Current technology and manufacturing Prosthesis

1 current technology , manufacturing

1.1 body-powered arms

1.1.1 sockets
1.1.2 wrists
1.1.3 voluntary opening , voluntary closing
1.1.4 feedback
1.1.5 terminal devices

1.1.5.1 hooks
1.1.5.2 hands


1.1.6 commercial providers , materials


1.2 lower-extremity prosthetics

1.2.1 socket
1.2.2 shank , connectors
1.2.3 foot
1.2.4 knee joint

1.2.4.1 microprocessor control




1.3 myoelectric
1.4 robotic prostheses

1.4.1 robotic arms
1.4.2 robotic legs

current technology , manufacturing

knee prosthesis manufactured using worknc computer aided manufacturing software

over years, there have been advancements in artificial limbs. new plastics , other materials, such carbon fiber, have allowed artificial limbs stronger , lighter, limiting amount of energy necessary operate limb. important trans-femoral amputees. additional materials have allowed artificial limbs more realistic, important trans-radial , transhumeral amputees because more have artificial limb exposed.

manufacturing prosthetic finger

in addition new materials, use of electronics has become common in artificial limbs. myoelectric limbs, control limbs converting muscle movements electrical signals, have become more common cable operated limbs. myoelectric signals picked electrodes, signal gets integrated , once exceeds threshold, prosthetic limb control signal triggered why inherently, myoelectric controls lag. conversely, cable control immediate , physical, , through offers degree of direct force feedback myoelectric control not. computers used extensively in manufacturing of limbs. computer aided design , computer aided manufacturing used assist in design , manufacture of artificial limbs.

most modern artificial limbs attached stump of amputee belts , cuffs or suction. stump either directly fits socket on prosthetic, or—more commonly today—a liner used fixed socket either vacuum (suction sockets) or pin lock. liners soft , that, can create far better suction fit hard sockets. silicone liners can obtained in standard sizes, circular (round) cross section, other stump shape, custom liners can made. socket custom made fit residual limb , distribute forces of artificial limb across area of stump (rather 1 small spot), helps reduce wear on stump. custom socket created taking plaster cast of stump or, more commonly today, of liner worn on stump, , making mold plaster cast. newer methods include laser guided measuring can input directly computer allowing more sophisticated design.

one problem stump , socket attachment bad fit reduce area of contact between stump , socket or liner, , increase pockets between stump skin , socket or liner. pressure higher, can painful. air pockets can allow sweat accumulate can soften skin. ultimately, frequent cause itchy skin rashes. on time, can lead breakdown of skin.

artificial limbs typically manufactured using following steps:

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.

lower-extremity prosthetics

a prosthetic leg worn ellie cole

lower-extremity prosthetics describes artificially replaced limbs located @ hip level or lower. concerning ages ephraim et al. (2003) found worldwide estimate of all-cause lower-extremity amputations of 2.0–5.9 per 10,000 inhabitants. birth prevalence rates of congenital limb deficiency found estimate between 3.5–7.1 cases per 10,000 births.

the 2 main subcategories of lower extremity prosthetic devices trans-tibial (any amputation transecting tibia bone or congenital anomaly resulting in tibial deficiency), , trans-femoral (any amputation transecting femur bone or congenital anomaly resulting in femoral deficiency). in prosthetic industry trans-tibial prosthetic leg referred bk or below knee prosthesis while trans-femoral prosthetic leg referred ak or above knee prosthesis.

other, less prevalent lower extremity cases include following:

socket

this important part serves interface between residuum , prosthesis, allowing comfortable weight-bearing, movement control , proprioception. fitting 1 of challenging aspects of entire prosthesis. difficulties accompanied socket needs have perfect fit, total surface bearing prevent painful pressure spots. needs flexible, sturdy, allow normal gait movement not bend under pressure.

shank , connectors

this part creates distance , support between knee-joint , foot (in case of upper-leg prosthesis) or between socket , foot. type of connectors used between shank , knee/foot determines whether prosthesis modular or not. modular means angle , displacement of foot in respect socket can changed after fitting. in developing countries prosthesis non-modular, in order reduce cost. when considering children modularity of angle , height important because of average growth of 1.9 cm annually.

foot

providing contact ground, foot provides shock absorption , stability during stance. additionally influences gait biomechanics shape , stiffness. because trajectory of center of pressure (cop) , angle of ground reaction forces determined shape , stiffness of foot , needs match subject s build in order produce normal gait pattern. andrysek (2010) found 16 different types of feet, varying results concerning durability , biomechanics. main problem found in current feet durability, endurance ranging 16–32 months these results adults , worse children due higher activity levels , scale effects.

knee joint

in case of trans-femoral amputation there need complex connector providing articulation, allowing flexion during swing-phase not during stance.

microprocessor control

to mimic knee s functionality during gait, microprocessor-controlled knee joints have been developed control flexion of knee. examples otto bock’s c-leg, introduced in 1997, ossur s rheo knee, released in 2005, power knee ossur, introduced in 2006, plié knee freedom innovations , daw industries’ self learning knee (slk).

