Prosthesis

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

In medicine, a prosthesis (plural prostheses; from the Greek πρόσθεσις "addition") is an artificial extension that replaces a missing body part. It is part of the field of biomechatronics, the science of using mechanical devices with human muscle, skeleton, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect. Prostheses are typically used to replace parts lost by injury (traumatic) or missing from birth (congenital) or to supplement defective body parts. Inside the body, artificial heart valves are in common use with artificial hearts and lungs seeing less common use but under active technology development. Other medical devices and aids that can be considered prosthetics include artificial eyes, palatal obturator, gastric bands, and dentures.

History

Roman bronze crowns have also been found, but their use could have been more aesthetic than medical^[1].

A famous and quite refined^[2] historical prosthetic arm was that of Götz von Berlichingen, made in the beginning of the 16th century. Around the same time, François de la Noue is also reported to have had an iron hand, as is, in the 17th century, René-Robert Cavalier de la Salle^[3].

Lower extremity prosthetics

Lower extremity prosthetics describes artificially replaced limbs located at the hip level or lower. The two main subcategories of lower extremity prosthetic devices are 1.trans-tibial (any amputation transecting the tibia bone or a congenital anomaly resulting in a tibial deficiency) and 2.trans-femoral (any amputation transecting the femur bone or a congenital anomaly resulting in a femural deficiency). In the prosthetic industry a trans-tibial prosthetic leg is often referred to as a "BK" or below the knee prosthesis while the trans-femoral prosthetic leg is often referred to as an "AK" or above the knee prosthesis.

Other, less prevalent lower extremity cases include the following:

1. Hip disarticulations - This usually refers to when an amputee or congenitally challenged patient has either an amputation or anomaly at or in close proximity to the hip joint.
2. Knee disarticulations - This usually refers to an amputation through the knee disarticulating the femur from the tibia.
3. Symes - This is an ankle disarticulation while preserving the heel pad.

Lower extremity modern history

Socket technology for lower extremity limbs saw a revolution of advancement during the 1980s when Sabolich Prosthetics, John Sabolich C.P.O., invented the Contoured Adducted Trochanteric-Controlled Alignment Method (CATCAM) socket, later to evolve into the Sabolich Socket. The advancement was due to the difference in the socket to patient contact model. Prior, sockets were made in the shape of a square bucket with no specialized containment for either the patient's bony prominences' or muscular tissue. Sabolich's design held the patient's limb like a glove, locking it into place and distributing the weight evenly over the existing limb as well as the bone structure of the patient. This was the first instance of ischial containment and led to an extreme advancement in patient accomplishment. Because of Sabolich's dedication to research and development in lower extremity prosthetics, Sabolich Prosthetics saw the first above the knee prosthetic patients walk and run step over step with both one leg and two legs missing, walking down stairs, suction sockets, modern plastic and bio elastic sockets, sense of feel technology, and numerous other inventions in the prosthetic field.

Robotic prostheses

In order for a robotic prosthetic limb to work, it must have several components to integrate it into the body's function: [[Biosensor]]s detect signals from the user's nervous or muscular systems. It then relays this information to a controller located inside the device, and processes feedback from the limb and actuator (e.g., position, force) and sends it to the controller. Examples include wires that detect electrical activity on the skin, needle electrodes implanted in muscle, or solid-state electrode arrays with nerves growing through them. One type of these biosensors are employed in myoelectric prosthesis.

Mechanical sensors process aspects affecting the device (e.g., limb position, applied force, load) and relay this information to the biosensor or controller. Examples include force meters and accelerometers.

The controller is connected to the user's nerve and muscular systems and the device itself. It sends intention commands from the user to the actuators of the device, and interprets feedback from the mechanical and biosensors to the user. The controller is also responsible for the monitoring and control of the movements of the device.

An actuator mimics the actions of a muscle in producing force and movement. Examples include a motor that aids or replaces original muscle tissue.

Cosmesis

A French mutilé in 1918 wearing a mask provided by the American Red Cross (left) and without mask (right)

Cosmetic prosthesis has long been used to disguise injuries and disfigurements. With advances in modern technology, cosmesis, the creation of lifelike limbs made from silicone or PVC has been made possible. Such prosthetics, such as artificial hands, can now be made to mimic the appearance of real hands, complete with freckles, veins, hair, fingerprints and even tattoos. Custom-made cosmeses are generally more expensive (costing thousands of US dollars, depending on the level of detail), while standard cosmeses come ready-made in various sizes, although they are often not as realistic as their custom-made counterparts. Another option is the custom-made silicone cover, which can be made to match a person's skin tone but not details such as freckles or wrinkles. Cosmeses are attached to the body in any number of ways, using an adhesive, suction, form-fitting, stretchable skin, or a skin sleeve.

Cognition

Unlike neuromotor prostheses, neurocognitive prostheses would sense or modulate neural function in order to physically reconstitute or augment cognitive processes such as executive function, attention, language, and memory. No neurocognitive prostheses are currently available but the development of implantable neurocognitive brain-computer interfaces has been proposed to help treat conditions such as stroke, traumatic brain injury, cerebral palsy, autism, and Alzheimer's disease.^[4] The recent field of Assistive Technology for Cognition concerns the development of technologies to augment human cognition. Scheduling devices such as Neuropage remind users with memory impairments when to perform certain activities, such as visiting the doctor. Micro-prompting devices such as PEAT, AbleLink and Guide have been used to aid users with memory and executive function problems perform activities of daily living.

Prosthetic enhancement

In addition to the standard artificial limb for everyday use, many amputees or congenital patients have special limbs and devices to aid in the participation of sports and recreational activities.

In 2008, Oscar Pistorius was briefly ruled ineligible for the 2008 Summer Olympics due to an alleged mechanical advantage over runners who have ankles.

Within science fiction, and, more recently, within the scientific community, there has been consideration given to using advanced prostheses to replace healthy body parts with artificial mechanisms and systems to improve function. The morality and desirability of such technologies are being debated. Body parts such as legs, arms, hands, feet, and others can be replaced.

The first experiment with a healthy individual appears to have been that by the British scientist Kevin Warwick. In 2002, an implant was interfaced directly into Warwick's nervous system. The electrode array, which contained around a hundred electrodes, was placed in the median nerve. The signals produced were detailed enough that a robot arm was able to mimic the actions of Warwick's own arm and provide a form of touch feedback again via the implant.^[5]

In early 2008, Oscar Pistorius, the "Blade Runner" of South Africa, was briefly ruled ineligible to compete in the 2008 Summer Olympics because his prosthetic limbs were said to give him an unfair advantage over runners who had ankles. One researcher found that his limbs used twenty-five percent less energy than those of an able-bodied runner moving at the same speed. This ruling was overturned on appeal, with the appellate court stating that the overall set of advantages and disadvantages of Pistorius' limbs had not been considered. Pistorius did not qualify for the South African team for the Olympics, but went on to sweep the 2008 Summer Paralympics, and has been ruled eligible to qualify for any future Olympics.

The "Luke arm" is an advanced prosthesis currently under trials as of 2008.^[6]

See also

• Prosthetist
• Amputation
• Anaplastology
• Artificial organ
• Artificial knee
• Machine
• Cyborg

References

External links

• National Amputee Centre — Information about artificial limbs
• O&PCare has a complete glossary relating to the field of prosthetics
• How Stuff Works : Biomechatronics - An overview of the field of biomechatronics, of which prosthetics is a part