jacob george. the group of researchers implanted electrodes into the patient's arm to map out several sensory precepts. they would then stimulate each electrode to figure out how each sensory precept was triggered, then proceed to map the sensory information onto the prosthetic. this would allow the researchers to get a good approximation of the same kind of information that the patient would receive from their natural hand. unfortunately, the arm is too expensive for the average user to acquire, however, jacob mentioned that insurance companies could cover the costs of the prosthetic. terminal devices terminal devices contain a range of hooks, prehensors, hands or other devices. hooks voluntary opening split hook systems are simple, convenient, light, robust, versatile and relatively affordable. a hook does not match a normal human hand for appearance or overall versatility, but its material tolerances can exceed and surpass the normal human hand for mechanical stress (one can even use a hook to slice open boxes or as a hammer whereas the same is not possible with a normal hand), for thermal stability (one can use a hook to grip items from boiling water, to turn meat on a grill, to hold a match until it has burned down completely) and for chemical hazards (as a metal hook withstands acids or lye, and does not react to solvents like a prosthetic glove or human skin). hands actor owen wilson gripping the myoelectric prosthetic arm of a united states marine prosthetic hands are available in both voluntary opening and voluntary closing versions and because of their more complex mechanics and cosmetic glove covering require a relatively large activation force, which, depending on the type of harness used, may be uncomfortable. a recent study by the delft university of technology, the netherlands, showed that the development of mechanical prosthetic hands has been neglected during the past decades. the study showed that the pinch force level of most current mechanical hands is too low for practical use. the best tested hand was a prosthetic hand developed around 1945. in 2017 however, a research has been started with bionic hands by laura hruby of the medical university of vienna. a few open-hardware 3-d printable bionic hands have also become available. some companies are also producing robotic hands with integrated forearm, for fitting unto a patient's upper arm and in 2020, at the italian institute of technology (iit), another robotic hand with integrated forearm (soft hand pro) was developed. commercial providers and materials hosmer and otto bock are major commercial hook providers. mechanical hands are sold by hosmer and otto bock as well; the becker hand is still manufactured by the becker family. prosthetic hands may be fitted with standard stock or custom-made cosmetic looking silicone gloves. but regular work gloves may be worn as well. other terminal devices include the v2p prehensor, a versatile robust gripper that allows customers to modify aspects of it, texas assist devices (with a whole assortment of tools) and trs that offers a range of terminal devices for sports. cable harnesses can be built using aircraft steel cables, ball hinges, and self-lubricating cable sheaths. some prosthetics have been designed specifically for use in salt water. lower-extremity prosthetics a prosthetic leg worn by ellie cole lower-extremity prosthetics describes artificially replaced limbs located at the hip level or lower. concerning all ages ephraim et al. (2003) found a worldwide estimate of all-cause lower-extremity amputations of 2.0–5.9 per 10,000 inhabitants. for birth prevalence rates of congenital limb deficiency they found an estimate between 3.5 and 7.1 cases per 10,000 births. the two main subcategories of lower extremity prosthetic devices are trans-tibial (any amputation transecting the tibia bone or a congenital anomaly resulting in a tibial deficiency), and trans-femoral (any amputation transecting the femur bone or a congenital anomaly resulting in a femoral 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: 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. knee disarticulations – this usually refers to an amputation through the knee disarticulating the femur from the tibia. symes – this is an ankle disarticulation while preserving the heel pad. socket the socket serves as an interface between the residuum and the prosthesis, ideally allowing comfortable weight-bearing, movement control and proprioception. socket problems, such as discomfort and skin breakdown, are rated among the most important issues faced by lower-limb amputees. shank and connectors this part creates distance and support between the knee-joint and the foot (in case of an upper-leg prosthesis) or between the socket and the foot. the type of connectors that are used between the shank and the knee/foot determines whether the prosthesis is modular or not. modular means that the angle and the displacement of the foot in respect to the socket can be changed after fitting. in developing countries prosthesis mostly are non-modular, in order to reduce cost. when considering children modularity of angle and height is important because of their average growth of 1.9 cm annually. foot providing contact to the ground, the foot provides shock absorption and stability during stance. additionally it influences gait biomechanics by its shape and stiffness. this is because the trajectory of the center of pressure (cop) and the angle of the ground reaction forces is determined by the shape and stiffness of the foot and needs to match the subject's build in order to produce a normal gait pattern. andrysek (2010) found 16 different types of feet, with greatly varying results concerning durability and biomechanics. the main problem found in current feet is durability, endurance ranging from 16 to 32 months these results are for adults and will probably be worse for children due to higher activity levels and scale effects. evidence comparing different types of feet and ankle prosthetic devices is not strong enough to determine if one mechanism of ankle/foot is superior to another. when deciding on a device, the cost of the device, a person's functional need, and the availability of a particular device should be considered. knee joint in case of a trans-femoral (above knee) amputation, there also is a need