the idea developed kelly james, canadian engineer, @ university of alberta.

a microprocessor used interpret , analyse signals knee-angle sensors , moment sensors. microprocessor receives signals sensors determine type of motion being employed amputee. microprocessor controlled knee-joints powered battery housed inside prosthesis.

the sensory signals computed microprocessor used control resistance generated hydraulic cylinders in knee-joint. small valves control amount of hydraulic fluid can pass , out of cylinder, regulating extension , compression of piston connected upper section of knee.

the main advantage of microprocessor-controlled prosthesis closer approximation amputee’s natural gait. allow amputees walk near walking speed or run. variations in speed possible , taken account sensors , communicated microprocessor, adjusts these changes accordingly. enables amputees walk down stairs step-over-step approach, rather 1 step @ time approach used mechanical knees. however, have significant drawbacks impair use. can susceptible water damage , great care must taken ensure prosthesis remains dry.

myoelectric

a myoelectric prosthesis uses electrical tension generated every time muscle contracts, information. tension can captured voluntarily contracted muscles electrodes applied on skin control movements of prosthesis, such elbow flexion/extension, wrist supination/pronation (rotation) or opening/closing of fingers. prosthesis of type utilizes residual neuromuscular system of human body control functions of electric powered prosthetic hand, wrist, elbow or foot. different electric switch prosthesis, requires straps and/or cables actuated body movements actuate or operate switches control movements of prosthesis.

the ussr first develop myoelectric arm in 1958, while first myoelectric arm became commercial in 1964 central prosthetic research institute of ussr, , distributed hangar limb factory of uk.

researchers @ rehabilitation institute of chicago announced in september 2013 have developed robotic leg translates neural impulses user s thigh muscles movement, first prosthetic leg so. in testing.

robotic prostheses

robots can used generate objective measures of patient s impairment , therapy outcome, assist in diagnosis, customize therapies based on patient s motor abilities, , assure compliance treatment regimens , maintain patient s records. shown in many studies there significant improvement in upper limb motor function after stroke using robotics upper limb rehabilitation. in order robotic prosthetic limb work, must have several components integrate body s function: biosensors detect signals user s nervous or muscular systems. relays information controller located inside device, , processes feedback limb , actuator (e.g., position, force) , sends controller. examples include surface electrodes detect electrical activity on skin, needle electrodes implanted in muscle, or solid-state electrode arrays nerves growing through them. 1 type of these biosensors employed in myoelectric prostheses.

a device known controller connected user s nerve , muscular systems , device itself. sends intention commands user actuators of device, , interprets feedback mechanical , biosensors user. controller responsible monitoring , control of movements of device.

an actuator mimics actions of muscle in producing force , movement. examples include motor aids or replaces original muscle tissue.

targeted muscle reinnervation (tmr) technique in motor nerves, controlled muscles on amputated limb, surgically rerouted such reinnervate small region of large, intact muscle, such pectoralis major. result, when patient thinks moving thumb of missing hand, small area of muscle on chest contract instead. placing sensors on reinervated muscle, these contractions can made control movement of appropriate part of robotic prosthesis.

a variant of technique called targeted sensory reinnervation (tsr). procedure similar tmr, except sensory nerves surgically rerouted skin on chest, rather motor nerves rerouted muscle. recently, robotic limbs have improved in ability take signals human brain , translate signals motion in artificial limb. darpa, pentagon’s research division, working make more advancements in area. desire create artificial limb ties directly nervous system.

robotic arms

advancements in processors used in myoelectric arms has allowed developers make gains in fine tuned control of prosthetic. boston digital arm recent artificial limb has taken advantage of these more advanced processors. arm allows movement in 5 axes , allows arm programmed more customized feel. i-limb hand, invented in edinburgh, scotland, david gow has become first commercially available hand prosthesis 5 individually powered digits. hand possesses manually rotatable thumb operated passively user , allows hand grip in precision, power , key grip modes.

another neural prosthetic johns hopkins university applied physics laboratory proto 1. besides proto 1, university finished proto 2 in 2010. in 2013, max ortiz catalan , rickard brånemark of chalmers university of technology, , sahlgrenska university hospital in sweden, succeeded in making first robotic arm mind-controlled , can permanently attached body (using osseointegration).

an approach useful called arm rotation common unilateral amputees amputation affects 1 side of body; , essential bilateral amputees, person missing or has had amputated either both arms or legs, perform tasks of daily living. involves inserting small permanent magnet distal end of residual bone of subjects upper limb amputations. when subject rotates residual arm, magnet rotate residual bone, causing change in magnetic field distribution. eeg signals electroencephalogram, test detects electrical activity in brain using small flat metal discs attached scalp, decoding human brain activity used physical movement, used control robotic limbs. essential being provides more lively affect robotic limb, giving oneself control on part if own.

robotic legs

robotic legs have been developed: argo medical technologies rewalk example or recent robotic leg, targeted replace wheelchair. marketed robotic pants .