Bionic Prosthetic Arms

ELEC 371 – Biomedical Instrumentation Seminar

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What do these activities have in common?

Motivation:

• Few activities and tasks we do are done without the use of our hands. They are an essential tool we use to navigate the world.

• “Being able to pick up dexterous items or even picking up something heavy [can be] a major [challenge]”. While seemingly mundane, to someone who has lost the use of their hand, tasks pictured above would be nearly impossible.

• Normal limb function can be (partially) restored through the use of prosthetics, improving quality of life.

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Hero Arm – Below elbow upper-limb

prosthetic

Flex-Run– Transfemoral and

Transtibial prosthetic

Total Hip Arthroplasty– replacement of damaged joint with

prosthetic components

Introduction:

Definition: • Prosthesis or Prosthetic implants are an artificial device used to replace a missing

Body part. • Broad term describing a variety of different devices for the body (THA,

transfemoral prosthetic, upper-limb prosthetic, etc.)• Functional goal is to restore the normal limb function.

Goal of this presentation:• Explore limb prostheses for the upper-extremities.• See how robotics and electromyography used enhance the restoration of normal

limb function. • Focused on: Hero Arm designed by Open Bionics.

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Ulnar

Radial

Median

Musculocutaneous

Scapula

Carpal

Metacarpals

Phalanges

Humerus

Ulna

Radius

Elbow

Bones

Nerves

Joints

Shoulder

Proximal Radioulnar

Distal Radioulnar

Wrist

Bones and Nerves of the upper extremities:

Nerves that innervate the upper-limbs:• Musculocutaneous nerve – muscles in anterior compartment of the arm.• Median nerve – flexors in forearm and Thenar muscles in the hand.• Radial nerve – all the muscles in posterior compartment of the arm and forearm.• Ulnar nerve – intrinsic muscles in hand, in addition to flexors in the forearm and

hand.

Joints of the upper-limbs:• Elbow joint:

• Humerus• Radius and Ulna

• Shoulder joint:• Scapula• Humerus

• Radioulnar:• Ulna• Radius

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• Wrist:• Radius• Bones of the hand

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Supinator

Pronator Teres

Pronator Quadratus

Arm Forearm

Muscles

Arteries

Veins

Biceps brachii

Brachial artery

Ulnar artery

Biceps brachii

Basilic vein

Cephalic vein

Radial artery

Muscles and Blood vessels of the upper extremities:

Muscles of the upper-limbs:• Biceps brachii • Supinator • Pronator teres • Pronator quadratus

Major blood Vessels that feed the upper-limbs:• Brachial artery• Ulnar artery • Radial artery• Basilic Vein • Cephalic Vein

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Hand Movements

Arm/Forearm Movements:

Finger Movements:

The Hand as a mechanical Tool:

Combo of muscles, nerves, and bones allow for a variety of movements at various joints of the upper-limb:• Flexion/Extension• Abduction/adduction• Pronation/supination

Major function: Grip and manipulate objects.

Performed through:• Flexing fingers against thumb• Modifying actions of forearm tendons• Combination of complex Hand/arm/forearm joint movements

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Cortical Sensory Homunculus

2D Representation 3D Representation

The Hand as a sensory Tool:

Second Major Function: Discern objects and physical properties of world through touch.

• The pads of the fingers contain a high density of sensory receptors. • sensory cortex of brain for interpreting information from the hand is

disproportionately larger than that for many other regions.• This is represented visually through a cortical sensory homunculus (both 2D

and 3D artistic representations on slide)

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Classification of Upper-limb amputations

Potential for pronation and supination of residual limbs

When is an upper-limb prosthetic used:

An upper-limb prosthetic can be sought or recommended to any individual with loss of upper-limb or upper-limb function.

This can occur for a variety of reasons, including:• Trauma (ex. Frostbite, tissue damage, etc.)• Disease (vascular disease, diabetes, infection, etc.)• Condition present at birth

Types and consequences:• Various classifications of upper-limb amputations (pictured above)• Longer residual limbs with transradial amputations results in more residual

forearm and hand rotation.

The Hero arm is designed for amputations occurring below the elbow.

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Hero Arm

Manual Wrist RotationOverview Thumb Flexion

What is the Hero Arm:

The Hero arm is a medically certified 3D-printed bionic arm for below elbow amputee adults and children.

Custom Built:• Each arm is custom-built using 3D printing and scanning technology.

• Scan/3D model of arm, feed through algorithms to generate individuals arm cad files, then print and assemble

• Open Bionics makes the hand, socket, and frame and delivers an all-in-one prosthesis custom for each client.

• This allows for dynamic sockets – Compressible and expandable, gives more comfort to wearer.

Control:• Uses myoelectric sensor to detect muscle movements for hand/grip control.• Multi-grip versatility – gives great user control. Can be reconfigured to your

preferences by your prosthetist.• Posable wrist – Manual wrist rotation 180 degrees.

