The function of the human hand has been the most difficult engineering problem to solve in prosthetics. The simultaneous multiple movements and ability to conform to and grip objects with varying degrees of pressure while providing feedback to the brain without visual confirmation is simply incredible. Upper limb prosthetics has lagged behind the technology curve for several decades. Body powered terminal devices are still commonly provided. They do have a place for heavy work such as lifting and holding tools with the most commonly known hook. Mechanical hands do provide a level of simple function; pinching of the second and third finger tips and thumb, and restored appearance.
Northeast Orthotics and Prosthetics provides upper limb socket technology using flexible interfaces that are self suspended by design and by suction via silicone liners and soft tissue tension. We treat all levels of upper limb amputations.
Wrist Disarticulation and Trans Radial Prostheses (Below Elbow)
Wrist disarticulations can be beneficial because the shape of the forearm just above the hand resembles a screw driver which allows for rotation of the terminal device to remain actively controlled by body motion. The shorter the length of trans radial amputation is, the more the elbow has to be encompassed and range of motion minimized. However, the shorter the length the more electronic function can be integrated into the space of the forearm; such as, wrists that rotate and flex.
Trans Humeral Prosthesis (Above Elbow)
This level of amputation offers more of a learning challenge for the amputee in that both the elbow and terminal device needs to be controlled. Myoelectric components allow for these functions to be actuated simultaneously in some instances. Multiple electrode sites in the socket and expertise by the amputee in isolating muscle contractions are necessary for success. Most trans humeral sockets are suspended by skin tension suction.
Shoulder Disarticulation and Forequarter Prostheses
This level of amputation is so complex in providing a worthwhile prosthesis that the best success is found at research centers such as the Rehabilitation Institute of Chicago.
The i-LIMB Hand produced by Touch Bionics is the first commercially available prosthetic hand that features five individually powered fingers. The artificial hand looks and acts like a real human hand. It works by using a traditional myoelectric two-signal input sourced from sensors placed on the skin to collect muscle-generated signals. The individual articulating fingers, rotating thumb and a range of grip patterns help the amputee tackle everyday activities easily. The revolutionary functionality coupled with the amazing natural cosmetic of the hand will change the lives of above and below elbow amputees.
The i-LIMB Hand has been named a winner in the 2009 Wall Street Journal Technology Innovation Awards, an award that focus on the overall innovation of products, services, or inventions which are technological breakthroughs in such areas as medicine, software, the Internet, wireless and consumer electronics. The hand also won top honors in the Medical-Devices category.
External powered prostheses that were introduced in the 1970's by myoelectric and switch controlled terminal devices still relied on grip force to accomplish daily tasks. They did, however, eliminate the harness and allowed the amputee to operate his prosthesis in a greater range of motion and position than before.
Fortunately, research has advanced with the government agency DARPA's involvement and funding to provide our returning soldiers from the Middle East with better upper limb prosthetics. Also, the introduction of the i-Limb by Touch Bionics is another improvement in function. This is an externally powered hand that has five separate motors, one for each digit, and is capable of gradually contracting all of the joints of the fingers until an object is uniformly grasped. The thumb is able to be passively positioned in opposition or abduction which allows for another spectrum of grip patterns. This technology is indeed a step forward. Otto Bock is also a leading innovator in electronic hands. They have introduced a hand that is suitable for some partial hand amputations.