb – Different methods are used, including vacuum forming and injection molding
  Creation of metal parts of the artificial limb using die casting
  Assembly of entire limb
caption: Manufacturing a prosthetic finger
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