Body-powered arms Prosthesis

1 body-powered arms

1.1 sockets
1.2 wrists
1.3 voluntary opening , voluntary closing
1.4 feedback
1.5 terminal devices

1.5.1 hooks
1.5.2 hands


1.6 commercial providers , materials

body-powered arms

current technology allows body powered arms weigh around one-half one-third of myoelectric arm does.

sockets

current body-powered arms contain sockets built hard epoxy or carbon fiber. these sockets or interfaces can made more comfortable lining them softer, compressible foam material provides padding bone prominences. self suspending or supra-condylar socket design useful short mid range below elbow absence. longer limbs may require use of locking roll-on type inner liner or more complex harnessing augment suspension.

wrists

wrist units either screw-on connectors featuring unf 1/2-20 thread (usa) or quick-release connector, of there different models.

voluntary opening , voluntary closing

two types of body powered systems exist, voluntary opening pull open , voluntary closing pull close . virtually split hook prostheses operate voluntary opening type system.

more modern prehensors called grips utilize voluntary closing systems. differences significant. users of voluntary opening systems rely on elastic bands or springs gripping force, while users of voluntary closing systems rely on own body power , energy create gripping force.

voluntary closing users can generate prehension forces equivalent normal hand, upwards or exceeding 1 hundred pounds. voluntary closing grips require constant tension grip, human hand, , in property come closer matching human hand performance. voluntary opening split hook users limited forces rubber or springs can generate below 20 pounds.

feedback

an additional difference exists in biofeedback created allows user feel being held. voluntary opening systems once engaged provide holding force operate passive vice @ end of arm. no gripping feedback provided once hook has closed around object being held. voluntary closing systems provide directly proportional control , biofeedback user can feel how force applying.

a recent study showed stimulating median , ulnar nerves, according information provided artificial sensors hand prosthesis, physiologically appropriate (near-natural) sensory information provided amputee. feedback enabled participant modulate grasping force of prosthesis no visual or auditory feedback.

researchers École polytechnique fédérale de lausanne in switzerland , scuola superiore sant anna in italy, implanted electrodes amputee s arm in february 2013. study, published wednesday in science translational medicine, details first time sensory feedback has been restored allowing amputee control artificial limb in real-time. wires linked nerves in upper arm, danish patient able handle objects , instantly receive sense of touch through special artificial hand created silvestro micera , researchers both in switzerland , italy.

terminal devices

terminal devices contain range of hooks, prehensors, hands or other devices.

hooks

voluntary opening split hook systems simple, convenient, light, robust, versatile , relatively affordable.

a hook not match normal human hand appearance or overall versatility, material tolerances can exceed , surpass normal human hand mechanical stress (one can use hook slice open boxes or hammer whereas same not possible normal hand), thermal stability (one can use hook grip items boiling water, turn meat on grill, hold match until has burned down completely) , chemical hazards (as metal hook withstands acids or lye, , not react solvents prosthetic glove or human skin).

hands

actor owen wilson gripping myoelectric prosthetic arm of united states marine

prosthetic hands available in both voluntary opening , voluntary closing versions , because of more complex mechanics , cosmetic glove covering require relatively large activation force, which, depending on type of harness used, may uncomfortable. recent study delft university of technology, netherlands, showed development of mechanical prosthetic hands has been neglected during past decades. study showed pinch force level of current mechanical hands low practical use. best tested hand prosthetic hand developed around 1945. in 2017 however, research has been started bionic hands laura hruby of medical university of vienna. companies producing robotic hands integrated forearm, fitting unto patient s upper arm.

commercial providers , materials

hosmer , otto bock major commercial hook providers. mechanical hands sold hosmer , otto bock well; becker hand still manufactured becker family. prosthetic hands may fitted standard stock or custom-made cosmetic looking silicone gloves. regular work gloves may worn well. other terminal devices include v2p prehensor, versatile robust gripper allows customers modify aspects of it, texas assist devices (with whole assortment of tools) , trs offers range of terminal devices sports. cable harnesses can built using aircraft steel cables, ball hinges , self lubricating cable sheaths. prosthetics have been designed use in salt water.