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Biotechnology. Prosthetics. “Imagine an artificial arm that moves naturally in response to your thoughts, that allows you to feel both the outside world and your own movements, and that is as strong and graceful as an intact, biological limb.”. What are prostheses?.

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  • Prosthetics

“Imagine an artificial arm that moves naturally in response to your thoughts, that allows you to feel both the outside world and your own movements, and that is as strong and graceful as an intact, biological limb.”

What are prostheses

What are prostheses?

  • An artificial extension that replaces a missing body part.

  • Usually replace parts lost by injury or missing from birth or to supplement defective body parts.

  • An artificial limb is a type of prosthesis

A United States Army soldier plays table football with two prosthetic arms

Jon Comer, professional skateboarder with a prosthetic leg.

The numbers

The Numbers

  • Trauma is the second leading cause of amputation in the U.S.

  • About 30,000 traumatic amputations occur in this country every year.

    • Four of every five traumatic amputation victims are male, and most of them are between the ages of 15–30.

  • Traumatic amputation most often affects limbs and appendages like the arms, ears, feet, fingers, hands, legs, and nose.

  • More than 90% of amputations performed in the United States are due to circulatory complications of diabetes, the most common cause of non-traumatic leg and foot amputations.

The numbers1

The Numbers

  • In the United States, the most common causes of lower-extremity amputation are:

  • Disease (70%)

  • Trauma (22%)

  • Congenital or Birth Defects (4%)

  • Tumors (4%)

  • Diseases that can cause amputation are varied, but the most common ones are vascular disease and diabetes. Vascular disease limits the circulation to the extremities. Diabetes, which affects blood sugar, can decrease the body's ability to heal itself.

  • Trauma resulting in amputation is most frequently related to motor vehicle accidents and industrial accidents.

  • Congenital malformation or birth defects can result in either the person having no limb or a very short limb that is treated as an amputation, for which a prosthetic device is made.

  • Tumors of the bone, called osteosarcoma, can sometimes be treated by amputation of the limb.



  • EGYPTIAN TIMES: mummies found with prosthetic limbs made of fiber

  • THE DARK AGES: basic peg legs and hand hooks

    • Prostheses were more cosmetic than functional; meant to hide disgrace and weakness of defeat from other battles.

  • RENAISSANCE: Ambroise Pare (contributed to amp. Surgery and prosthetics)

    • invented "Le Petit Lorrain" (a hand operated by springs and catches)

  • Armorers in the 15th and 16th centuries made artificial limbs out of iron for soldiers who lost limbs. Over the next several centuries, craftsmen began to develop artificial limbs from wood instead of metal because of the lighter weight of the material.



History continued

History continued…

  • 1600's - 1800's: refinements of the prosthetic and surgical principles; invention of the tourniquet, anesthesia, analeptics, blood clotting styptics, and disease fighting drugs

  • Late 19th century: artificial limbs became more widespread due to the large number of amputees from the Civil War.

    • Technology improved primarily for two reasons: the availability of government funding and the discovery of anesthetics.

  • After World War II, the Artificial Limb Program was started in 1945 by the National Academy of Sciences. This program helped improve artificial limbs by promoting and coordinating scientific research on prosthetic devices.

  • In 1962 the government guaranteed prostheses for veterans who lost them in the war.



  • 20th Century: Modern plastics are stronger and more lightweight. The most exciting development has been the development of myoelectric prosthetic limbs (uses electrical signals from arm muscles to move limb).

  • RECENTLY: Computers have been used to help fit amputees with prosthetic limbs. Eighty-five percent of private prosthetic facilities use a CAD/CAM to design a model of the patient's arm or leg, which can be used to prepare a mold from which the new limb can be shaped.

  • A great deal of emphasis has been placed on developing artificial limbs that look and move more like actual human limbs.

  • Advances in biomechanical understanding, the development of new plastics, and the use of computer aided design and computer aided manufacturing have all contributed in the development of more realistic artificial limbs



What are they made of

What are they made of?

  • The typical prosthetic device consists of a custom fitted socket, an internal structure (also called a pylon), knee cuffs and belts that attach it to the body, prosthetic socks that cushion the area of contact, and, in some cases, realistic-looking skin.

  • Should be lightweight; hence, much of it is made from plastic.

  • The socket is usually made from polypropylene.

  • Lightweight metals such as titanium and aluminum have replaced much of the steel in the pylon.

  • Newest development in prosthesis manufacture has been the use of carbon fiber to form a lightweight pylon.

  • The feet are made from urethane foam with a wooden inner keel construction. Other materials commonly used are plastics such as polyethylene, polypropylene, acrylics, and polyurethane.

  • Prosthetic socks are made from a number of soft yet strong fabrics.

  • Physical appearance of the prosthetic limb is important to the amputee. The majority of endoskeletal prostheses (pylons) are covered with a soft polyurethane foam cover that has been designed to match the shape of the patient's sound limb. This foam cover is then covered with a sock or artificial skin that is painted to match the patient's skin color.

How are they made

How are they made?

Must be prescribed first, and then fitted.

Measuring and casting

  • 1 Accuracy and attention to detail; comfortable and useful; Prosthetist evaluates the amputee.

