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Prosthetic Limbs: The Major Types

Date: Jan 15, 2023
Tags: prosthetic, arm, leg, prosthesis, machine, electrode, muscle, impulse
 

What are prosthetic limbs?

Prosthetic limbs are artificial limbs that allow those with amputated limbs to move around easily. Prosthetic arms and legs are the most widely used prosthetics and about 95% of people with prosthetics have claimed that it is extremely useful.

There are many variations of prosthetic arms and legs. Some prostheses are designed to be visually appealing. These prostheses mimic the look of natural limbs and have a synthetic skin covering. If you want, you can even get prostheses with details such as freckles, fingerprints, and paint-able nails. Other prostheses are designed to be more functional. These prostheses are made of lightweight materials and are primarily helpful for sports and more physical activities, but they usually don't have a synthetic skin covering, so metal is visible. Additionally, these types of prostheses are cheaper than cosmetic prostheses. Prostheses can also include appendages such as fingers on the hand. In advanced prostheses, these appendages can be controlled by flexing arm muscles, but in others, they are simply cosmetic. For those who prefer function over form, some prostheses have hooks, grips, or web-like tools for specialized purposes.

Types of prostheses

There are two main types of prostheses:
  • Exoskeletal prostheses have a hard metal or plastic shell, are permanently fixed, and are not adjustable. These prostheses are for people who are physically active or are routinely in situations that could damage a soft prothesis.
  • Endoskeletal prostheses are adjustable, but that leads to a reduced durability factor. The prosthesis is usually covered by soft foam to give the appearance of a natural limb.

Upper Limb Prostheses

First, we'll talk about prosthetic arms.

There are 5 main types of upper limb prostheses:

  • Passive prostheses look like natural limbs and are the cheapest, but cannot be used as a replacement for moving joints and hands.
  • Body-powered prostheses are the most common and can be controlled by the person's body movements. Instead of detecting and using specific muscles, body-powered prostheses are controlled by the person actively moving a part of their body, such as the shoulder blade and upper arm movement. The user can also control the prosthesis with their other, non-prosthetic, arm for easier control over the prosthesis.
  • Externally powered myoelectric prostheses are limbs powered by muscles. Sensors placed on the body monitor muscle movement and use algorithms to determine which part of the prothesis should be moved.
  • Hybrid prostheses are a combination of body-powered prostheses and myoelectric prostheses.
  • Activity-specific prostheses have specialized tools for activities that would be hard to perform with basic prostheses alone. Some examples are prostheses that allow the user to grab a hammer, hold a baseball glove, or even swim.

Lower Limb Prostheses

Most lower-limb prostheses need to have a large range of motion. There are 350 different foot/ankle systems and 200 different mechanical knees, so there is a wide selection of lower limb prostheses to choose from.

The three types of lower limb prostheses are:

  • Prosthetic ankle and foot systems, which can utilize AI to determine the best settings and can even provide active propulsion, which makes walking easier and more energy-efficient.
  • Prosthetic knee systems are body-powered and can have multiple joints to provide different rotation points. These systems can be controlled by a microprocessor, or a computer chip, for more stability while moving.
  • Sport-specific prosthetic foot and knee systems are specially designed for different sports, such as running, swimming, or skiing. Unfortunately, amputees who require an artificial knee will have much more difficulty running as a microprocessor cannot compare to a natural muscle-controlled knee.