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* This is the Consumer Version. *

Options for Limb Prostheses

By James Baird, CPO, Hanger Clinic

A prosthetist is an expert who designs, fits, builds, and adjusts prostheses. The prosthetist explains the available options and helps people choose the type of prosthesis and the options they need to accomplish their goals. For example, women who want to be able to wear shoes with different heel heights may prefer a prosthetic ankle that can adjust to different heights. People who swim can get a second 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) or tripod (palmar) grip

A hand prosthesis with a precision grip has a thumb that opposes (presses against) 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. Having a prosthesis with either a precision or a tripod grip enables the person to pick up or pinch a small object.

Lateral hand prosthesis

A lateral hand prosthesis enables the person to manipulate a small object (for example, 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 person 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 person using this type of prosthesis can grasp a round object (such as a door knob or electric bulb).

Sport-specific hand prosthesis

Sport-specific prostheses can include a hand with a gripping device (for example, 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 person's prosthetic hand allow for 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 can be 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 person 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 the foot to flex up or down. 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 the foot to flex up or down and for the ankle to rotate or move to face inward or outward. 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 person forward. The design may include a shock absorber to reduce the force of contact with the ground during walking. A person who uses this type of prosthesis is able to walk smoothly and relatively naturally. This type of foot prosthesis 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 person 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. People 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 also 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. A person who uses this type of prosthesis 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 has somewhat limited movement during walking, walking is stiff and awkward, making this the least desirable choice.

Knee prosthesis with fluid control system

Knee prostheses with fluid control system may use compressed air (a pneumatic system) or fluid (an 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. 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. The user achieves a more natural gait than would otherwise be possible.

Types of prostheses.

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* This is the Consumer Version. *