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Bionics 4. Kevin Warwick. Artificial Limbs. An artificial limb usually replaces a missing limb, such as an arm or leg. The type of artificial limb used is determined largely by the extent of amputation of the missing extremity – each one is a little different.
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Bionics 4 Kevin Warwick
Artificial Limbs • An artificial limb usually replaces a missing limb, such as an arm or leg. • The type of artificial limb used is determined largely by the extent of amputation of the missing extremity – each one is a little different. • Reasons include disease, accidents, and congenital (birth) defects.
Geography • Likely reasons for an amputation depend on location. • In USA & Europe circulatory disease, cancer and infection are the leading causes. • In Africa the most likely causes are industrial, vehicular, or a war related accidents – again infection is a problem.
This Presentation • More interested in the legs and arms themselves • Neuroprosthetics & Enhancements etc are mostly a separate lecture
History • Two artificial toes have been found on Egyptian mummies – these date back to 1,000BC. However it is not known if they were actually used in life. • The first artificial leg, from archaeology, is the Roman Capua Leg. This was found in a tomb in Capua, Italy, and dates back to 300BC. It was made of wood and copper. • In the 15th century artificial limbs were often made out of iron for soldiers and sailors. However wood came to be used much more, simply because of its weight.
Wooden Legs • Such a wooden leg could be simply fixed. • Or it could be hinged at the knee to assist walking • No hinge – possible strange gait
Developments • In the 19th century, artificial limbs became more widespread due to the large number of amputees from wars. • Helped by the discovery of anesthetics. • In the 20th century scientific research and commercial possibilities opened the field further. • In recent years, a great deal of emphasis has been placed on developing artificial limbs that look and move more like actual human limbs. • General new technology (plastics, CAD, manufacturing, medicine) have all improved the end results.
Types of Prosthetic • Transtibial Prosthesis replaces a leg missing below the knee. Such amputees can regain normal movement more readily than those with a transfemoral amputation - retaining the knee allows for easier movement. • Transfemoral Prostheses replaces a leg missing above the knee. Such amputees can have a very difficult time regaining normal movement. A transfemoral amputee must use approximately 80% more energy to walk than a person with two whole legs. • Transradial Prostheses replaces an arm missing below the elbow. Two main types of prosthetics are available. Cable operated limbs work by attaching a harness and cable around the opposite shoulder of the damaged arm. Alternative is myoelectric arms – muscle sensing. • Transhumeral Prosthesis replaces an arm missing above the elbow. Such amputees experience some of the same problems as transfemoral amputees, due to the similar complexities associated with the movement of the elbow. Mimicking the correct motion with an artificial limb is very difficult.
Recent Developments • New plastics and other materials, such as carbon fibre, have allowed artificial limbs to be stronger and lighter, limiting the amount of extra energy necessary to operate the limb. This is especially important for transfemoral amputees. • Other synthetic materials have allowed artificial limbs to look much more realistic, which is important to transradial and transhumeral amputees because they are more likely to have the artificial limb exposed.
Artificial Legs • Is only one leg missing? • How much of the leg is missing? • Clearly these issues are vital to the type of artificial leg needed • The more to be replaced, so the more difficult the problem is.
C-Leg • The best known present day artificial leg is the C-Leg produced by Otto Block. • The user can choose between two modes: one for walking and one for bicycling (or any other preprogrammed activity). The "problem" is switching between modes, as the wearer has to swing the leg forward in a jerky fashion. • The C-LEG supports up to 10 programmable modes, switchable through a small remote control device about the size of a car alarm remote. Reprogramming a mode with another special activity requires a technician.
C-Leg • An inbuilt microprocessor interprets the user’s movements and anticipates their actions, allowing motion changes in real time. • The system is actuated through the leg’s hydraulic movement. • It gives users greater flexibility to change speed or direction without sacrificing stability.
C-Leg • The 10 switchable modes enable various sports activities, including cycling, running, natural driving and other programmable activities that require different leg actions to normal walking and stair climbing. • Current challenges are to stretch the unit’s battery life to 50 hours on one charge and to make the leg salt-water resistant. These are both requirements to support military use.
