Merck Manual

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Fitting the Prosthesis


Jan J. Stokosa

, CP, American Prosthetics Institute, Ltd

Reviewed/Revised Jan 2021 | Modified Sep 2022
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A prosthesis has 7 basic component parts:

  • Residual-limb gel cushion interface: A silicone gel or viscoelastic material that protects the skin and modulates pressure

  • Suspension system: Connects the prosthesis to the body

  • Socket: Rigid plastic receptacle into which the residual limb with gel interface is inserted (there may be an inner primary flexible socket that helps modulate forces)

  • Joints (ankle, knee, wrist, elbow) and terminal appendage (hand, foot)

  • Modular endoskeletal system connection couplings: Connect prosthetic joints and terminal appendages and provide adjustability

  • Anatomic shape: Soft foam material that simulates muscle contours and protects endoskeletal components

  • Synthetic skin: Thin, tone-matching layer applied over the anatomic shape

During the fitting process, an impression of the residual limb is made either by hand-applied plaster bandages or digital imaging. Then a positive model of the limb is made either by hand from plaster or digitally and used to fabricate a socket by hand or using a computer-controlled milling machine. A socket is formed around the positive model. This socket is integrated into a diagnostic prosthesis that will test various component combinations to determine which option provides optimal stability, function, and biokinematic efficiency. Once components and design have been selected, the definitive socket is fabricated, usually of carbon fiber and other durable materials, and the definitive prosthesis is aligned and optimized. The external appearance is created, either an anatomically realistic one symmetric to the opposite limb or one that leaves the components exposed. The fitting process takes 7 to 18 visits, depending on complexity, and about 16 laboratory fabrication procedures.

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NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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