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Prosthesis

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Prosthetic toe, Ancient Egypt
Prosthetic toe, Ancient Egypt
A soldier in the U.S. Army plays foos-ball with two prosthetic limbs. Courtesy of the U.S. Army, by Walter Reed photographers.
A soldier in the U.S. Army plays foos-ball with two prosthetic limbs. Courtesy of the U.S. Army, by Walter Reed photographers.

A prosthesis is a device which replaces a missing body part or limb, which may be due to trauma or congenital defect, to assist or improve function. The cause of amputations is quite different between upper-limb and lower-limb amputations. While lower-limb is primarily caused by peripheral vascular disease, upper-limb amputations are most likely caused by traumatic injury.


Contents

Upper-Extremity Prostheses

The type of prosthesis used depends, in part, on the level of the amputation. Classification of upper-limb amputation is related to the anatomy of an amputated limb.

Digit or partial hand prosthesis

This type of prosthesis is used when an amputation is at a level below the wrist.

Hand prosthesis

The I-limb Ultra
The I-limb Ultra
This type of prosthesis may be used in cases of wrist disarticulation, that is, amputation at the wrist level, including the removal of the radius and ulna to styloid processes. One example is the I-limb Ultra.

Transradial Prostheses

A Transradial prosthesis
A Transradial prosthesis

This type of prosthesis is used for below-elbow (transradial) amputations. The transradial prosthesis typically includes a terminal device, wrist unit, elbow unit, socket and harness. The selection of these components is based on a patient’s functional goals and capabilities.

Transhumeral Prostheses

This type of prosthesis is used for above-elbow (transhumeral) amputations.

Shoulder Disarticulation Prostheses

This type of prosthesis is used when an amputation is at the shoulder level.



Lower-Extremity Prostheses


The level of lower limb amputation determines the type of prosthesis a person will use. Lower-extremity amputation and disarticulation levels include the following (Smith 2004):

  • Partial foot amputation and disarticulation, including toe, ray, transmetatarsal, tarsometatarsal (Lisfranc), and transtarsal (Chopart)
  • Ankle amputation and disarticulation, including Symes, Pirogoff, Boyd, and Boyd-Pirogoff
  • Below the knee (transtibial) amputation
  • Knee disarticulation
  • Above the knee (transfemoral) amputation
  • Hip disarticulation
  • Hemipelvectomy

Partial foot amputation/disarticulation prosthses

Partial foot prostheses include artificial toes, shoe fillers, and cosmetic coverings. If the ankle stability is compromised, the devices may extend out of the shoe and terminate around the ankle or calf. They may be made of foam, plastic, or even metal, depending on the specific person’s needs.

The purpose of these is both cosmetic and biomechanical. A partial foot prosthesis (such as fillers and spacers) may resisting foot deformation over time and improving balance. These will help the foot function better and improve comfort. Cosmetic aids include silicone toe and partial foot caps.

Ankle level amputation/disarticulation

The prostheses for this level of amputation and disarticulation are made from a custom shaped hard socket that covers the residual limb from below the knee to the end of the limb. The socket may be padded with a foam liner, or a gel liner may be rolled over the skin of the residual limb. The bottom of the socket is attached to a prosthetic foot. These devices are often called “low profile” or a “Symes” prostheses.

Below the knee (transtibial) prosthesis

A man with a below the knee (transtibial) prosthesis
A man with a below the knee (transtibial) prosthesis

While the exact construction of the prosthesis will vary, the general parts of a below the knee (transtibial) prosthesis are the socket, pylon, and foot. The socket is molded to the precise shape of the residual limb. The socket is typically made from hard plastic or acrylic resin. Similar to a Symes prostheses, a foam or plastic liner may be placed in the socket or a gel liner may be rolled on the residual limb. The socket is connected to a pylon (which is often an aluminum tube), which is connected to a prosthetic foot. Some people choose to cover the pylon with a custom shaped foam cover, while others prefer to leave it exposed. The prosthetic foot could be made from carbon fiber, metal, foam, and wood. In addition to these parts, suspension of the prosthesis is important. Some was to secure the prosthesis to the residual limb include a tight socket brim, suction, a locking pin, and knee cuffs.

Knee disarticulation and above the knee (transfemoral) prosthesis

A transfemoral prosthesis
A transfemoral prosthesis

The prosthesis for a knee disarticulation or above the knee (transfemoral) amputation is made from a socket, pylon, and foot and artificial knee. The socket, pylon, and foot are similar to those of transtibial prostheses. The knees are monocentric or polycentric depending on how they flew. They have different control mechanisms including hydraulic, pneumatic, and computerized control. In addition to the knee, other components such as a rotator unit may make activities of daily living easier. Standard ways to suspend the socket to the leg include a tight contoured socket (for knee disarticulation), belts, suction, and locking pins.

Hip disarticulation and hemipelvectomy

Hip disarticulation an hemipelvectomy prostheses include all the parts of a transfemoral prosthesis (socket, knee, pylon, and foot) but also includes a hip joint component.


Concluding comments

The optimal experience for someone with an amputation is multi-faceted. A multidiciplinary team- including the patient- is best suited to manage care before surgery, after surgery, during rehabilitation, and through a lifetime. Together they address subjects such as gait assessment, biomechanical analysis, material and technology selection, and activity tolerance. This team may include the patient, the patient’s family, doctors, therapists, and prosthetists (Lusardi 2007). In general, using a prosthesis is easier with better health, a lower amputation level, and a good medical team. However, despite best efforts, prosthetic care does not completely restore normal walking ability (Perry 2010).

Limitations of this article

While this article identifies major types of prostheses, the specific prosthesis used is customized for each patient. Patient, caregiver, and device factors leads to a specific prosthesis. Patient factors include: goals, abilities, and future abilities. Device factors include cosmesis, cost, function, safety, and comfort. Finally, caregiver factors include the knowledge, determination, skill, and ability to provide the best prosthesis available for a specific individual.


References

  • Lusardi, M., Nielsen, C. Orthotics and Prosthetics in Rehabilitation, 2nd ed. Saunders, Elsevier, 2007.
  • Perry, J., Burnfield, J. Gait Analysis, Normal and Pathological Function, 2nd ed. Slack Inc., 2010.
  • Smith, D., Michael, J., Bowker, J. Atlas of Amputations and Limb Deficiencis, Surgical, Prosthetic, and Rehabilitation Principles. 3rd ed. American Academy of Orthopaedic Surgeons, 2004.

External links


Author: Weerawat Limroongreungrat, Daniel Marler
Affiliation: Division of Physical Therapy, Georgia State University, The Georgia Institute of Technology
Email Address: weerawatl@gmail.com, marler.daniel@gmail.com