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* This is the Professional Version. *

Options for Limb Prostheses

By James Baird,

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Patient Education

The prosthetist explains the available options and helps users choose the type of prosthesis and options they need to accomplish their goals. For example, women who want to wear shoes with different heel heights may prefer a prosthetic ankle that can adjust to different heights. Swimmers can get a 2nd prosthetic leg that is designed for swimming and can withstand water, salt, and sand. Runners can get prosthetic feet specifically designed for running.

Hand Prostheses

Options for hand prostheses include

  • Precision (pincher) grip

  • Tripod (palmar) grip

  • Lateral (key pinch)

  • Hook

  • Spherical

  • Sport-specific

  • Myoelectric

Hand prostheses with precision (pincher) and tripod (palmar) grips

These grips enable the user to pick up or pinch a small object. A hand prosthesis with a precision grip has a thumb that opposes the pad of the index finger; a hand prosthesis with a tripod grip has a thumb that opposes the pads of the index and middle fingers.

Lateral hand prosthesis

A lateral hand prosthesis enables the user to manipulate a small object (eg, turning a key in a lock) because it has a thumb that opposes the side of the index finger.

Hook prosthesis

A hook prosthesis enables the user to carry objects with a handle. It allows for thumb and finger flexion. A myoelectric hook improves the line of sight for functional grasp.

Spherical hand prosthesis

A spherical prosthesis allows thumb and fingertip flexion. A user with this type of prosthesis can grasp a round object (eg, door knob, electric bulb).

Sport-specific hand prosthesis

Sport-specific prostheses can include a hand with a gripping device (eg, for golf, archery, or weight-lifting) or a hand with a mesh pocket for catching a baseball.

Myoelectric functional hand prosthesis

New developments in small, wireless electronic devices that control movement and sensation in a patient's prosthetic hand introduce features that can help provide a more natural grip.

Elbow Prostheses

Options for elbow prostheses include

  • Body-operated

  • Friction-operated

  • Myoelectric

Body-operated elbow prosthesis

A body-operated prosthesis consists of a cable and harness that uses shoulder and back movement to move the arm. Although body-operated elbow prostheses are lightweight, they are less attractive than other options and are sometimes bothersome to the user.

Friction-operated elbow prosthesis

A friction-operated prosthesis is raised or lowered by using the hand of the other arm. It is lightweight.

Myoelectric elbow prosthesis

Myoelectric prostheses require no cables and provide more function. However, they are heavy.

Foot Prostheses

Options for foot prostheses include

  • Solid ankle, cushioned heel

  • Single-axis design

  • Multiple-axis (multiaxial) design

  • Stored-energy (dynamic response) design

  • Sport-specific

Solid ankle, cushioned heel (SACH) foot prosthesis

This type of prosthesis consists of a basic immovable foot made of rubber and wood. Stability is provided for the knee when the heel touches the ground because its soft heel allows the whole foot to contact the ground. However, less stability is provided when the user raises the heel and the opposite leg swings forward, resulting in uneven walking. A SACH prosthesis requires more energy to use than other types of prosthetic feet. It is appropriate for people who are limited in their activities and is not a good choice for active people.

Foot prosthesis with single-axis design

A prosthesis with single-axis design has an ankle joint that allows dorsiflexion and plantarflexion of the foot. This design allows the whole foot to quickly contact the ground after the heel touches the ground and for the knee to straighten quickly. Because of these features, the prosthesis provides good stability for the knee, which is particularly important for people with above-the-knee amputation. Single-axis design prostheses are not appropriate for active people.

Foot prosthesis with multiple-axis (multiaxial) design

A foot prosthesis with multiaxial design has an ankle joint that allows dorsiflexion and plantarflexion of the foot and inversion, eversion, and rotation of the ankle. This design enables users to walk on uneven terrain more easily and is thus appropriate for active people. With newer, lightweight models, minimal maintenance is required. The prosthesis can be made to look lifelike.

Foot prosthesis with stored-energy (dynamic response) design

A foot prosthesis with stored-energy design is made of carbon graphite, which is lightweight and strong. It requires less energy to use because the foot stores energy from when the heel touches the ground to when the toes push off, propelling the user forward. The design may include a shock absorber to reduce the force of contact with the ground during walking. Users are able to walk smoothly and relatively naturally. This type of foot prosthetic is appropriate for active people.

Sport-specific foot prosthesis

Foot prostheses can be customized for a specific sport. For example, for runners (long-distance and sprinting), the prosthesis is designed with the foot bent downward toward the sole and with the capacity to store energy needed to propel the user forward. For swimmers, the prosthesis is designed with an ankle that allows full range of motion in water.

Knee Prostheses

Options for knee prostheses include

  • Single-axis, constant friction design

  • Polycentric design

  • Weight-activated stance control feature

  • Manual lock feature

  • Fluid control system

  • Microprocessor feature

Knee prosthesis with single-axis, constant friction design

A prosthetic knee with single-axis, constant friction design has only one pivot point (the knee bends like a hinge). The design is simple, and the prosthesis is durable, lightweight, and inexpensive. The prosthesis uses friction that does not vary to control the leg when it swings forward. Users can walk normally at only one speed. The prosthesis relies on correct alignment by the prosthetist and muscle control by the user to provide stability.

Knee prosthesis with polycentric design

This type of knee prosthesis has several hinges with several pivot points that change as the knee moves, providing increased stability. The prosthesis shortens slightly when the knee is bent, so that the toe clears the ground more easily when the leg swings forward. The polycentric design of this type of prosthesis provides stability for people with a short residual limb and is appropriate for people whose leg has been amputated at the knee joint, enabling users to sit more comfortably without the knee protruding.

Knee prosthesis with weight-activated stance control feature

A prosthesis with weight-activated stance control feature locks the knee in a slightly bent position (to provide braking) when weight is put on the foot. Constant friction is used to control the leg when it swings forward, but the prosthesis has a knee extension aid, which helps swing the leg. Users can walk at only one speed. The prosthesis is appropriate for people with weak muscles.

Knee prosthesis with manual lock feature

A knee prosthesis with manual lock feature can be locked or unlocked by users as needed but requires a cable to do so. Although this type of prosthesis provides the most stability, it requires more energy to use than other types of prosthetic knees. Because the prosthesis does not provide swing-phase flexion, walking is stiff and awkward and is the least desirable choice.

Knee prosthesis with fluid control system

Knee prostheses with fluid control system may use compressed air (pneumatic system) or fluid (hydraulic system) to produce, store, and release energy as the knee bends and straightens. This type of prosthetic knee enables users to walk at different speeds and is the best choice for most people. It may be equipped with a microprocessor.

Knee prosthesis with microprocessor feature

Knee prostheses with microprocessor feature have sensors that detect movement and can adjust the hydraulic fluid or the magnetorheological fluid control system accordingly. The prosthetic knee provides good control when the foot is on the ground and when the leg swings forward. It can be programmed to compensate for stumbling and to enable users to descend stairs and ramps. Less energy is needed to use the prosthesis, and allow the user to achieve a more natural gait than would otherwise be possible.

* This is the Professional Version. *