There are many options for limb prostheses, but after a functional evaluation results in a treatment plan, the fitting process typically follows the same steps regardless of which limb prosthesis is chosen. The steps for fitting the prosthesis are coordinated with physical therapy and occupational therapy training sessions. (See also Overview of Limb Prosthetics.)
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.
Transcutaneous osseointegration, an alternative to a traditional socket prosthesis, involves surgically implanting a prosthetic anchor into the residual limb’s bone, changing the soft tissue interface between the residual limb and the prosthetic socket. This alternative may be especially helpful for patients who previously had a poor experience (including pain, lack of stability, and skin problems) with their socket prosthesis.