  • 2 Prosthetist measures the lengths of body segments and determines location of bones and tendons in the remaining part of the limb. A plaster cast of the stump is made.

    Making the socket

  • 3 A sheet of clear thermoplastic is heated and then vacuum-formed around the positive mold. This thermoplastic sheet is now the test socket; it is transparent so that the prosthetist can check the fit.

  • 4 Ensure that the test socket fits properly. (if it is a leg, then the prosthetist studies the gait); explain how the fit feels; comfort comes first.

  • 5 The permanent socket is then formed; usually made of polypropylene and is vacuum-formed over a mold in the same way as the test socket.

    Fabrication of the prosthesis

  • 6 Plastic pieces are made in the usual plastic forming methods: vacuum-forming, injecting molding—forcing molten plastic into a mold and letting it cool—and extruding, in which the plastic is pulled through a shaped die. Pylons that are made of titanium or aluminum can be die-cast; in this process, liquid metal is forced into a steel die of the proper shape. The wooden pieces can be planed, sawed, and drilled. The various components are put together using bolts, adhesives, and laminating.

  • 7 The entire limb is assembled by the prosthetist's technician; uses a torque wrench and screwdriver to bolt the prosthetic device together. Prosthetist fits the permanent socket to the patient, this time with the completed custom-made limb attached. Final adjustments are then made.

Types of artificial limbs

Types of Artificial Limbs

  • The type of prosthesis depends on what part of the limb is missing.

  • Transtibial Prosthesis : an artificial limb that replaces a leg missing below the knee.

    • Usually able to regain normal movement because of knee (allows for easier movement)

  • Transfemoral Prostheses: an artificial limb that replaces a leg missing above the knee.

    • very difficult regaining normal movement; must use 80% more energy to walk than a person with two whole legs (due to the complexities in movement associated with the knee)

  • Transradial Prostheses: an artificial limb that replaces an arm missing below the elbow.

    • Cable operated limbs (attaching a harness and cable around the opposite shoulder of the damaged arm)

    • Myoelectric arms

  • Transhumeral Prostheses: an artificial limb that replaces an arm missing above the elbow.

    • same problems as transfemoral amputees because of complexities of the elbow. Makes mimicking the correct motion with an artificial limb very difficult.

How do they work artificial arms

How do they work?-Artificial Arms

  • If you are an arm amputee, your choices range from a passive to a more functional prosthesis.

    • Passive arms have no grasping function but have a good cosmetic appearance.

    • Functional arms can either be body-powered or electric (most often myoelectric). Cable-operated hands and hooks are known as "body-powered" prostheses and are operated by means of a cable and harness system. By using the back and shoulder muscles, the cable is pulled which either opens ("voluntary opening") or closes ("voluntary closing") the hand.

    • A "myoelectric" prosthesis is operated when the electrodes pick up muscle impulses from your residual limb. They are translated into electrical signals that are sent to the electric hand to open or close it. Power is provided by a battery.


Myoelectric Arm

Gait cycle

Gait Cycle

-the series of movements of the leg and foot between one touch of the heel on the ground and the next time the same heel touches.


  • The C-Leg allows the wearer to:

  • seamlessly speed up or slow down

  • take on hills or slopes

  • recover from stumbles 

  • go down stairs step-over-step

  • The science behind the knee is revolutionary. It anticipates what the wearer is doing and accommodates every change, in real time... by utilizing microprocessors to control the knee's hydraulic function 50 times a second.

How do they work feet

How do they work?-Feet

Depend on preference, activity level, some are more flexible than others

The Trias+ foot was modeled after the anatomical function of the human foot. It was engineered to ensure effortless, unified function. The design combines dual spring elements in the heel and forefoot. Made of carbon fiber that can support for patients who weigh up to 275 pounds.




  • Transradial and transtibial prostheses typically cost between US $6,000 and $8,000.

  • Transfemoral and transhumeral prosthetics cost approximately twice much with a range of $10,000 to $15,000 and can sometimes reach costs of $35,000.

  • The cost of an artificial limb does recur because artificial limbs are usually replaced every 3-4 years due to wear and tear on the artificial limb. In addition, if the artificial limb has fit issues, the limb must be replaced within several months



  • Continue to develop limbs whose function is more and more similar to the real thing

  • Direct bone attachment (osseointegration)

    • attaching prosthetic legs to a titanium bolt placed directly in the bone

      (+) may avoid skin sores, sweating, and pain

      (+) Amputees have better muscle control of the prosthetic.

      (+) Amputees can wear the prosthetic for an extended period of time - with the stump and socket method this is not possible.

      (+)Transfemoral amputees are more able to drive a car.

      (-) cannot have large impacts on the limb, such as those experienced during jogging

  • Biohybrid limbs

    • Insert microchips into muscles to pick up signals from the brain

    • Two-way talk (send and receive)

    • Sensitive to touch and heat

Jesse Sullivan demonstrates one of his prosthetic arms by using a paint roller on the side of his house in Dayton, Tenn., July 20, 2006. His left arm is a bionic device wired directly into his brain. Sullivan lost his arms in May 2001, while working as a utility lineman.



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