for a complex connector providing articulation, allowing flexion during swing-phase but not during stance. as its purpose is to replace the knee, the prosthetic knee joint is the most critical component of the prosthesis for trans-femoral amputees. the function of the good prosthetic knee joint is to mimic the function of the normal knee, such as providing structural support and stability during stance phase but able to flex in a controllable manner during swing phase. hence it allows users to have a smooth and energy efficient gait and minimize the impact of amputation. the prosthetic knee is connected to the prosthetic foot by the shank, which is usually made of an aluminum or graphite tube. one of the most important aspect of a prosthetic knee joint would be its stance-phase control mechanism. the function of stance-phase control is to prevent the leg from buckling when the limb is loaded during weight acceptance. this ensures the stability of the knee in order to support the single limb support task of stance phase and provides a smooth transition to the swing phase. stance phase control can be achieved in several ways including the mechanical locks, relative alignment of prosthetic components, weight activated friction control, and polycentric mechanisms. microprocessor control to mimic the knee's functionality during gait, microprocessor-controlled knee joints have been developed that control the flexion of the knee. some examples are otto bock's c-leg, introduced in 1997, ossur's rheo knee, released in 2005, the power knee by ossur, introduced in 2006, the plié knee from freedom innovations and daw industries' self learning knee (slk). the idea was originally developed by kelly james, a canadian engineer, at the university of alberta. a microprocessor is used to interpret and analyze signals from knee-angle sensors and moment sensors. the microprocessor receives signals from its sensors to determine the type of motion being employed by the amputee. most microprocessor controlled knee-joints are powered by a battery housed inside the prosthesis. the sensory signals computed by the microprocessor are used to control the resistance generated by hydraulic cylinders in the knee-joint. small valves control the amount of hydraulic fluid that can pass into and out of the cylinder, thus regulating the extension and compression of a piston connected to the upper section of the knee. the main advantage of a microprocessor-controlled prosthesis is a closer approximation to an amputee's natural gait. some allow amputees to walk near walking speed or run. variations in speed are also possible and are taken into account by sensors and communicated to the microprocessor, which adjusts to these changes accordingly. it also enables the amputees to walk downstairs with a step-over-step approach, rather than the one step at a time approach used with mechanical knees. there is some research suggesting that people with microprocessor-controlled prostheses report greater satisfaction and improvement in functionality, residual limb health, and safety. people may be able to perform everyday activities at greater speeds, even while multitasking, and reduce their risk of falls. however, some have some significant drawbacks that impair its use. they can be susceptible to water damage and thus great care must be taken to ensure that the prosthesis remains dry. myoelectric a myoelectric prosthesis uses the electrical tension generated every time a muscle contracts, as information. this tension can be captured from voluntarily contracted muscles by electrodes applied on the skin to control the movements of the prosthesis, such as elbow flexion/extension, wrist supination/pronation (rotation) or opening/closing of the fingers. a prosthesis of this type utilizes the residual neuromuscular system of the human body to control the functions of an electric powered prosthetic hand, wrist, elbow or foot. this is different from an electric switch prosthesis, which requires straps and/or cables actuated by body movements to actuate or operate switches that control the movements of the prosthesis. there is no clear evidence concluding that myoelectric upper extremity prostheses function better than body-powered prostheses. advantages to using a myoelectric upper extremity prosthesis include the potential for improvement in cosmetic appeal (this type of prosthesis may have a more natural look), may be better for light everyday activities, and may be beneficial for people experiencing phantom limb pain. when compared to a body-powered prosthesis, a myoelectric prosthesis may not be as durable, may have a longer training time, may require more adjustments, may need more maintenance, and does not provide feedback to the user. prof. alvaro ríos poveda has been working for several years on a non-invasive and affordable solution to this feedback problem. he considers that: "prosthetic limbs that can be controlled with thought hold great promise for the amputee, but without sensorial feedback from the signals returning to the brain, it can be difficult to achieve the level of control necessary to perform precise movements. when connecting the sense of touch from a mechanical hand directly to the brain, prosthetics can restore the function of the amputated limb in an almost natural-feeling way." he presented the first myoelectric prosthetic hand with sensory feedback at the xviii world congress on medical physics and biomedical engineering, 1997, held in nice, france. the ussr was the first to develop a myoelectric arm in 1958, while the first myoelectric arm became commercial in 1964 by the central prosthetic research institute of the ussr, and distributed by the hangar limb factory of the uk. robotic prostheses robots can be used to generate objective measures of patient's impairment and therapy outcome, assist in diagnosis, customize therapies based on patient's motor abilities, and assure compliance with treatment regimens and maintain patient's records. it is shown in many studies that there is a significant improvement in upper limb motor function after stroke using robotics for upper limb rehabilitation. in order for a robotic prosthetic limb to work, it must have several components to integrate it into the body's function: biosensors detect signals from the user's nervous or muscular systems. it then relays