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• Posable thumb – Assist in picking up small objects• Proportional control – Speed control of fingers slows for delicate tasks.• Freeze mode – The hand can be held in a static position without muscle

contraction input.

Feedback:• Provides notifications and feedback through haptics, beepers, lights, and buttons.

Performance:• Lightweight – The full prosthesis weighs less than 1kg / 2.2lbs.• Strong - Able to lift up to 8kg (strong when considering lightweight property).• All day battery usage.

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4 Motor Hand 3 Motor Hand

Use and Layout:

Intended use:The Hero Arm is intended to be used for light to moderate day to day activities that require the use of one or two hands, such as:• Holding objects (cups, tools, kitchen utensils, trays, bottles, bags)• Performing operations (opening doors, pressing buttons, getting dressed)

Arm layouts:• 3 different hand sizes and 2 different arm layouts as well as a 3 Motor or 4 Motor

Hand.• The 4 Motor version:

• 2 tendons on both the index & middle fingers, which allows them to move independently.

• 6 different hand grips/positions• The 3 Motor version:

• single tendons, index & middle fingers will always move together.• 4 different hand grips/positions

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Hook and Fist Grip

Tripod Grip

Pinch Grip

Usability:

Grip Patterns:• Grips are grouped together (in software) to make switching between them quick

and easy. • Switch between grips and groups through the use of the hand button and

relaxation of muscle signals• Light and haptic feedback will inform the user as to which group and grip pattern

they have selected.• The three grip “groups are pictured above, and have various alterations within the

finger movement.

Freeze Mode:• Used with any of the grip pattern to temporarily freeze the position of the hand

and disable the muscle control• allows position setting without sending a muscle signal (removes chance of

accidentally releasing grip).

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Prototype submitted to James Dyson Award (2015)

Guinness Book of Records (2018)

UAE AI & Robotics Awardfor Good (2017)

History of the prosthesis and hero arm:

Beginnings:• Open Bionics is a Bristol-based robotics start-up that got its beginnings in 2014.• It was Co-founded by Joel Gibbard and Samantha Payne.

• Initial prototypes won the UK’s James Dyson Award for Engineering in 2015.

• Awarded with a Wired Social Innovation Award in 2016.• Awarded with a Guinness world record.• In 2017, the company was awarded the UAE AI & Robotics Award for

Good, awarding the design with a $1 million prize. • This capital enabled the start-up to complete work on the

development of the Hero Arm.

Fun Fact: The company has worked with Disney to develop a range of Hero Arm covers with designs from the Star Wars, Marvel, and Frozen franchises; in addition to their collaboration with Eidos-Montreal on Deus Ex covers for the Hero Arm.

Continued Work:

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• The company is now also working with NHS England, the Bristol Centre for Enablement, Bath University, and Gyrobot on clinical trials.

• Following a successful first stage of the trial in June 2017 with 7 Bristol-based children, the company is planning a second stage of the trial with multiple NHS clinics around the UK.

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Method of controlling Hero Arm

Prototype Hero Arm electrodes

Controlling the Hero Arm:

• Advanced myoelectric sensors (which are not specified in detail publicly) in the arm detect your muscle movements, the hand responds with intuitive control.

• Prosthetist will find the optimal location of the EMG Sensors for your muscles. Different for each amputee

• The bionic hand is controlled by tensing the same muscles which are used to open and close a biological hand (large flexors/extensors of the forearm).

• To close the Hero Arm’s hand, and perform the selected grip, imagine flexing the wrist inwards while pulling the fingers into the heel of the hand.

• To open the hand, imagine extending the wrist with an outstretched palm.• The hand will move more slowly when your muscles are tensed gently, and

will move more quickly with a firmer tense. • This proportional control is useful for manipulating small or

delicate objects.

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How do Muscles initiate contraction:

Nerve cells propagate action potentials and conduct ions (K+ and Na+) in order to send information throughout the body, including to contract muscles.

• Cells at negative potential when resting(high Na+ outside, high K+ inside)• Adjacent cell reaches action potential increasing permeability to Na+.• Cell depolarizes, Na+ enters the cell• Action potential is reached, permeability to Na+ decreases and K+ increases.• Cell repolarizes and returns to resting potential• This creates partially polarized cell that propagates along neurons.

It is the summation of these current dipoles and neurons firing that generates a potential field that can be measured.

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Data capture and analysis

What is Electromyography and how do myoelectric devices work:

• Electromyography (EMG) is a technique for recording electrical activity produced by nerve cells when contracting skeletal muscles.

• Most simple method uses two electrodes (one as a reference) to measure the electric field.

• Two kinds of EMG, surface EMG and intramuscular EMG. • While open bionic is not public about their detailed design work, it is safe

to say that the Hero Arm does not use percutaneous electrodes, and therefore they utilize surface EMG.