Heather Mills • In August 1993 Heather was hit by a police motorcycle by Kensington Palace, London. • Her injuries included crushed ribs and a punctured lung. She needed a metal plate put into her pelvis and also the amputation of her left leg below the knee. • Mills has a prosthetic leg, taking it off and showing it to USA talk show host Larry King during his interview with her in October 2002.
Feet • With artificial legs usually the knee joint is critical • Feet tend to be either non-existent, e.g. Aimee Mullins, or are more for cosmetic purposes – they are not functional • Stability is important but not dexterity • Tend to be purpose directed – what is the leg for?
Artificial arms and hands • Stability and power carrying are not big issues here • Elbow joints clearly are important • But most critical are hand movements – what will the hand have to do? – how is it to be controlled? – what will it look like? • Functionality is important – but cosmetics are also very important
Artificial Arms and Hands • Important if one or both have been lost • It is possible to do many activities with one hand or using a residual limb(s). • Many arm amputees do not use any prostheses or special tools. It is easy and possible to get dressed/write/type with one hand. • Some continue their work with a special attachment only e.g. carpentry, car driving. • Nevertheless, having a prosthesis can be a big help, especially for manual labour.
Prosthesis • Learning to use a prosthesis takes hard work and practice. It is only worth the effort if it improves a person’s ability to hold and use things. • An arm-hand prosthesis has three basic parts: the socket, which fits over the residual limb; the arm section, which may or may not include an elbow joint; and the hand/tool, which can be like a hand, a hook, or some other shape to allow the person to hold and use things. • Often a hook is preferred as it is extremely functional
Body-powered prostheses • Some prosthetics clinics make available body-powered arm prostheses. • These have straps or cables that attach to other parts of the body, so that by moving a shoulder, the person can make the hand close or bend the elbow of the prosthesis. • Body-powered prostheses often have metal hooks instead of fingers. The hooks are better than artificial fingers for hard work and can pick up smaller things.
Electric-powered prostheses • Electrical prostheses are available in some countries, but they are relatively expensive. • Perhaps not available where they are needed - most (countries at war/strife). • Muscles in the arm operate electric motors, which close and open the hand. • Electrical prostheses look more like real arms, but they are not as strong and they break more easily.
Cosmetic prostheses • Cosmetic arms look like real arms but the hands either do not move at all or can be pulled (by another hand) into a fixed position. • They can help a little (for example, the cosmetic arm can hold down a paper while the other hand writes on it), but the real purpose of a cosmetic arm is to look natural. • Very useful for someone in the public eye. • Useful if only one hand has been lost.
Krukenberg surgery • Some people missing both hands choose to have surgery, called the Krukenberg surgery. • This separates the two bones of the forearm to make a new kind of “hand.” • The bones can be used like two fingers, and because the skin and bones are real, the person can feel what they are doing. • This greatly benefits amputees who are blind. • It is still possible to wear a prosthesis over the residual limb even after the surgery.
The i-LIMB Hand • From Touch Bionics • http://www.touchbionics.com/
The i-LIMB Hand • The i-LIMB Hand is controlled by a system that uses a two-input myoelectric (muscle signal) to open and close the hand’s fingers.. This signal is picked up by electrodes that sit on the surface of the skin. Existing users of basic myoelectric prosthetic hands are able to adapt to the system and can master the device’s functionality within minutes.
Bionic Arm • In 2001 Jesse Sullivan lost both his arms when he was electrocuted. • He has received an artificial arm/hand controlled from his nervous system. • The nerves that used to go to the arm were moved onto chest muscles. The nerves grew into the chest muscles, so when Jesse thinks "close hand," a portion of his chest muscle contracts and electrodes that detect this muscle activity tell the computerized arm to close the hand. Thus, Jesse thinks "close hand" and his artificial hand closes. • Work of Todd Kuiken.
Claudia Mitchell • Lost her left arm in a motorcycle accident. • In 2007 became the 4th person to have this type of procedure – Rehab Institute of Chicago
Next Lecture • Deep Brain Stimulation