• Most likely Non-polarizable electrodes, that consist of metal and a neutral electrolyte, that utilize ions to generate a electron current flow that can be measured.

• Data captured is then filtered, rectified, smoothed, and can then be used as a control signal for moving the motors in the hand in the Hero Arm.

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3D Printed Technology with Flexible Materials

Advantages of this Technology:

On top of returning a level of normal limb function, there are a few major advantages of the Hero Arm Design:

• 3D printed and customized to each patient:• Easier to manipulate and change based on needs of patients• Custom covers give patients an element of style choice• Higher availability of parts (plastic) and cheaper to produce

• Lightweight • The full prosthesis weighs less than 1kg / 2.2lbs.

• Affordable pricing • The Hero Arm is the most affordable (medically certified) bionic hand

available.• Not a surgical implant. Therefore the “procedure” has a high success rate if one is

eligible for trial, as each device is designed specifically for the patients needs.• Reduced Fitting time

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Designated for light-moderate

tasksOnly supports below elbow amputations

Disadvantages of this Technology:

Unfortunately with some of the advantages the Hero Arm has, it also comes with some draw backs:• Only supports below elbow amputees at the moment.• Grip strength not as strong as competitors at cost of keeping device at a light

weight.• Only designed for light-moderate “home” tasks• Wrist, and some thumb adjustments must be made manually.

• Challenges surface EMG exists, and may not be suitable for all users.• Independent control signals hard to determine with surface EMG

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$5,000.00 $11,000.00

$60,000.00

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20000

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Comparison of Cost

i-LimbbebionicHero Arm

Economics and logistics of the Hero Arm:

• Costs around $3000 - $5,000 • Not officially listed, but there are ranges listed in online sources.

• Far less cost than competitors, which can be as expensive as $120,000.• Only takes about 40 hours to manufacture one arm, much faster turn around time

than with other designs/competing technology.• Not available to everyone, still undergoing private continued trials (which you can

apply to be apart of)

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i-Limb by Ossur bebionic by ottobock

Brain-Computer Interface

Targeted Muscle Reinnervation

Competing or similar Technology:

Competing Devices:• i-limb line of devices from Ossur

• Gesture, App, Mucsle, and Proximity control• $60,000-$120,000

• Bebionic hand from ottobock• ~$11,000

Other Technologies:Surface EMG interface VS:• Targeted muscle reinnervation

• Spare Muscle reinnervated with residual nerves of the amputated limb, allowing EMG signals of the target muscle to now represent the motor commands to the missing limb.

• Multiple independent EMG signals produced vs. surface EMG devices like the Hero Arm.

• Cortical interfaces• Direct connection with cerebral cortex of the brain.

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• Microelectrode array• Peripheral nerve interfaces

• Bi-directional

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Questions

Questions (?)

Sources:

1. https://www.youtube.com/watch?v=luHmXHEpF7w2. https://en.wikipedia.org/wiki/Prosthesis3. https://www.ossur.ca/prosthetic-solutions/products/sport-solutions/flex-run4. https://orthoinfo.aaos.org/en/treatment/total-hip-replacement/5. Gray’s Anatomy for students (Third edition)6. https://teachmeanatomy.info/upper-limb/joints/7. https://en.wikipedia.org/wiki/Cortical_homunculus8. https://musculoskeletalkey.com/prosthetic-options-for-persons-with-upper-

extremity-amputation/9. [https://openbionics.com/hero-arm-user-guide/10. https://en.wikipedia.org/wiki/Electromyography11. “Biopotentials”, “EKG, EEG, & EMG”, “Bio-Potential Electrodes” – Dr. Stocco

(ELEC371 slides)12. https://en.wikipedia.org/wiki/Proportional_myoelectric_control13. https://www.youtube.com/watch?v=3nnrstBxomk

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14. https://www.techspot.com/news/79515-open-bionics-3d-printed-hero-arm-now-available.html

15. https://www.tctmagazine.com/3d-printing-news/open-bionics-wins-1-million-award-3d-printed-bionic-hands/

16. https://all3dp.com/open-bionics-receives-guinness-world-record-deus-ex-prosthetic-limb/

17. https://www.jamesdysonaward.org/en-CA/2015/project/open-bionics-3/18. https://en.wikipedia.org/wiki/Depolarization19. https://imotions.com/blog/electromyography-101/20. https://www.techspot.com/news/79515-open-bionics-3d-printed-hero-arm-now-

available.html21. https://www.youtube.com/watch?v=luHmXHEpF7w22. https://www.youtube.com/watch?v=3nnrstBxomk23. https://www.cnet.com/news/touch-bionics-i-limb-prosthesis-is-controlled-by-an-

iphone-app/24. https://passio.co.uk/2020/02/02/the-hero-arm/

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